ar v 16742 r CORNELL UNIVERSITY LIBRARY 3 1924 031 445 210 olin,anx Cornell University Library The original of tiiis book is in tine Cornell University Library. There are no known copyright restrictions in the United States on the use of the text. http://www.archive.org/details/cu31924031445210 THE DISCOVEEY NATURE OF THE SPLEEN, PEOM AN INVESTIGATION OF THE LATERAL HOMOLOGIES OF THE LIVEE, STOMACH, AND ESTTESTINAL CANAL. Efm HENEY E: SILVESTER, B.A,, M.D.Loiid., CLAPHAM COMMONj LONDONJ ASSOCIATE OF SING*8 COLLEGE, LONDON; AND FORMERLY HUNTERIAN SCHOLAR IN HUBIAN AND COMPARATTVE ANATOSTT IN THE ROYAL COLLEGE OF SURGEONS OF ENGLAND. Author of " The Discovery of the Physiological Method of inducing Bespiration in Cases of Apparent Death &om Drowning, Chloroform, Still-Birth, Noxious Gases." " The Physiological Method of Treating Incipient Consumption, with Directions for its Prevention." "A Contribution to the Science of Teratology/' etc. LONDON: JOHN CHUECHILL & SONS, NEW BUELINGTON STREET. mDCCCLXZ. " Thine eyes did see my substaace, yet being nnperfect; and in thy book all my members were written, which in continuance were fashioned, when as yet there was none of them." Fs. cxxxix, 16. ""Exet 5* 6 &vepcoiros Kal rh &va Kal rh Kdra, Kal irpoffflk Kal ontaeia, Kal 5e|ia Kai cLpiarepa. rci ixev o5c Sc|ia Kal apiarepa Sfioia trxeSckc iv Tois fiepeai Kal ravra ircEvra, xA.^v aadevefrrepa rh aplarepa," Abistot, ON THE ISTATUEE OF THE SPLEEN. The anatomy and physiology of the spleen have engaged the attention of philosophers from the days of Hippocrates down to the present time ; there are, indeed, few parts of the human body on which more has been written than on the spleen, and none where the result has been more un- - satisfactory. It becomes us, then, to approach this subject with due consideration. Haller, in beginning his observa- tions, very sensibly admonishes his readers that "he is plunging into the region of mere conjecture, darker than in the case of any other viscus." A short historical re- capitulation of the various theories respecting its functions will introduce us to some of the obscurities which require to be elucidated. It wUl, however, be unnecessary to dwell upon a vast number of hypotheses ; for part of them are entirely destitute of anything like proof, and others are contradicted by experiment. The most ancient opinion concerning the use of the spleen in the animal economy is that found in the writ- ings attributed to Hippocrates, and is connected with the famous doctriae of the four humors (Hippocrates, 4:th Book, Be Morb., torn, ii, page 325, ed. Kiihn) Tip fiev Srj ai/xaTi rj KapSirj Try/^ cVtJ ti5 Be (jjkei^fiaTi r) Ke(l>aXrj Tip Se vBari o ff^XTjv. Ttj Be XoXij to '^ivptov to eyrl ti5 ^irwTt avTai at rdcFaapes Tovreoiaiv etiri Trrjr^ai avev t^s icoCkLq^. The heart is the source of the blood, the head of the pituita, the spleen of the water, and the liver of the bile. The water was attracted by the spleen from the fluids received into the stomach, 01/^2 he iir^v 6 avdpunro^ Trivrj jrXeov e\Keii> e's eiivTOv tic T^s KOiXirjs ^ov v&mos Kal to au>p.a Kal tov airXrjva. (J6ic?.,p. 333.) In modern times, Charles Estienne 4 THE NATUEE OF THE SPLEEN. supposed the vasa brevia distended with blood to be ducts proceeding from the spleen to the stomach, carrying fluid fr9m one organ to the other. This opinion was soon after- wards set aside by the accurate observations of Vesalius, {Opera omnia Anatomiea, Lugdun. Batav., 1725, pp. 437 to 440) ; and Sir Everard Home revived the old theory of Hippocrates, and made the spleen to receive a great por- tion of our drink from the cardiac extremity of the stomach. It was supposed to be transmitted directly from the stomach to the spleen by some unknown channel. This idea, how- ever, after a series of experiments with coloured fluids, etc., he subsequently abandoned. In another part of the Hippocratic collection {De loc. in Horn., tom. ii, page 130) it is said that Toiat r^ap avtounv oTeo airX'^v OaXXet Kal to ir&fm (pOivei — those persons whose spleen is large have their bodies meagre — and which gave rise to the well-known comparison of Trajan, who said that the imperial treasury was like the spleen, because when that was rich the people were impoverished. " Namque ut ceteras omittam, Pompeia Plotina, incredibile dictu est, quanto auxerit gloriam Trajani ; cujus procuratores cum provincias calumniis agitarent, adeo et unus ex iis dicere- tur locupletium quemque ita convenire, Quare habes? alter unde habes 1 tertius, Pone, quod habes ; ilia conju- gem oorripuit ; atque increpans quod laudis suse asset in- curiosus, talem reddidit, ut postea exactiones improbas detestans, fisc'um lienem vooaret, quod eo crescente, artus reliqui tabescunt." (Sexti Aurelii Vict oris, epitom., cap. xlii, sec. 21.) The probable explanation of the observation, which has been confirmed in modern times, that the spleen is large when the stomach is filled with fluid, is to be found in the circumstance that the circulation through the spleen is liable to be obstructed by a congested condition of the portal system. The symmetrical arrangement of the external organs of the body must be obvious to the most superficial ob- server. Symmetry expresses a fact; namely, that one half of an animal is usually an exact reversed copy of the other. The internal organs, also, are symmetrical. The term azygos (afwyis) is applied by anatomical writers to certain parts of the body, which, being situated in or near the mesial line, appear singly and not symmetrically, THE NATURE OP THE SPLEEN. 5 or in pairs. This term, however (strictly speaking), is in- correctly applied; for each of these organs is composed of parts that were originally double or symmetrical, and which have coalesced in the middle line so completely as to appear single. The celebrated Greek philosopher Aristotle draws atten- tion to this arrangement of the animal body in his treatise J)e Animalibus Historiae, lib. i, cap. xv : "Exet b' o avdpwiro^ Kal TO aval Kal to KtvTui, icai. wpoo6ia Koi oirlaOia, ical Se^ia Kal aptffrepa, ra fiev ovv be^ia Kai apiarepa ofjioia ff'^edov iv TOts tiepeGi Kai ravTa TravrUj ttXtjv aoQeveoTepa ra aplatepa. Man, however, has the parts of his body distinguished as the superior and inferior, the anterior and posterior, and the right and left. The right and the left parts, therefore, are similar and nearly the same, except that the left parts are less developed ; and in De Fartibus Animalium, lib. iii, cap. vii, Aristotle says : " koto he to rjirap Kal tov airXr/va SiKatws av Tte awoprjaetEV' tovtov S antov OTi ev /lev 70?s e^ ovafyicnff e'^ovtri oirXtjva Bo^etev av oiov voOov etvaL TjTrap o aTrXrjv." With respect, however, to the liver and spleen, it may be justly doubted whether they are bilateral or not, the cause of which is that in those animals that neces- sarily have the spleen, it may appear that the spleen itself is, as it were, a spurious liver. Again, in lib. iii, cap. iv, he says : "Swap — e'^ei S" uiairep avTi^v^ov ev toTs fioKia-i mrriKpifiw/ievots rbv uTrX'^va. The liver — but in the most accurately formed animals it has the spleen, as it were, opposite to it. If, then, the spleen is symmetrical with the liver, why is there any need of discussion about it 1 Why is this not conclusive evidence that the spleen is the imdeveloped Hver of the left side of the body, and if it is the undeveloped liver of the left side, may it not be sup^ posed to assist in the function of the liver — namely, the secretion of bile ? These questions, amongst others, will require our attention further on. With regard to the function of the spleen, Aristotle says that "It is not an organ necessary for all animals, and that it assists the Hver in performing the function of di- gestion ; that the spleen attracts from the stomach the superfluous and excrementitious humours (chyle) and con- cocts them." Plato, in the Timceus, makes mention of the spleen, and b THE NATURE OF THE SPLEEN. says : " On this account, when certain impurities are pro- duced about the liver through bodily disease, then the spleen, purifying these by its rarity, recejves them into itself, from its being a hollow and bloodless contexture." Diodes of Caristus, who flourished a little time after Aristotle, confirmed the statements which his predecessor had advanced. A period of repose ensued for several cen- turies, until two celebrated anatomists arose in the Alex- andrian school who, favoured by the permission of Ptolemy Lagus, the first of the Egyptian princes, with diligent re- search elaborately dissected the human body. These were the celebrated Herophilus, and Erasistratus, the pupil of Chrysippus, his contemporary, and were the means of giving to anatomy the rank of a true science. It is sur- prising that so eminent an anatomist as Erasistratus, not- withstanding these advantages, and while confessing that nature does nothing without a reason, should, neverthe- less, consider the spleen to be a useless organ, an opinion adopted also by Eirfus Ephesius, and apparently by Pliny, who says that runners used to have their spleen removed in order to increase their speed. The followers of Erasis- tratus dissented from this opinion of their master, and said that the spleen first prepared the chyle, which the liver afterwards turned into blood. The opinion of Galen was that the humour called black bile is secreted by the spleen in the same way as the yellow bile is secreted by the liver, and it was from the supposed accumulation of this humour that persons aifected with melancholy were believed to sufier. " Galen's opinions received universal assent, not only from the physiologists of his time and the Arabians, Avicenna, etc., but prevailed throughout the ages of darkness and barbarism, and were even defended by those anatomists who lived in the com- mencement of the sixteenth century at a time when science and literature were again revived, and when the intellectual powers became again roused after a repose of more than a thousand years" (Gray). In the works of Aretseus, there is no fresh addition to our knowledge of the anatomy of the spleen ; but his opinion, which is held in a modified form even at the present day, is that the spleen is nourished by black blood, of which it is the receptacle, and that, when, it is THE NATURE OP THE SPLEEN. 7 diseased, this fluid is not elaborated by it, but is taken into tbe general circulation. He, in effect, separates the function of the spleen from that of the liver, and regards' the spleen as a blood-gland. Serenus Samonicus seems to consider the spleen as the organ of mirth, and that after its removal a person never laughed. " Splen tumidus nocet, et risum tamen addit ineptum, TJt miM Sardois videatur proximua herbia, Irrita qusd miseris permiscent gaudia fatis. Dicitur exseotus faoiles auferre cachinuos, Perpetuoque sevo frontem praestare severam." It seems, at first sight, strange that, as the organ was considered to be the seat of mirth and laughter, the words spleen, spleenful, splenetic, etc., should be commonly used now to signify exactly the contrary state of mind. This opinion has probably arisen, first, from the spleen hav- ing been supposed to secrete the black bile, ftAXaiva xo\^, whence the word melancholy is derived ; and secondly, from its having been considered as one of the causes of melancholy when " he doth not his duty in purging the liver as he ought, either too great or too little in drawing too much blood sometimes to it, and not expelling it" (see Burton's Anatomy of Melancholy, part i, sec. 2, men. v, sec. 4, and elsewhere). Oribasius, Alexander Tralhanus, Paulus.^gineta, Joannes Actuarius, Haly Abbas, TheophUus Protospatharius, and Meletius agree with Galen concerning the functions of the spleen. According to Avicenna, the spleen by its vasciilarity imparts warmth to the stomach. Hofinan mentions that some of the Arabic writers con- sidered the office of the spleen to be to cool and refresh the heart. In other ancient writers, as, for example, St. Ambrose {Hexaem. lib. vi, sec. 71), " we find a slight modi- fication of Galen's opinion ; viz., that the spleen is placed near the liver in order to draw away the useless part of the aliment, and so, after retaining that which is necessary forits support, to transfer the purified and subtle remainder through the liver to the blood." (See Penny Cyclopaedia.) Joh. Guinterius follows Galen's description — "corpus hujus visceris, quod parenchyma vocant, rarum et laxum est spongise modo, ut facilius crassos humores et jecoris aUiciat." 8 THE NATUEB OF THE BJPLEifiJM. " Charles Estienne supposed the vasa brevia distended with blood to be ducts proceeding from the spleen to the stomach — an opinion soon afterwards set aside by the ac- curate observations of Vesalius. About 1578, a new theory of its use was suggested by Franciscus IJlmus in his Monograph, the first published on the anatomy of this gland, a theory, however, not founded on extended ob- servations on the anatomy of the organ. He supposed that its office was to prepare blood for the heart and arteries, the material from which it is formed being the chyle, which is brought from the stomach by a large vein (the gastric) to the spleen by a branch of the vena portse, the formed blood being returned to the heart by the splenic artery and aorta. Fel Plater also believed that its office was rather the elaboration of blood than the attraction of the melancholic juice, although he explained the me- thod by which the blood was elaborated differently from IJlmus. He also argued that, as all azygos parts are placed in the median line of the body, the spleen cannot be one, as it corresponds in situation and structure with the liver, and therefore must be the liver of its own side, an opinion which he attempted to prove by many argu- ments." (Gray.) It is unnecessary here to enumerate the various modem hypotheses, which are mostly fanciful and imaginary. It will be seen from the foregoing, that the more important theories concerning the nature of the spleen maybe placed in two divisions : — in one in which the spleen is to be re- garded as essentially connected with the liver, both func- tionally and anatomically, being the liver of the left side of the body, and this theory rests mainly for support upon the law of symmetry ; and, in another division, where the spleen may be considered to be a blood-gland, having little or nothing to do with the liver either ftmctionally or anatomically, its function being the elaboration of the sanguineous fluid. The liver in this case is regarded as an azygos and symmetrical organ, the left side being but slightly developed ; and the spleen is looked upon as par- taking of the nature of a lymphatic gland, not symmetri- cal with the liver, but a mesial organ, and as an appendage of the sanguiferous system. One great difficulty in demonstrating that the spleen is THE NATtJEE OP THE SPLEEN. 9 the liver of the left side is, that the spleen cannot in any case be proved, to secrete true bile ; whilst the difficulty in the other supposition is, that the liver cannot be shown to be a symmetrical or azygos organ. In modern times each division has found an advocate. Doellinger is in favour of the spleen's being regarded as symmetrical with the liver ; and Miiller regards it as a blood-gland. The greater number of modern physiologists appear to have followed Miiller, and the study of the rela- tive position and form of organs which had been the almost exclusive task of the elder school has now been thought to be of comparatively slight importance ; whilst the in- timate composition of all the organs has been investigated with unparalleled zeal and singular success. Doellinger says : — " Symmetrisch mit der Leber bildet sich das Milz, ein theils an und fiir sich, theils in seinem Verhaltnisse zur Leber, besonders merkwurdiger Theil. Die in dem Sacke des Bauchfells eingeschlossenen Einge- •weide zeichnen sich durch Mange} an Symmetrie aus, und so ist denn auch die Leber selbst unsymmetrisch gestaltet und insbesondere nicht gepaart. Der Leber gegenuber befindet sich das Milz und die Bauohspeicheldriise, welche an die Stelle einer vollendet symmetrischen Paarung der Leber zu treten scheinen. Auf der linken Seite des Darm- kanals ware sohin in zwey TheUe getrennt, was auf der rechten in ein Eingeweid vereinigt ist ; eine Trennung wozu sich mehrere Beispiele auch an andern Theilen aus der vergleichenden Anatomie anfiihren lassen. Mann kann die Leber fur eine Vereinignng des Milzes und einer Speicheldriise ansehen, Mann kann aber auch sagen, es habe sich in der linken Seite der Unterleibshble das Parenchyma der Leber und die ausfuhrungs-gange dersel- ben getrennt aus jenem sey das Milz, aus diesem die Bauohspeicheldriise enstandenWahrscheinlichgiebt hierzu die herrschende Magenbildung den Anlass. An und fiir sich ware also das Milz ein Product der unvollstandig symmetrischen Bildung, und einer durch aussere Bestim- mungen herbey gefuhrten Trennung ; woraus man ein- sieht, warum keine absonderung, wenigstens keine aus- fuhrung in ihm geschehen kijnne. Ist einmal das Milz .enstanden so hat es zur Leber in so feme die Milzvene als ein ast zur Bildung des Pfortaderstammes beytragt, kein 10 THE KATUEB OF THE SPLEEN. anderes Verhaltniss als die iibrigen Eingeweide des Un- terleibs. Man denke sich doch keinen zweck wo keiner iat." Grundriss der Naturlehre des Menschlichm Organis- mus. Von Ignaz Doellinger, M.D., 1805. Miiller, in his Elements of Physiology, classifies the spleen with the suprarenal capsules, the thyroid and thy- mus gland, as was originally suggested by Ruysch, who also arranged the liver under the same category. He says : — " These are glands unprovided with an efficient duct ; they agree in having the common function of im- pressing some change on the blood which circulates through them, or in yielding a lymph which plays a special part in the process of chylification and sanguification ; for the venous blood and the lymph are the only matters re- turned by them into the general system." " The spleen is met with only in the vertebrate classes, and in them it is nearly constant. In the cetacea the organ is divided into several smaller masses. In man and mammalia the spleen lies in the fold of peritonaeum, which is continuous with the serous covering of the ante- rior and posterior surface of the stomach, and extends be- tween the great curvature of the stomach, the diaphragm, and the transverse colon, and which at the part where it connects the stomach to the transverse colon is called the great omentum. This portion of peritonseum passes origi- nally from the spinal column in the middle line to the great curvature of the stomach, forming a mesogastrium in which the spleen was developed. The spleen, therefore, is not an organ proper to the left side of the body, of which the fellow of the opposite side is wanting. It should be regarded as an organ originally situated in the middle line, just like the liver, which at first, when its two lobes were equal, did not belong to the right side more than to the left." And again : " AH the theories which regard the spleen as essentially connected in its function with the liver can be shown to be fallacious. Doellinger supposes the spleen to be formed merely for the sake of symmetry to be the fellow of the liver, — the rudimentary liver, as it were, of the left side. But the liver is originally symmetrical; and the spleen is, as we" have already described, developed in the middle line — no greater value can be accorded to THE NATURE OP THE SPLEEN. 11 the circumstance that the splenic veins join the vena portse, and the hypothesis thence deduced that the spleen pre- pares the blood for the secretion of the bile ; for, in this respect, it does not differ from all the chylopoietio viscera, nor even from the inferior extremities in the lower verte- brata and the generative organs and air-bladder of fishes. We know that its importance in the economy is not great." Miiller's assertions appear to have obtained universal acceptance; though, on further inquiry, they will be found singularly unfortunate ; and he concludes them by ad- mitting that we are still ignorant of the office of the spleen. The inability to assign any function to this organ is, pro- bably, a reason for grouping it with other ductless glands. Again, it is quite a different thing for an organ to be formed symmetrically with another and to be formed merely for the sake of conforming to the law of sym- metry. In mammalia the large size of the splenic artery (frequently the larger branch of the cseliao axis) and vein, and the great pathological changes which are known to occur in the spleen, negative the idea of the spleen being formed merely for the sake of symmetry; moreover, that the spleen is an useless organ, or even one of little importance, is not established by the fact that important results do not follow upon its removal ; for the removal of a kidney, a lymphatic gland, an ovary, a breast, an eye, an ear, etc., is not attended with serious consequences. Miiller asserts that the liver itself is a symmetrical organ. Now, if this could be proved, nothing would be wanting to complete the idea of symmetry; but of this, more here- after. Again : the spleen, he attempts to show, is developed in the middle line; nevertheless, he groups it with the supra- renal capsules, — lateral organs,- — and he brings to his aid for this purpose the dispositions of the peritonseum ; he could not have chosen a more fallacicius guide. The peri- tonseum itself is evidently unsymmetrical ; moreover, the situation of the spleen varies considerably in the verte- brate series, being sometimes attached to the liver or to the pancreas or bound to the transverse arch of the colon or placed behind the stomach, etc. Again : if the spleen be, as h'e asserts, developed in the middle line of the body. 12 THE NATUEB OF THE SPLEEN. it ought itself to exhibit a bilateral symmetry, which, how- ever, it does not; and, Miiller having claimed for the liver a mesial position, on the assumption that it is a symme- trical organ, it is incumbent upon him to show that the spleen is also symmetrical. With regard to the observa^ tion, that in the oetac'ea the organ is divided into several small masses, we have it on the authority of Gray, that, in the great northern whale {Balena mysticetus) this organ is single ; in the porpoise, no doubt, there are several spleens ; and in the dolphin the spleen has many lobes. Miiller discredits the hypothesis that the spleen prepares the blood for the secretion of the bile on the ground that the splenic vein joins the vena portsB, as do also the veins of the inferior extremities, in the lower vertebrata ; but why the spleen may not, on this account, aid in this function, does not appear; and its vein joining the vena portse, which is admitted to be instrumental in the biliary function, is favourable to the view that it may, in com- mon with it, assist in this important matter. It must be evident, then, from the foregoing observa- tions that, in order to elucidate the nature of this myste- rious organ, two subjects must be investigated ; namely, the symmetrical arrangement of the organs of the body and the nature of the function of the spleen. Let us consider, in the first place, the question of sym- metry. Pittard is an advocate in favour of the symmetry of the abdominal viscera. His views, indeed, appear almost identical with those of Miiller. He says : — " The hepatic attachments of the falciform ligament and the gastro- splenic omentum land-mark the original median line of the liver, and that larger part of which is to the right of the ligament, and behind the omentum is the right lateral homologue of that lesser part which is to the left of the ligament and in front of the omentum. The anterior wall of the stomach is the left lateral homologue of the posterior wall. Tfie spleen is an originally mecdan organj situated in the originally median meso-gastrium. The great omentum is a pouching out of the meso-gastrium to- wards the left ; consequently, its outer surface is the left lateral homologue of its inner surface. The pancreas is an originally median organ, one end of which has been displaced along with the pylorus towards the right, so THE NATURE OF THE SPLEEN. 13 that its anterior aspect is the left lateral homologue of the posterior. Passing now from the regions of specu- lation, the intestinal canal can be witnessed in the em- bryo as a straight, uniform, mesial, and symmetrical tube, until its length, having become greater than that of the region which it is destined to- occupy, it is com- pelled to arrange itself in gyrations and loops. The pos- terior and anterior walls of the stomach were originally, as indicated above, its right and left halves, and as to the other parts of the alimentary tube, whatever difficulty there is in recognizing the manner of their displacement in the human subject, is at once dispelled by examining their condition in the lower animals. No difficulty what- ever is encountered in respect of the small intestine, for the mesentery is attached nearly in the median line. The bowels themselves, however, are continually varying their position, relative and positive, according to the manner of packing most convenient for their variable contents. Not so easy is it to understand the kind of displacement which has taken place in respect of the large intestine. The colon is curled back and crosses over the small intestine from right to left, forming a loop. In the human subject the true relation of these parts is further marked by the singular circumstance of this crossing over occurring just at the point where the meso-g&strium, after having de- scended as the great omental bag is returning to the spine, and the colon finding it there, so to speak, avails itself of it and uses it as a mesentery. Anatomists have named the borrowed portion of the meso-gastrium, the transverse meso-colon. In Ruminants, the colon being exceedingly long, avails itself also of the mesentery of the small in- testine into which a loop of it is thrust further . and further, until it makes three turns, so that in tracing the colon onwards with the finger, you make the spiral turns in the mesentery, and then double and return by the spiral turns placed between the former spirals. On the other hand, in the Carnivora, where the colon is very short, it crosses over the lower end of the ileum, so near its termination, that it is evident that the next degree of shortening mvist result in the continuation of the small and large intestine in a straight line. This actually takes place in the Keptilia, and then there is no longer any 14 THE NATDKB OF THE SPLBBJN. difficulty in recognizing the original mesial and symme- trical position of the intestinal tube, and its appendages, so displaced in the human subject as to make this recog- nition so extremely difficult." It is only necessary to say here that the above specula- tions in favour of the symmetrical arrangement of the ali- mentary canal and its appendages rest too much upon the fallacious guide — the dispositions of the peritonaeum ; it must be evident that these dispositions vary in accord- ance with the variable situations of the organs it envelopes. The viscera being in all cases outside of the peritonseum, a much more trustworthy guide wiU be found in the struc- tural form of the organs themselves, in their development, their vascular supply, their nerves and lymphatics, and their various forms in the vertebrate series. Having presented to our readers the above views in sup- port of the symmetry of the alimentary canal and its ap- pendages, we now proceed to collect evidences of want of symmetry. I may here just cite a few most notable exceptions, from comparative anatomy to symmetrical development. In Mammalia. — In the male narwhal the left incisor tooth attains the enormous length of eight or ten feet ; while the right one is found as a rudiment that never pierces the gum. The left nostril of most of the Cetacea is constantly much larger than the right. In Aves a most remarkable exception to symmetrical development exists in the female generative organs. The left ovary and oviduct alone are functionally evolved ; whilst the right, being atrophied at an early period, are barely appreciable in the adult animal. In Reptiles. — The lungs of reptiles are usually two symmetrical organs ; but in Ophidia the left lung, when it exists, is much shorter than the right ; and, in some, as Coluber thiringicus, it is wanting altogether, the only vestige of it being a csecal depression on the left side of the lower end of the trachsea ; the absence of the left lung entails, of course, the loss of the left pulmonary vessels. There can be no doubt that the left side of the human body is somewhat less fully developed than the right side. Again, the want of symmetry which is apparent in the great abdominal viscera and their appendages has been attempted THE NATURE OP THE SPLEEN. 15 to be explained by supposing that it depends entirely upon the lateral displacement and excess of growth of one side over the other, having reference to convenience of packing. This a-symmetry is greater in mammalia than in reptiles and fishes on account of the presence of the diaphragm which, so to speak, thrusts the abdominal viscera down- wards, necessitating lateral displacement, &c. ; it attains its greatest acme in man, owing to the great lateral measure- ment compared with the antero-posterior distance which is so conspicuous in his figure when contrasted with that of the other animals. Now this idea will be entirely dispelled by an examination of the minute anatoriiy of the various organs, and by such an instance of want of symmetry as is presented by the gall-bladder, (fee. I conclude it will be conceded at once that the cerebro- spinal axis, the respiratory, urinary, generative and san- guineous systems are symmetrical. It may, in the first place, be noted that those portions of the nervous, respiratory, uriniferous and reproductive systems which are situated at the sides of the body are represented by distinct unilateral organs, ,but those parts which are situated in the mesial line are bilateral and symmetrical, whether they are divided by a septum, or have their cavities freely opening into each other. To proceed, then, with the anatomy of the digestive system. The upper part of the alimentary canal as far as the commencement of the stomach is strictly symme- trical. The frenum connects the lips with the gums, and marks the union of the two sides. The vertical line on the middle of the lower jaw indicates the original division of the bone into two lateral parts. The raph6 along the middle of the whole length of the tongue indicates its bilateral symmetry, and at the base of the tongue, and in the midst of the muscular substance, will be found a ver- tical layer of fibrous tissue, which forms a partial septum between the two .halves "of the organ, and in the dog tribe a fusiform fibro-cartilage is known to exist in the middle of the tongue, near its under surface. The arteries of the tongue, derived from the linguales, are on each side of the septum. In the middle line of the hard palate is a ridge which marks the junction of the bones, and the soft palate is marked by a slight median ridge, which descends 16 THE NATUBE OF THE SPLEEN. towards the uvula, and indicates the original separation of the velum into two lateral halves. The salivary glands also are similar, and the pharynx and oesophagus are each composed of two precisely similar lateral halves, and each side is supplied with vessels from the corresponding side of the body. At the junction of the oesophagus with the stomach the symmetrical arrangement suddenly ceases. Some expla- nation is here required. It is to be noted that an organ may be apparently only developed symmetrically, that is to say, the anterior part may correspond with the posterior part, as, for instance, the anterior portion of the kidney may correspond with the posterior part of the same kidney ; but the anterior part of the kidney is not the homologue ' of the posterior part ; for the right kidney is the homologue of the left kidney. Just so in the stomach; the anterior, wall of the stomach, even if corresponding accurately with the posterior wall, is not therefore the left lateral homo- logue of the posterior wall. It will be found, on exami- nation of the process of development of the stomach, that the right or pyloric side of this organ goes on developing, whilst the left side or great end terminates in a large cid- de-sac ; so that the oesophageal opening is much nearer the great than the pyloric end, and the stomach consequently extends across to the right side of the abdomen beneath the liver and the diaphragm. The muscular and mucous coats will be found developed' accordingly, being thinnest in the great cul-de-sac and thickest at the pyloric end. The outermost layers of muscular fibres radiate from the oesophageal orifice, and are found in greatest abun- dance along the lesser curvature towards the pylorus; they are arranged closely together and form a thick uniform layer, which becomes continuous with the longitudinal fibres of the duodenum ; the second set, or the circular fibres, surround the body of the stomach with large circles, but at the left extremity of the great cul-de-sac they be- come small and thinly scattered rings ; towards the py- loric end they again form smaller rings, and at the same time become much thicker and stronger than at any other point ; at the pylorus itself they are gathered into an an- nular bundle, which forms the pyloric sphincter. The innermost layer, or the oblique fibres, descend obliquely THE NATUBB OP THE SPLEEN. 17 tipon the anterior and posterior surface of the stomach, where they spread out from one another, and gradually disappear. The gastric mucous membrane is thickest in the pyloric portion of the stomach, and thinnest in the great cul-de-sac, and the tubuli are shorter, and are simply tubular ; but on approaching the pyloric portion they gradually become larger, and assume a more complicated form, for, though quite straight near the orifices, they axe convoluted, or irregularly sacculated, towards their deep or closed extremities, and these characters are most per- fect near the pylorus. The lenticular follicles, though found in greater or less numbers all over the stomach, are most numerous towards the pylorus. We find that the azygos, or mesial, organs, are supplied by two vessels from the corresponding sides of the body; but when we examine the stomach we at once detect an exception, for although it is a highly vascular organ, the aorta gives off only one artery to the stomach, the coro ■ nary ; when, however, this artery is not given off directly from the aorta, it is associated in its origin with the hepatic on the right to the liver, and the splenic artery on the left to the spleen. The lymphatics of the stomach may be arranged in three sets : one set accompanies the coronary vessels, and receiving, as it runs from left to right, branches from both surfaces of the organ, turns backwards near the pylorus to join some of the larger trunks ; another series of lymphatics, from the left end of the stomach, takes a different course, and follows the vasa brevia, and unites with the lymphatics of the spleen ; whilst the third set inclines from left to right, along the great curvature of the stomach, from which it passes backwards, and terminates in one of the principal lacteal vessels. The prevertebral portion of the sympathetic system of nerves comprises three large aggregations of nerves, or nerves and ganglia, situated in front of the spine ; they are single or imsymmetrical. The coronary, or stomachic plexus, consists of numerous filaments, which are enclosed within the small omentum, and are guided by the coronary artery to the stomach. They form an interlacement by branches of communication one with another, also with 18 THE NATURE OP THE SPLEEN. the terminal branches of the pneumogastrio nerves, and finally spread out on both surfaces of the stomach. We must now direct attention to the state of the stomach in the vertebrate series, from which it will be apparent that, whilst the pyloric portion remains pretty Qonstant in form, it is distinct from the cardiac end, both' anatomically and physiologically. In mammalia. In the quadrumana the stomach often resembles that of man, but it is sometimes globular, or elongated, sacculated, constricted, or bent on itself; but whatever is the shape, a distinction between a cardiac and a pyloric portion is always recognisable. In the carnivora the stomach also presents the human shape, but the cardiac pouch is larger. In the insectivor- ous cheiroptera the stomach is globular. In the vampire, although it is long and conical, the cardiac end is the larger. In the frugivorous species it is still longer ; the cardiac pouch is constricted in its middle, and the pylorio portion is bent. In the proper insectivora this organ is elongated. In the edentata it is usually simple ; but in the genus manis the cardiac and pyloric portions are marked off by an internal fold, and in one species a long sac extends from the pyloric portion. In the sloth the stomach is first divided into a cardiac pouch and a pyloric. portion, the former has a dense epithelium, and is again subdivided into two parts, one ending in a blind canal. The pyloric portion has thick walls and a soft mucous membrane, and is subdivided into parts which might be compared with the third and fourth stomachs of ruminants. In the ant- eater the cardiac part of the stomach constitutes a kind of crop, whilst a second chamber, having thick walls and a hard gristly lining, somewhat resembles the gizzard of the bird, and compensating for the want of teeth, crushes the ants by aid of the sand swallowed with them. In ruminants the stomach presents the most remarkable complications. The cardiac end, variously subdivided and modified, is often lined by a thicker epithelium, but as it has been regarded as a dilatation of the oesophagus, we shall not dwell upon the description. In the pachydermata, the stomach is more simple : thus it is elongated, and possesses a long cardiac pouch in the elephant and rhinoceros ; but in the former it presents THE NATURE OP THE SPLEEN. 19 numerous internal transverse folds; the hippopotamus has two cardiac pouches opening widely into the rest of the stomach. In the tapir and hyrax this organ forms two cavities. In the pig the stomach resembles that of man, though the cardiac end is more projecting, and a consider- able extent of the lining membrane, near the oesophageal opening, is covered with thick epithelium. In the peccary still more of the cardiac portion is lined with a dense epithelium. In the solipeds the stomach is rounder, the oesophageal and pyloric openings are near to each other, and the cardiac portion is lined by a thick epithelium, which terminates in a dentated margin. In the rodentia the stomach is often marked off by a cardiac, and a pyloric portion, often indicated by an external constriction. Marsupials have a simple, somewhat elongated stomach. In the kangaroo the stomach is as long as the body, and the middle portion is sacculated, and marked by three longitudinal folds. It has three compartments, two being cardiac pouches, and also three rows of large crypts, along the bands. Among cetacea the dugong has this organ elongated, and marked off into a cardiac and a pyloric portion by a con- striction, from near which two blind pouches proceed. In Birds. — The digestive canal is usually complex ; the oesophagus being more or less dilated near its lower end to form the crop to which succeeds the proventriculus, or proper secreting stomach, and beyond this is a third cavity, forming the gizzard. The crop is most developed in the grain-eating gallinacea, forming a dependent bag connected with one side of the oesophagus, as in the fowl, or as in pigeons, consisting even of two lateral oval sacs. The second, or lower oesophagus, has no constricted cardiac orifice. The proventriculus, the true glandular stomach, varies in form, being sometimes wide and straight, some- times round. The gizzard is the third, or muscular stomach of birds. A pyloric valve usually exists in birds. In Reptiles. — The alimentary canal in this class is more simple than in birds, to which, however, it approaches more nearly than to that of fish. The oesophagus, as in birds, joins the stomach without any constriction or car- diac orifice. In the large saurians, the first part of the stomach has the form and structure of the gizzard. The pyloric part is more decidedly glandular, and corresponds 20 THE NATURE OP THE SPLEEN. with the short portion sometimes found between the gizzard and the duodenum in birds. In the serpents the cardiac part of the stomach is long, slightly sacculated, and highly dilatable, whilst the pyloric portion is narrower, and very muscular, being the only part like a gizzard. In the ohelonians the stomach is curved, and larger at the cardiac than at the pyloric end. The pyloric valve is usually present in reptiles, though not very distinct. In amphibia the stomach is fish-like, being tubular, wider at the cardiac than at the pyloric end, and placed trans- versely or curved upon itself. In Fishes. — The alimentary canal presents its most simple vertebrate form, being wide and short. The oesophagus, short, wide, and muscular, sometimes passes so evenly into the stomach, that the structure of the mucous membrane alone distinguishes them. In the cyclostornata it forms only, a dilated portion of the nearly straight canal. In the osseous fishes it is usually tubular, bent once upon itself, and narrower towards the pylorus^ sometimes it becomes flask-shaped, or globular, with its cardiac and pyloric openings placed near together; the cardiac orifice is large, and sometimes provided with a valvular fold ; the pyloric part is sometimes so muscular as to resemble an imperfectly developed gizzard ; a pyloric valve nearly always exists. In the singular amphyoxuB the alimentary canal is short, and nearly straight, the stomach being scarcely dilated. (Marshall). All through the vertebrate series there are clear indica- tions that the stomach is composed of two parts, physio- logically distinct from each other, a cardiac and a pyloric stomach, more or less united in the mesial line. The pyloric stomach remains in a very uniform condition, whilst the cardiac stomach assumes various forms. The cardiac stomach we regard as the homologue of the pyloric stomach, but remaining in a condition of incomplete development— the cardiac stomach being unprovided, at its left extremity, with a valvular apparatus resembling the pylorus. » We now pass on to the consideration of the anatomy of the intestinal canal. The small intestine is usually regard- . ed as occupying normally a mesial position, and this is supposed to be rendered certain by the consideration that THE NAT ORE OF THE SPLEEN. 21 the mesentery is attached nearly in the middle line. There is nothing, however, in the small intestine which indicates a symmetrical arrangement of its parts ; the patches of Peyer's glands are placed lengthways in the intestine, at that part of the tube most distant from the mesentery; but the patches are neverplaced symmetrically on each .lateral aspect of the bowel, and the other glan- dular structures are scattered freely all over the mucous membrane. If the stomach is to be regarded as a mesial organ, it follows that the small intestine which is a con- tinuation of it, is also a mesial organ, but this view affords no explanation of the stomach's projecting to the right lateral region, nor of the small intestine's describing a .large curve from the right side towards the middle line of the abdomen ; but if we assume that the stomach is fully developed towards the right side, the course both of the stomach and the intestine becomes at once perfectly clear, and the direction of this portion of the alimentary canal from the right aide to a median position is further explained i by its course being directed to join the large intestine, which we regard as a mesial and symmetrical organ. This view of the nature of the small intestine is further confirmed by the circumstance that this portion of the digestive canal, instead of being supplied by an artery from each side of the body, as is the case in azygos organs generally, is supplied by one vessel*, the superior mesen- teric, which arises from the side of the aorta a little below the coeliac axis. The stomach and bowels of chelonia are nearly as much laterally displaced as in the human subject. In the other reptiles they are not much out of the median line, yet in none are they exactly mesial, except towards the termina- tion. The cardiac end of the stomach tends, though often but a little, towards the left, but the pyloric is free, and can be brought without much violence to the middle line, but yet it is always found leaning to the right. The large intestine in man describes the greater part of a circle. The explanation of its various turns before it finally dips into the pelvis to gain the middle line of the sacrum has been given above. It differs from the small intestine both in its outward form and in its internal structure, and the opening leading from the ileum into 22 THE NATUEB OF THE SPLEEN. the large intestine is guarded by a valve. The ceecum, which is double in many animals, is the widest part of the large intestine. The symmetrical and mesial character of the large intestine is borne out by the arrangements of arterial supply ; for instead of having one vessel, the cfficum, and ascending and transverse colon, receive their vessels from the right side of the superior mesenteric artery, and the descending colon and sigmoid flexure and rectum from the inferior mesenteric. Tim Intestinal Canal in the VeHebrata. — The intestinal canal in all mammalia is marked ofi' from the stomach by a pyloric valve. Except in cetacea and a few edentata and cheiroptera, the division into a small and large intestine . prevails throughout. At the junction of the small with the large intestine a more or less perfect ileo-csecal valve is found, except in the monotremata, cetacea, and certain edentata and cheiroptera. A csecum nearly always exists. It is absent in all insectivora, in cheiroptera, in some of the edentata, and in certain cetacea. In the carnivora it is short and narrow ; absent in bears and weasles, present in quadrumana. In all ruminants it is capacious ; larger in solipeds ; in the horse three times as large as the stomach, being two feet long ; in the pachyderms somewhat smaller. In the hyrax there are two cseca ; in rodents it is absent ; in the dormouse short and small ; in the rat of great size ; in rabbit and hare eight times as capacious as the stomach. In carnivorous cetacea there is no csecum, but in balena a small one ; in herbivorous species sometimes a very large one, sometimes short and bifid ; in carnivorous marsupials there is no csecum, in insectivorous marsupials a SD(iall one ; in the frugivorous it is wide, twice as long as the body, and in the herbivorous species three times as long. In monotremata there is a small caecum. In Birds. — A pyloric valve usually exists in birds. The intestine of birds is shorter than that of mammalia, but longer, relatively to that of the body, than that of reptilia. The duodenum always forms a large loop, embracing the pancreas ; the re- maining portion is variously folded in different birds, the convolutions being spiral, concentric, or irregular. The distinction between the small and the large intestine now becomes less marked, there being no ileo-csecal valve, and villi being found on the mucous membrane of both ; this THE NATURE OF THE SPLEEN. 23 place of junction is, however, frequently indicated by the presence of a csecum, or rather of two cseca, for this diver- ticulum is most commonly double. The cseca are wanting in some vultures ; m the cormorant, -wryneck, and toucan, and in many carnivorous, insectivorous, and frugivorous birds. They are small and short in other vultures, in the eagles, and solan goose, and also when they exist in the insessorial tribes; they are longer in the nocturnal than in the diurnal birds of prey. Among the rasores, they are short in pigeons, but very long in the grouse, each measuring three feet, or thrice the length of the body. lu other rasores they are of moderate length. In the cursorial birds the intestinal canal approaches more nearly the mammalian character. The caeca, however, are absent in the cassowary, whilst in the ostrich they are wide, about two feet long, and have an internal spiral fold, like that of the hare. The large intestine beyond the caeca is large and mammalia-like in the ostrich, but usually is relatively short, straight, and not very wide. It terminates by an imperfect valved circular opening in the dUated cavity called the cloaca, into which also the ureters and the ducts of the reproductive organs open. In Reptiles. — The pyloric valve is usually present in reptiles, though not very distinct ; the intestine is shorter and wider than in birds. In saurians there is mostly an Ueo-cohc valve; the crocodile has no csecum. In the chelonians the intestine is long and muscular ; an ileo- caecal valve usually exists, and also frequently a csecum. In serpents the small intestine is elongated, the ileo-colic valve is indistinct, the large intestine sometimes has transverse folds in its interior analogous with the spiral valve in the same part in the cartilaginous fishes. The lower end of the larger intestine forms a cloaca, receiving the ducts of the urinary and reproductive organs. The presence of a csecum in certain ohelonia is associated with the use of a vegetable diet. In the more fish-like batra- chians the division into small and large intestine is imper- ceptible ; the latter ends in a cloaca. In Fishes. — The intestine is short and wide, and is distinguished into a large and small intestine by a slight constriction only ; there is no distinct ileo-colic valve, but sometimes a short caecum exists. The small intestine has usually connected 24 THE NATURE OP THE SPLEEN. with it, immediately below the pylorus, the appendices pyloricse ; the large intestine is often, as in sharks, pro- vided with internal folds, or a spiral valve. — (Marshall.) From the above considerations we conclude that the small intestine is a lateral imsymmetrical organ, that its left lateral homologue is undeveloped, and that the csecum and large intestine are mesial, bilateral, and symmetrical, and that the vermiform appendix is the only remaining vestige of the left small intestine. To recapitulate. We regard the stomach as a mesial organ, composed of a right and a left portion, the pyloric and the cardiac; that one is the lateral homologue of the other; that the left, or cardiac, instead of being developed, terminates in a cul-de-sac; that the right, or pyloric! portion, is developed, communicating with the small inr testine by means of the pylorus; that the small intestine is developed on the right side of the body only, and is unsymmetrical and lateral, and having passed from the right lateral region, it communicates with the large intes- tine in the middle line of the body ; that the left lateral homologue of the right small intestine is so far undeveloped that the only vestige found of it is the vermiform appen- dage; that the csecum and the large intestine are eacb double, or symmetrical organs, occupying the median line of the body ; in short, that the alimentary canal is sym- metrical from its commencement at the mouth down to the stomach ; that in the middle of its course, that is to say, from the stomach to the end of the small intestine, the symmetry is not carried out, but that from the csecum to the termination of the large intestine the alimentary canal is as symmetrical as it is at its commencement. A sketch of the development of the alimentary canal will elucidate this subject. The alimentary canal com- mences in the mucous layer of the blastoderm, in form of a groove, which is soon changed into a tube at each end, but is left open in the middle, upon the ventral aspect, and communicates by means of a tube, named the omphalo- enteric canal, or vitelline duct, with the vitelline sac ; this duot is soon obliterated, and the vitelline sac becomes the umbilical vesicle, which is henceforth connected with the embryo only by a slender elongated pedicle, containing the omphalo -mesenteric vessels, and is finally atrophied.' THE NATURE OF THE SPLEEN. 25 The alimentary canal itself is at first a straight tube closed at each end, and placed along the front of the vertebral column, to which it is closely attached above and below (supposing the embryo to be placed in an erect position), whilst in the middle of its course it is connected by a median membraneous fold, or rudimentary mesentery. Soon, however, it advances from the spine and forms a simple bend in the middle of the body, with a straight portion at its upper and lower end. The middle, or apex of the bend, advances to the umbilicus, where it is con- nected with the umbilical vesicle by the pedicle, and also by the omphalo-mesenterio vessels, which pass out there to the vesicle. By the early appearance of a slight dilatation which forms the future stomach, the primitive simple tube is divided into an upper and a lower portion, a. From the upper portion, besides the oesophagus which is formed by a gradual elongation of the part, there are ultimately developed the mouth, tongue, and salivary glands, the pharynx, larynx, trachea, and lungs. At first the upper end is closed ; at length a wide aperture appears which is not the mouth properly so called, but an opening upon which the mouth and lips are subsequently developed as superadded parts, commencing after Ahe eighth or ninth week. 6. The dilated portion of the tube which forms the stomach turns over on its right side, so that the border which is connected to the vertebral column by the mem- braneous fold (or true mesogastrium), comes to be turned to the left, the position of the tube being vertical, like the stomach of some animals. By degrees it becomes Tnore dilated, .chiefly on what is now the left border, but subse- quently the great curvature, and assumes first an Mique, and finally a transverse position, carrying with it the mesogastrium, from which the great omentum is afterwards produced. The pylorus is seen at the third month, but is very slightly marked. Immediately below the stomach the duodenum is formed, and upon this part of the canal commence the rudiments of the liver and pancreas, both having protrusions of the mucous membrane growing into their blastemic mass. c. In the meantime the part below the stomach becomes the intestinal canal ; that portion of it which is suspended by a mesentery forming, besides the duodenimi, the j ej unum, the ileum, the caecum , and the colon, 26 THE NATURE OF THE SPLEEN. whilst the lower and attached part constitutes the rectum. The place of distinction between the small and large intestine, which is soon indicated by the protrusion of the caecum, is at a point just below the apex, or middle of the simple bend already mentioned. As the small intestine grows, the part below the duodenum forms a coil, which at first lies in the commencing umbilical cord, but retires again into the abdomen ; about the tenth week afterwards it continues to elongate, and its convolutions become more and more numerous. The diverticula, sometimes found projecting from the small intestine, are supposed to be developed from a persistent portion of the vitelline duct, which continues .to grow with the rest of the bowel ; the large intestine is, at first, less in calibre than the small. The caecum appears as a protrusion a little below the apex in the primitive intestinal tube, and, as well as the commencing colon, is at first lodged in the umbilicus with the coil of the small intestine ; the appendix is at first of equal width. The ileo-caecal valve appears at the com- mencement of the third month, when the coils of intestine and caecum have retired from the umbilicus into the abdomen ; the colon is at first to the left of the convolu- tions of the small intestine, but then, together with the meso-colon, crosses over its upper part, at the junction of the duodenum and jejunum. The caecum and transverse colon are then found just below the liver; finally, the caecum descends to the right iliac fossa. At the fourth or fifth month the parts are in the same position as in the adult. The lower straight and attached portion of the tube eventually forms the rectum ; the anal orifice does not exist at first, but appears a week or so later than the oral opening. (Quain and Sharpey.) The. Liver. — We have just seen that upon the duodenum commence the rudiments of the liver and pancreas, both having protrusions of the mucous membrane growing into their blastemic mass. In the chick, the liver consists of a cluster of isolated follicles, not lodged in the walls of the intestine, as is the case in some of the invertebrata, but clustered round a sort of diverticulum of the intestinal tube, which is the first condition of the hepatic duct, and into which they discharge themselves. Its development has been traced in the bird from a conical protrusion of THE NATURE OF THE SPLEEN. 27 the intestinal canal, surrounded by a soft mass of blastema, in which, by a subsequent process of growth, the ducts are formed. In the mammalian embryo, it has been found to commence by a double mass of blastema attached to the outer wall of the intestinal tube, and having a conical protrusion of the internal membrane passing into each lobe of the mass. In the early foetus the right and left lobes of the liver are of equal, or nearly equal, size, and in consequence of the greater equality as to size between the two lobes, the position of the foetal liver in the abdo- men is more symmetrical as regards the middle line of the body. In the very early foetus it occupies nearly the whole abdominal cavity, and at a full period it still de- scends an inch and a half below the margin of the thorax; overlaps the spleen on the left side, and reaches down to the crest of the ilium on the right side. In the adult human subject it is situated in the upper part of the ab- dominal cavity, occupying the right hypochondriac region, and extending across the epigastric region into a part of the left hypochondrium. On the upper surface the line of attachment of a fold of peritonseum, named the broad or falciform ligament of the liver, marks off the surface unequally into a right and a left portion ; the right portion is much larger and more convex than the left. This liga- ment contains between its folds the round ligament which ascends from the umbilicus to enter the longitudinal fissure on the under surface of the liver. It is the remains of the umbilical vein of the foetus. The liver is composed of a large number of lobes ; five are enumerated in the human subject, but they are only apparent on the under surface. In some animals the whole surface is divided by a deep fissure into angular masses. In fact, anatomists have made the most of these lobes of the liver in their attempts to claim a symmetrical figure for this organ. Thus : " In the camivora and rodentia, which present the most complex form of liver that we meet with among mammalia, there are five distinct parts ; namely, a ' cen- tral', or principal lobe, and a right and left ' lateral' lobe, each with its ' lobular appendage.' The whole mass of the liver in man which we are accustomed to describe as consisting of a ' right' and ' left' lobe does in reality form but one (there being no real division between its two 28 THE NATUEB OF THE SPLEEN. portions), which must be regarded as the ' central' lobe-| the ' lobulus Spigelii' is the rudiment of the right ' lateral' lobe, and the ' lobulus caudatus' is its ' lobular appendage,' but the left ' lateral' lobe, with its lobular appendage,' is altogether undeveloped." There is only one hilum to the liver, which is transverse ; and, as a rule, the gall-bladder is a simple organ. The liver is supplied by one artery — the hepatic — and not by one from each side of the body. The large size of this organ, and the peculiarities of its circulation, etc., will demand our attention at a later stage. We will now trace the liver in the vertebrate series. " Among the vertebrata the liver, proportionately to the body, becomes progressively larger ; in passing from the mammal to the fish its general form corresponds with that of the abdominal cavity. Thus, it is broad in the apes and in the carnivora ; longer in the larger ruminants and long-bodied animals ; of moderate length in birds ; broader in the comparatively short chelonia and sauria, but long in the elongated ophidia ; broad and short in the frogs and toads, but long in the newts, stretching widely into the abdomen of the broad-shaped skates and rays, but lengthened out in the eel. Its position is usually somewhat mesial, but in the mammalia with large com- pressed stomachs it is placed more towards the right side, as is also the case in the anthropoid apes. In fishes it generally lies more on the left side of the body. In birds in which the diaphragm is complete, the liver is notched for the reception of the heart and pericardium. In reptiles, amphibia, and fishes which have no diaphragm, the liver, also reaches up to the pericardium, except when the body is very long, as in the serpents and eels. The liver in the mammalia generally is very simple, its lobes being only slightly marked. In the ruminants it is sub- divided into three lobes; in the rodentia and carnivora there are from three to five lobes ; in the llama, amongst ruminants, the under surface — and in the capromys, a rodent animal, the whole surface — is divided by a deep fissure into angular masses, resembling those of the kidney of the bear. In birds the lobes are two, and of equal size ; in reptiles and amphibia the lobes are generally two, but the liver is undivided in the ophidia ; in fishes the liver is often more subdivided. The microscopic structure THE NATURE OF THE SPLEEN. 29 of this gland in all the vertebrata resembles that of the human liver. In mammalia a gall-bladder is sometimes present and sometimes absent amongst the herbivorous kinds ; it is present in nearly all ruminants, as in oxen, sheep, goats, and antelopes, but not in the camels and stags. It is also present in solipeds and in most pachydermata, as in the horse and tapir, peccary, and elephant, but not in the pig. In the elephant the hepatic duct is dilated and thickened, and has a spiral fold within. The gall-bladder is wanting in mice and. hamsters amongst rodentia, also in the sloths amongst the edentata, and in true cetacea. In the carnivorous and insectivorous kinds the gall-bladder is present. In the cat and a few other animals it is some- times found double, and there are sometimes three. When the gall-bladder is present, a cystic, hepatic, and common bile-duct exist. In birds the gall-bladder is generally pre- sent, but is -wanting in certain species of a particular genus without obvious relation to the habits or food. It is absent in the ostrich, pigectas, toucans, and many par- rots. Proceeding from the liver in birds are two ducts — one hepatic to the duodenum, the other to the gall-bladder — ^from which a cystic duct runs on to the duodenum ; there is, therefore, no common bile-duct : when the gall- bladder is wanting, the two hepatic ducts open separately into the intestine. In reptiles a gaU-bladder always exists, but it varies in form. It is placed at a distance from the liver, and has a long cystic duct in the ophidians, but it is imbedded in the substance of that gland. In the chelonians there is either a common bile duct, or the cystic duct and hepatic duct open separately into the duodenum. The gall-bladder invariably exists in amphibia. In fishes this receptacle is usually present, though it is absent in many genera, being then replaced by a dilatation upon one of the hepatic ducts, which are here usually numerous. The Blood-vessels of the Liver. — In all the vertebrata the -liver receives blood both from the hepatic artery and the portal vein. In the mammalia this vein, as in man, has only a few communications with the lumbar and pelvic systemic veins. In birds and reptiles the communications between the pelvic and portal vein is such that a part of the blood from the lower extremities and from the tail joins the portal blood, and passes into the liver. In fishes 30 THE NATUKB OF THE SPLEEN. the caudal veins, and sometimes those from the reproducr tive organs and the air-bladder, are connected with the portal system." (Marshall). From the above it must be apparent that although the liver may be composed of almost any number of lobes, aggregated together, and may vary in shape and have any number of ducts, yet in no case are there two livers, two gall-bladders, two hepatic arteries, and two portal systems, either united or otherwise, in the median line of the body. There is reason to conclude that the biliary apparatus of the left side of the body is undeveloped; and since the biliary apparatus is developed in connection with the small intestine, the absence of that organ on the left side of the body confirms the hypotheses of the absence of the left small intestine. These views receive remarkable con- firmation from a review of the portal and umbilical circu- lation, and their anomalies are immediately explained. If, for the sake of argument, we suppose that the liver is a median and symmetrical organ, composed of a right and a left liver, conjoined in the mesial line of the body, ther^ ought, then, to be two portal veins — one collecting the blood for the ohylopoietic viscera of the right side of the alimentary canal and its appendages, and the other on the left side collecting its blood from the ohylopoietic viscera of the left side of the alimentary canal, and these vessels ought to be symmetrical in size and position, etc. Now, what we actually do find is quite a different state of things. The superior mesenteric vein on the right side of the body collects and returns the blood from the small intestine, and from one-half of the large intestine, namely, from the ascending and transverse colon. The trunk formed by the union of its several branches inclines upwards, and on the right side passes into the liver as the portal vein. Now, on the left side of the body the difference is very striking. The inferior mesenteric vein commences at the rectum by branches, which unite with those from the remaining por- tion of the large intestine, namely, the descending colon, and passes upwards on the left side of the body, terminating by falling into a large vessel which has been inappropriately called the splenic vein, and which collects the blood from^ the great end of the stomach and the spleen. This large union vein is directed from left to THE NATURE OP THE SPLEEN. 31 right, imbedded in the substance of the pancreas, crosses over the front of the spine to the other side of the body, and terminates by joining the superior mesenteric vein, which, as we have mentioned above, passes into the liver as the portal vein. The absence of both the biliary ap- paratus and the small intestine on the left side of the body completely explains the anomalou,s absence of sym- metrical arrangement. A notable exception to the law of symmetry in connection with the foetal circulation cannot be satisfactorily eluci- dated on the supposition that the liver is a symmetrical organ, composed of a right and left liver, united in the median line ; but receives a ready solution if we regard the liver as a-symmetrical. It will be remembered that there is but one umbilical vein to carry the placental blood to the liver, whUst there are two umbilical arteries. An explanation is afforded by the fact that there are not two livers ; for, as there is but one liver, there is but one umbilical vein. The umbilical arteries are two and have nothing to do with the liver, being the continuations of the common iliac arteries, into which the aorta divides. The Pancreas, as is the case with the liver, is developed in connection with the small intestine; it commences in the form of a small bud from the left side of the intestinal tube, having a protrusion of the mucous membrane grow- ing into its blastemic mass. In the adult it is embraced by the curvature of the duodenum, and extends across the epigastric into both hypochondriac regions. Its inti- mate structure closely resembles that of the salivary glands. The pancreatic duct sometimes opens into the intestine by a common oriiice with the common bile-duct, and sometimes separately. The number of ducts is un- certain — one, two, or three — and like the salivary glands, the pancreas receives its blood-vessels at aU points and from various sources — the hepatic, splenic, and superior mesenteric — and its blood is returned by the splenic and superior mesenteric veins. " The pancreas is present only in the vertebrata and the higher moUusca; it is not so widely distributed amongst animals as the liver, and it assumes a rudimentary form in fishes. In mammalia, birds, and reptiles, the pancreas occu- pies the concavity of tl^g constantly present curvature of the 32 THE NATURE OE THE SPLEEN. duodenum. In mammalia, when the duodenal mesentery is short or absent, as in the quadrumana, camivora, rumi- nants and solipeds, the pancreas is compact and elongated, with a portion extending towards the spleen, so that it may seem bilobed, as in the camivora and ruminantia, or even trilobed, as in the horse, the splenic portion being double ; when, however, the duodenum has a wide mesen- tery, as in rodentia, the pancreas forms an arborescent mass between two layers of the mesentery, as seen in the rabbit and rat. The typical number of ducts in the mam- malia appears to be two, as indeed is the case in the early condition in man, the upper and larger duct alone persist- ing. In the horse and dog there are also two ducts, the lower one being the larger in the dog ; the latter opens separately into the duodenum by a common orifice. In the rabbit, the upper duct is very minute, and the chief duct opens from nine to twelve inches below the pylorus. In all cases the pancreatic fluid is discharged into the duodenum. In certain camivora, as in the seal, and some- times in the cat, the chief duct dilates into a reservoir • previously to entering the intestine. In hirds, the pancreas is proportionally larger than in other vertebrata ; it usually consists of from two to six elongated portions, attached as usual to the much bent duodenum. Each portion of the gland has a duct gene' rally opening separately into the intestine. There are six ducts in the vulture, fowl, heron, and grebe ; three in the crow, pigeon, grouse, and duck ; but only one in the eagle, ostrich, and stork. In the stork alone, the single pan- creatic duct opens by a common orifice, with a single hepatic duct. Usually one at least of the pancreatic ducts in birds opens above the bile duct, but this is not constant ; when several ducts exist, they usually open alternately with other hepatic or cystic ducts ; the cystic duct generally opens lowest. In the ostrich, the bile escapes through the single hepatic duct close to the py- lorus, and the pancreatic juice also by a single duct three feet lower down. In reptiles, the pancreas is usually large. It is larger in the herbivorous than in the carnivorous saurians, being largest in the iguanas. In the chelonians, the gland is even ramified as in the rodents. In the ophidians, it is either long and bifid, pyramidal, of round. The duct is tp:e nature of the spleen, 33 nearly always single, and enters the duodenum separately but sometimes with the bile duct. In the serpents, the pancreas is joined to the spleen, and has even been con- founded with it. In the amphibia, the pancreas is found in the mesentery, between the stomach and the duodenum. In the lowest amphibia, as in the siren, the pancreas is much subdivided, so as to approximate to the form of the pyloric appendages in the fishes. Its ducts form numerous parallel canals, opening separately into the duodenum. In fishes, the pancreas is a small gland sometimes found attached to the liver. The trout possesses this organ as well as the pyloric appendages." (Marshall.) From this description it will be seen that the pancreas is composed of an indefinite multiplication of lobes, com- municating with numerous ducts, opening separately or in conjunction with the common bile duct into the small intestine ; that there is no appearance of symmetry in its construction, and that it has not two arteries direct from the aorta specially devoted to it. The Absorbent Si/stem.— The want of symmetry existing on the opposite sides of the abdominal cavity is further evidenced by a brief consideration of the absorbent system. The thoracic duct is a mesial organ, not, however, always a single trunk throughout its whole extent, for it fre- quently divides opposite the seventh or eighth dorsal vertebra into two trunks, which soon join again. It has indeed been found by Uruikshank double in its entire length. The thoracic duct is the common trunk. The lacteals which commence in the coats of the intestine extend to the thoracic duct in which they all terminate ; they are derived in far larger numbers from the small than from the large intestine. Having passed throiigh the lymphatic glands the lacteals gradiaally unite as they approach the attached border of the mesentery, two or three perhaps joining to form one ; and so they become diminished in number, until at length, near the root of the superior mesenteric artery, only two or three trunks remain, which end in the thoracic duct. In this way the lacteals from the whole of the small intestine, from the ciBcum and from the ascending and transverse parts of the colon, terminate. But the trunk from the left side of the body, instead of receiving its share of branches from 34 THE NATURE OF THE SPLEEN. the small intestine and being of equal size and importance ■with that on the right side, is a small trunk, which having received branches from the descending colon, and its sigmoid flexure, turns upwards and opens by a separate trunk into the lower end of the thoracic duct. The small size of this trunk, and the fact of its receiving so few branches, and these from the left side of the large intestine, are explained by the absence of the small intestine on the left side of the abdominal cavity. DIAGEAM TO ILIitTSTRATE THE STMlIETEIOAIi ABBANQEMENT OF THE ABDOmiNAIi YISCEBA. i. The Stomach. B. The Small Intestine, c. The Large Intestine, v. The ■Vermiform Appendix. L. The Liver, s. The Spleen, p. Tbe Pancreas. The shaded portion represents those parts of (he al)dominalTiscexa which are un- developed on the left side of the body. Having given a slight sketch of those portions of the alimentary canal and their appendages, which occupy the right side of the abdominal cavity, we now pass on to the THE NATURE OF THE SPLEEN. 35 consideration of their lateral homologues, which are situated on the left side of the body. We may enumerate these as the following — the cardiac stomach, only partially developed ; the vermiform appendix, the only remnant of the small intestine ; the left half of the csecum and of the large intestine, and finally the spleen. We have described above the condition of the stomach in the vertebrate series. It is only necessary to add here, that pain in the left side of the stomach is frequently referred to the left side of the head, and that pain in the right side is referred to the right side of the head ; and that during the progress of the digestive process in souie animals, a constriction is observed partially dividing the right from the left stomach ; and there are certain other pathological conditions which elucidate this subject. In man the great cul-de-sac of the stomach projects beyond the oesophagus to the left for about two or three inches, and all the structures entering into its formation bear evidence of an arrest of development, whilst in the lower animals this part of the stomach is not only to some extent distinct from the pyloric stomach, but is completely different in structure, and, failing its due physiological function, it is appropriated to other purposes. The pylorus on the right side never has a left lateral homologue in a valvular orifice, viz., a left pylorus. The representative of the right small intestine is the Vermiform appendix. Proceeding from the inner and back part of the cajcum, at its lower end, is a narrow, round, and tapering portion of intestine, named appendix vermiformis.. This process is usually about the width of a long quiU, and varies from three to six inches in length, differing much in its dimensions in different cases. Its general direction is upwards and inwards behind the caecum, and after describing a few slight turns it ends in a blind point. It is retained in its position by a small fold of peritonseum, which forms a mesentery for it ; this csecal appendix is hollow down to the extremity, and its cavity communicates with that of the caecum by a small orifice, sometimes guarded by a fold of mucous membrane. Its coats are the same as those of the csecum, but the longitudinal muscular fibres, which are continuous with those of the three bands upon the caecum and colon, form a uniform 36 THE NATURE OP THE SPLEEN. layer round the appendix just as in the small intestine. The vermiform appendix is developed from the Cfficum, A distinct appendix exists in man, in the ourang-ontang, and in the wombat, but apparently in no other animal. As is well known, the vermiform appendix is usually con- sidered to be. a part of the caacum arrested in its growth, and is usually regarded as the rudiment of the long caecum found in mammalia. But there are strong reasons for looking upon it as the representative of the undeveloped small intestine of the left side of the body; the left lateral homologue of the right small intestine ; and the character of its mucous membrane is not an insuperable objection to this view. We must refer to what we have said above about the large intestine aud its condition in the vertebrate series for the evidence in favour of its double nature, and the frequent occurrence of two cseca will explain its true state in man. The only remaining organ is the spleen. There are two opinions held with regard to the Spleen. One opinion is, that it is the left lateral homologue of the liver, and is situated on the left side of the body ; and the . other opinion is, that it is a mesial or azygos organ, occupy- ing the median line of the body, and having no lateral homo- logous relationship to the liver. Miiller, as we have seen above, advocates the second opinion in the following words : " In man aud mammalia the spleen lies in the fold of peritonaeum, which is continuous with the serous covering of the anterior and posterior surface of the -stomach, and extends between the great curvature of the stomach, the diaphragm, and the transverse colon ; and which at the part where it connects the stomach to the transverse colon is called the great omentum. This portion of peritonseum passes originally from the spinal column in the middle line to the great curvatttre of the stomach, forming a meso-gastrium in which the spleen was developed. The spleen, therefore, is not an organ proper to the left side of the body of which the fellow of the opposite side is wanting." Miiller omits to state that several other organs are also contained in the same fold of peritonseum which cannot all be regarded as median organs, namely, the pancreas, close to which the spleen is developed, and the duodenum. Moreover, due allowance THE NATURE OF THE SPLEEN. 37 has not been made for the arrest of development of the great cul-de-sac of the stomach, and for the absence of the small intestine on the left side of the body ; nor can the dispositions of the folds of the peritonseum be regarded as a guide in a question of symmetry. Again he says, " The spleen should be regarded as an organ originally situated in the middle line, just like the liver, which at first, when its two lobes were equal, did not belong to the right side more than to the left," and " Doellinger supposes the spleen to be formed merely for the sake of symmetry, to be the fellow of the liver ; the rudimentary liver as it were, of the left side. But the liver is originally symme- trical" — consequently the presence of the spleen is not required to complete the idea of symmetry. Here again Miiller has derived his inference from circumstances which are not conclusive. The number of the lobes of the liver is a matter of uncertainty. Almost any number of lobes may be aggregated together, and has nothing to do with the question of symmetry; and if, as there is reason to believe, the small intestine itself is a lateral organ, the liver which is developed in connection with it must be a lateral organ also. Miiller having proved to his satisfaction that the liver is a median organ on the ground that it is symmetrical in its form, would have increased the weight of his argument had he been able to add that the spleen also is symmetrical in form. This, however, he has been unable to do, as it presents no appear- ance of symmetry, and it is supplied by one arterial trunk instead of two. The difficulty with regard to the rela- tionship of the liver and spleen has not arisen so much from the apparent want of symmetry in the situation of the spleen with respect to the liver, but rather from its failing to exhibit any trace of the function which is per- formed by the liver ; and since the spleen has never been found CO secrete bile itself, the ancients endeavoured to overcome the difficulty by supposing that the spleen aided the Hver in that operation, and this view has, in modern times, received support from the observation that the splenic vein is one of the largest sources of supply to the portal system. Of this, however, more hereafter. The Spleen is situated in the left hypochondrium, at the pardiao end of the stomach, between that viscus and the 38 THE NATURE OP THE SPLEEX. diaphragm. It is a highly vascular and easily distensible organ, and has no excretory duct. It is unsymmetrical in form, and somewhat lobular ; the external free convex face of the spleen is smooth and covered by the perito- nseum, but the internal concave face is irregular, and presents a vertical fissure, named the hilum, which trans- mits the blood-vessels and nerves. The fissure is not always present. Two layers of peritonaeum reflected from the spleen, at the borders of the hilum, on the great cul- de-sac of the stomach, aiid containing between them the splenic vessels and nerves, and the vasa brevia, constitute the gastro-splenic omentum, which thus serves to attach the spleen to the cardiac end of the stomach. The tail of the pancreas touches the lower end of the inner surface of the spleen. To the diaphragm the spleen is attached by a reflection of the peritonaeum, named the suspensory ligament. The lower end is in contact with the left end of the arch of the colon, or with the transverse meso-colon. Its weight fluctuates usually between four and ten ounces. In intermittent fever it is much distended and enlarged, weighing as much as eighteen or twenty pounds. It is unnecessary here to describe the structure of the spleen. We must refer the reader to the works of Soem- mering, KoUiker, Krause, Gray, and W. Miiller. The splenic artery in man, the largest branch of the coeliac axis, is directed horizontally towards the left side, together with the splenic vein behind the iipper border of the pancreas, and divides near the spleen into several branches : some of these enter the fissure in this organ. The pancreatic branches supply the pancreas. The gastric branches, vasa brevia, enclosed within the gastro-splenic omentum, passing from left to right, reach the left ex- tremity of the stomach. The gastro-epiploic artery runs along the great curvature of the stomach. In some ani- mals the splenic artery is smaller than the other branches of the coeliac axis. In some birds the blood-vessels are derived from one of the branches of the gastric previous to its distribution to the stomach, liver, duodenum, and pancreas. The vasa brevia, when distended with blood, have been mistaken for ducts proceeding from the stomach to the spleen, and vice versa. The splenic vein is of very considerable size ; considerably larger than the splenic THE NATURE OF THE SPLEEN. 39 artery. It commences by five or six branches which issue separately from the fissure of the spleen, ,but soon join to form a single trunk It is directed from left to right, embedded in the substance of the pancreas. It is joined by the inferior mesenteric vein, when a large trunk is formed, which is inaptly also called the splenic vein. This trunk, which unites the venous system of the two sides of the body, and might be more appropriately named the union vein, crosses the front of the spine to the right side of the body, and falls into the superior mesenteric vein neai'ly at right angles. These two trunks form the portal vein. The splenic vein receives in its course veins from the neighbouring parts. When the circulation in the liver is obstructed, this union vein transmits the congestion across to the opposite side of the body directly to the spleen. " In the amphibia the large size of the spleen, and its peculiarly lax and distensile texture, are in perfect harmony with the requirements of the animals of this class, and it is peculiarly adapted as a reservoir for the blood, which accumulates in the portal system, inferior vena cava, and the hepatic reservoir, during the suspen- sion of the respiration." (Gray.) It has been mentioned that the splenic vein is the largest of the constituent channels of the portal system, and probably the above remarks afford some explanation of this fact. If we regard the spleen as an organ proper to the left side of the body, the course of the blood in the splenic vein to the opposite side of the body, namely, to the liver, is altogether anomalous, and is the only instance of the kind in the body. But if we regard the biliary apparatus and portal system as absent on the left side, the explanation is at once evident, and affords another argument in sup- port of our view of the subject. There is a similarity in the course of the blood conveyed by the splenic artery and hepatic artery ; for the blood from the splenic artery having passed ^through the spleen, is conveyed to the portal vein, and the blood of the hepatic artery is also believed to be conveyed into the portal system before gaining the hepatic veins and vena cava. The Spleen appears in the foetus about the seventh or eighth week, on the left side of the dilated part of the ali- mentary tube or stomach, and close to the rudiment of the 40 THE NATURE OF THE SPLEEN. pancreas, at its distal end, but perfectly separate from ttis body. This distinct separation of the spleen and pancreas is most evident at this period, for a distinct granular mem- brane divides them, whilst also the dark granular traces of the pancreatic mass, and the lighter colour of the rudi- mentary spleen, make this distinction more manifest. The spleen does not, as Arnold states, arise like the pancreas from, the duodenum, and exist at first as a common mass with that gland. (Gray.) By the tenth week the spleen forms a distinct lobulated body, placed at the great end of the stomach. After birth it increases rapidly in size, and in comparison with the weight of the body, it is as heavy a few weeks after birth as in the adult. This organ is peculiar to vertebrate animals. Separate splenculi, which are sometimes found in the human subject,* bring to mind the multiple con- dition of the spleen in some animals, and also the notching, often deep, of the anterior margin of this organ in man. The spleen exists, without exception, in all the vertebrate animals. It varies much in shape even in mammalia; being, in different cases, round, oval, much elongated, lobulated, and even multiple. The latter condition is seen in the dolphin. It is largest in the bats, and smallest in the cetacea. The spleen presents its maximum of development in mammalia in connection with the greater general completeness and requirements of their organiza- tioUf In the amphibia it is peculiarly lax and distensible. In birds the spleen is generally small as compared with the body ; much smaller than in mammalia ; its shape is either round, oval, fusiform, or flat. In reptiles it is of variable size, and differs in form according to' the general shape of the body. As we descend in the scale of the verte- brate series, the function of the spleen appears to be con- siderably reduced in importance, as shown by the extreme diminution in its size ; a diminution more marked in some of the orders of this class than in any other of the vertebrata. In fishes the spleen is universally present, but its small size in proportion to the body shows that it is an organ of less functional importance than in the mammalia. In birds and reptiles this organ is usually attached to the pancreas. In reptiles and fishes it is rather connected with the intestine than with the stomach, as in the mammalia. THE NATURE OF THE SPLEEN. 41 To recapitulate. We have seen that two theories have been entertained with regard to the spleen. In one, both .the liver and the spleen are regarded as mesial organs, and the spleen is looked upon as a blood-gland, having nothing to do with the liver. In the other, the liver and spleen are both held to be lateral organs, symmetrical with each other, and the spleen as an undeveloped liver of the left side, and aiding the liver in its biliary function. The only argument in favour of the spleen's being a mesial organ is derived from the situation of its development. There can be no doubt that in the bird the spleen is developed in the meso-gastrium ; that is, between layers of peritonaeum, which originally pass from the spinal co- lumn in the middle line, to the great curvature of the stomach. This appears, in modern times, to have settled the question as to the mesial nature of the spleen, but upon a careful inquiry this is found to be capable of explanation; for that portion of the peritonaeum which should correspond on the left side of the body with that fold of peritonaeum which on the right side is associated with the pylorus and duodenum, is altogether absent, on account of the iindeveloped state of these parts on the left side of the abdomen. Moreover, the peritonseum cannot be considered a satisfactory guide, for it is itself unsym- metrical, and the various organs are outside it, and it envelopes in the same folds parts which are most dissimi- lar in their nature. It will be also borne in mind that the spleen originates close to the pancreas, which cannot be supposed to be a symmetrical organ. The situation of the spleen, in close proximity to the pancreas and the small intestine, is in perfect accordance with the idea of its homologous relationship with the liver, which is really connected with those parts rather than with the stomach to which it is attached by peritonaeum. Again, the liver has been supposed to be itself symme- trical and mesial, and consequently no organ is required to fulfil the idea of symmetry; but an examination of the liver in the vertebrate classes shows that the liver, although its lobular structure may give rise to that appearance, is never really a symmetrical organ, and a similar remark would apply to the spleen. Again, the hypothesis that the spleen assists in tlie 42 THE NATURE OF THK SPLBKN. function of the liver is usually regarded as untenable, because the blood of all the chylo-poief^ic viscera, and even that from the inferior extremities in the^ower vertebrata, enters the vena portae. Hence it is inferred that there is nothing peculiar in the fact of the splenic blood going to the liver. But the course of the splenic vein is most abnormal, and can only be sufficiently accounted for by the hypothesis of the absence of a special portal system on the left side of the body. The absence of bilateral symmetry in the liver, and also in the spleen; their symmetrical situation with re- spect to each other ; their being each supplied by a cor- responding trunk from the aorta, together with the want of symmetry in that portion of the abdominal viscera with which the liver is connected, all confirm the opinion which has been held, though vaguely, from the earliest times, that the spleen is symmetrical with the liver, and negative the modem idea that the spleen is a mesial organ. There is, however, another and greater difficulty, namely, what is the function of the spleen, and if it is anatomically symmetrical with the liver, how is it connected with this organ physiologically 1 The philosophers of antiquity, when regarding the spleen as symmetrical with the liver, endeavoured, by various suggestions, to connect them in function ; but since it was apparent that bile was not immediately secreted by the spleen, they concluded either that this organ was au undeveloped liver, or that it prepared the blood during its passage through its substance for the elaboration of bile in the liver, or that black bile was secreted by the spleen in the same way as the yellow bile was secreted by the liver ; but actual experiment has demonstrated that bile is secreted where the spleen has been removed, and the splenic blood, by going to the vena portae, does not differ in this respect from that from all the chylo-poietic viscera. The modem opinion, with regard to the spleen, is that it is unsymmetrical with the liver; that it is a blood- gland, having nothing to do with the function of the liver ; and that it produces certain changes in the properties of the blood as it passes through its tissues. The assigned function of this organ has of course changed in accordance THE KATUEB OF THE SPLEEN. 43 ■with these views, and the spleen is now believed by some persons to supply the germs of those cells, which are ultimately to become blood corpuscles, and for the follow- ing reasons : — 1. There is no difficulty in the admission of such cor- puscles into the smaller veins of the spleen. 2. There is an unusual proportion of colourless corpus- cles in the blood of the splenic vein. 3. The period of gi-eatest functional activity of the gland generally is during the state of early childhood, when the formative processes are going on with extra- ordinary activity, and there is at the time a larger propor- tion of colourless corpuscles in the blood than at any subsequent period. 4. The state of blood when there is a multiplication of its colourless corpuscle^ is almost always associated with hypertrophy of this body. It must be admitted the above reasons are not very powerful. The hypothesis is most conclusively answered by Professor Owen. " The splenic artery," he remarks, " must pour more blood into the splenic reservoir than is needed for the mere nutrition of the organ, aud consequently the blood must there undergo change. But the spleen receives too small a portion of the circulating mass to have any defi- nite ibflueuce on the manufacture, or general condition, of the blood. Such changes as are effected in the splenic locality more probably relate to the function of the gland to which the altered blood is exclusively carried, and it is to be noted that the splenic vein is the largest of the constituent channels' of the portal one. With reference to the hypothesis of sanguification, it may be remarked that in no mammalian order is the mass of blood so great, or so full of blood discs, as in the cetacea ; yet in them the spleen has its relative least size." The fact that the spleen is remarkably small in the foetus, and excessively large during the prevalence of cer- tain fevers, the result of blood poisoning, is favourable to the view that at least one of the alterations effected in the blood has reference to the removal of some of the effete constituents of the circulation ; the decomposed elements passing from the spleen, by the splenic vein, to be eUminated by the liver from the system. Nor is it 44 THE NATURE OF THE SPLEEN. necessary to suppose, as we shall see hereafter, that the formation of the bile is solely dependent upon this supply. It may be objected to the theory that, the blood, either by its retarded motion through the serpentine splenic vessels, or by its stagnation in the splenic cells, or by changes wrought in it by some action of the spleen, is rendered fit for the secretion of bile in the liver ; and to the theory that, the splenic blood is loaded with properties which the action of the liver separates from it ; that we do not usually meet with such arrangements as these in the animal economy — indeed, no instance could be ad- duced of a like nature — one organ elaborating properties in the blood that they may be removed by another ; or a part producing changes in the blood fitting it for the secre- tion which is to be performed by another. The tissue of each gland has the power of extracting its peculiar secre- tion from the common mass, further, bile is secreted when the spleen has been removed, and it is secreted in those cases in which the vena portse empties its blood directly into the inferior cava. Moreover, it has been as- certained that bile is produced in the liver from the blood distributed to its substance by the portal vein and the hepatic artery, and not from either of these vessels excla- sively, and that the bile may continue to be secreted even if either of these vessels be obliterated, provided the sup- ply of blood be sufficient. The anatomical details we, have given above afford at once a clue to the solution of this difficulty. We have shown that the spleen has no biliary apparatus associated with it. We have also pointed out that the course of the splenic blood is across the mesial line of the body, and falls into the portal system of the liver, an organ proper to the opposite side of the abdomen, this course being al- together exceptional and different from what occurs in the case of any other viscus. Now, since the spleen is unpro- vided with a biliary apparatus of its own, and it makes use, so to speak, of the biliary apparatus of the liver, an organ on the opposite side of the body ; and since, as we have shown, the liver is symmetrical with the spleen, and all symmetrical organs are similar, we are led to conjecture that the liver is composed of an organ similar to the spleen, , combined with a biliary apparatus. \ We pass on, then, to the consideration of the question THE NATURE OP THE SPLEEN. 45 whether the liver may not in reality be regarded as a combination of two organs; viz., a blood-gland; similar to the spleen, and a biliary apparatus confibined together. Ruysoh appears to have been one of the first anatomists who classified the liver with the thyroid, supra-reual cap- sules, and lymphatic glands as a vascular or blood-gland — ' glandula sanguinea. ' " The action of the ductless glands — that of extracting material from the blood elaborating it, and, instead of eliminating it by ducts, returning it into the blood by means of a venous or lymphatic absorp- tion is no doubt, to a certain extent, imitated by the liver, the largest secreting gland in the body; for in the embryo the liver is indeed a true blood-gland." (Carpenter and Power). Without laying much stress here upon the compara- tive size of this gland, which is by far the most bulky of the abdominal viscera, we shall pass on to consider its anatomical and physiological characteristics so far as they elucidate our subject ; and the first thing which attracts attention when considering the liver is its double vascular supply, and this alone is sufficient to lead to the conjec- ture that it is compound in its nature, for it differs in this respect from all the other abdominal viscera. It will be remembered that the hepatic artery, the branch of the coeliac axis which corresponds with the splenic, is distributed to the proper coat of the liver, to the coats of the various ducts and vessels, and to the capsule of Glisson, and forms plexuses upon the elaborate inter- lobular cellular structure ; and that it probably terminates in the portal vein by the intervention of a capillary net- work ; and that, in addition to this, the portal vein is dis- tributed to the hepatic lobules after the manner of an artery ; and that it is the portal vein which, under ordi- nary circumstances, is the main source of the biliary sup- ply. It may, however, here be suggested that this is not conclusive; for there is another organ in the body, namely, the lung, which also has an arterial and a venous circula- tion, the venous circulation being distributed after the manner of an arterial.- Now, the objection, may be an- swered, and be made to give additional weight to the theory of the compound nature of tlie liver, by considering the nature of the lung, and tracing its progressive development in the animal series. The bronchial vessels which supply 46 THE NATURE OF THE SPLEEN. the cellular tissue of the lung, forming plexuses in the ins terlobular cellular tissue, and spreading out upon the surface of the lung beneath the pleura, may be compared with the hepatic arteries, and the pulmonary vessels which convey the blood sent through the lung by the heart for aeration may be compared with the portal vein. Without going at great length into the comparative anatomy of the lung, we may note that in fishes the air- bladder formed by a prolongation of the internal tegumen- tary membrane constitutes a rudimentary lung, and exists at the same time that the lung -function is being performed by the gills. The air-bladder is, in fact, acknowledged to be an accessory respiratory organ. In some fishes the resem- blance of the air-bladder to a lung is very decided, and its connection with the function of respiration is evidentlymost important. The canal by which it communicates with the alimentary canal opens, in some instances, at the back of the mouth ; so that a gradual approach is seen to the ar- rangement which exists in air-breathing animals. In these fishes, as in the amphibia that retain their gills, it would appear that the respiration is accomplished partly by the lungs, and partly by the gills. There can be no doubt that the lung may be regarded as a combination of the air-blad- der and the gUls, and that however perfectly the union is accomplished, it is in reality a combination of two dis- tinct organs, and there are not indeed wanting indications in the mammalian lung of the combined function of the two organs of which it was originally composed. With regard to the liver, the evidence is more conclusive ; for the function of each portion can be readily detected, not- withstanding that, as in the case of the lung, the structural union is complete. From time to time, various attempts have been made to separate, anatomically, the substance of the liver into two distinct portions, and this in consequence of two dis- tinct functions of the liver having been recognized by many physiologists. Ferrein went so far as to describe the medullary sub- stance as being red in colour and of a pulpy consistence, and the cortical as friable in its structure and of a yellow- ish red colour; and MiiUer distinctly admits a kind of double substance, although he objects to its designation, medullary and cortical. In his physiology, however he THE NATURE OF THE SPLEEN. 47 is disposed, to modify his previous idea of two substances, for he says : " From my researches, however, it results that there is but one kind of real hepatic substance formed of agglomerated bihary canals, but the ramified divisions of this substance being connected by a vascular cellular tissue which is often of a dark colour, a contrast between this and the yellow substance of the acini is produced." A similar relation of the constituent parts of the liver exists in the embryo of the bird in the yellowish twig-like ramifications of the biliary canals, as seen on the surface of the organ rising out of a reddish vascular tissue. Robin goes yet further : he recognizes two distinct parts in the liver — a biliary organ and a glycogenic organ. He regards the lobules with the liver-cells and blood-vessels as the parts concerned in the glycogenic function of the liver, and the little glands which open into the biliary ducts all along their course, and are arranged on the duct in the form of fronds of a fern, as the biliary organ. It is only necessary to say in answer, that there is no direct evidence that the racemose glands (vestiges of Malpighian bodies T) attached to the excretory biliary passages (?) have anything to do with the secretion of the essential constitu- ents of the bile ; and, as they are not even found in some animals that produce a considerable quantity of bile, we may regard the fact of the isolation of two organs in the liver — one for the secretion of bile, and the other for the production of sugar, as still unsettled. (Flint.) What we are in quest of is a fibro-cellular structure, supporting a close arterial and venous plexus, similar to that found in the spleen ; and pathology points out this more distinctly. For in cirrhosis of the liver, when there is undoubtedly a partial atrophy of the biliary secreting portion of the liver with hypertrophy of the cellular sub- stance, the distinction is very evident. But as we.see in the case of the lung, organs combined together by nature cannot easUy be separated by art. It is worthy of remark, that in the mammalian embryo (the dog) the liver has been found by Bischoff to com- mence by a double mass of blastema attached to the outer wall of the intestinal tube immediately beneath the dilatation for the stomach. It was formerly supposed that the chief and only 48 THE NATUBB OF THE SPLEEN. important office of the liver was to produce bile, and all physiolcjgical researches into the function of this organ were then directed to thfe question of the uses of the biliary secretion; but in 1848 it was announced by Bernard that he had discovered in the liver a new and important func- tion ; and he proceeded to show, by an ingeniously con- ceived series of experiments, that the liver is constantly producing sugar of the variety that had long been recognized in the urine of persons suffering from diabetes mellitus. The great physiological and pathological impor- tance of the discovery, attested as it was by experiments which seemed to be positively conclusive in their results, excited the most profound scientitic interest. In 1857 Bernard discovered a sugar-forming material in the liver analogous in its composition and properties to starch ; and this seemed to complete the history of glyco- genesis. Shortly after the publication of the glycogenic theory, it was found that other changes were effected in the blood in its passage through the liver, and, physiolo- gists then understood, for the first time, how glandular organs might produce secretions and yet not discharge them into excretory ducts, and this indeed pointed the way to the explanation of the function of the ductless glands. (Flint.) The production of glycogenic matter is, however, not peculiar to the liver; forvbefore birth the placenta performs a similar function, and at about the time that glycogenic matter begins to appear in the liver, the glycogenic organs of the placenta become atrophied, and are lost some time before birth. It is, then, rather with the changes effected in the blood in its passage through the liver, as compared with those effected in the blood in its passage through the spleen, that we are especially concerned. Some very curious observations were made by Lehmann upon the cor- puscles in the hepatic vessels. He estimated that the proportion of white corpuscles in the blood of the hepatic vein was at least five-fold the proportion in the portal blood. He also noted certain differences in the appearance of the red corpuscles, which he explained by the supposi- tion that the hver was the seat of development of these elements, which were formed from the white corpuscles THE NATURE OF THE SPLEEN. 49 and that the blood of the hepatic veins contained a greater number of newly formed, or reju-venescent, blood corpuscles. This at once connects the function of a portion of the liver with that of the spleen. For it has been ascertained that there are similar established points of difference between the blood of the splenic artery and of the splenic vein. There can be no doubt of the fact that the blood coming from the spleen contains a large excess of white corpuscles. Donn6 was the first to call attention to this fact, and his observations have been confirmed by Gray and many others. There is another fact connected with the liver which cannot be satisfactorily accounted for except on the sup- position that the liver is a compound organ, namely, its immense size in the foetus — being at the third or fourth week so large as to constitute one half the weight of the body — for the amount of bile secreted by the foetal liver is insignificant, and bears no proportion to the vascularity of this organ. It wiU be recollected that in the foetus, up to the moment of birth, most of the blood returned from the placenta by the umbilical vein passes through the liver before it reaches the heart. The blood of the umbilical vein reaches the ascending vena cava to gain the heart in three difierent ways. Some passes directly into the vena cava by the ductus venosus; another, and the principal portion, passes first through the portal veins, and then through the hepatic veins, whilst a third portion enters the liver directly, and is ultimately returned to the vena cava by the hepatic veins. The biliary function of the liver is essentially connected with that of the intestine, and hence it is in abeyance in the foetus while the function of a ductless blood-gland is alone performed. Immediately after birth, and concurrently with the sudden arrest of the passage of placental blood through the liver, this organ, notwithstanding that it assumes its biliary function, at first, becomes absolutely lighter, and although the rest of the body grows rapidly, this decrease in weight is not recovered from until the conclusion of the first year. After this period the liver, though it increases in size, grows more slowly than the, body, so that its relative weight, in regard to the body, which was one to eighteen 50 THE NATUEB OF THE SPLBEN. just before birth, becomes gradually less and less. At about five or six years of age it has reached the proportion maintained during the rest of life, viz., one to thirty-six ; and it is worthy of remark that the relative weight of the left lobe to that of the right, which is about one to one and a half immediately before birth, undergoes a diminu- tion afterwards. Thus at a month old it has been found to be as one to three ; and in after life the proportion is generally one to five. This decrease in size takes place at the same time that the biliary function is on the increase, and is sufficiently accounted for by the cessation of the blood-gland function of a portion of the liver. After birth, as the liver decreases in size, so the spleen as rapidly increases in size, and in comparison with the weight of the body, is as heavy a few weeks after birth as in the adult. Evidence in favour of the liver's supplementing the func- tion of the spleen may be obtained from the experiment of removing the spleen. The experiment of removing the spleen seems to have been performed in very early times. Pliny says — " That animals will live after this part has been torn out" (Lib. xi, c. 30) ; and the same fact is noticed in the Talmud, (Ginzburger, Medic. Talmud, p. 11). Haller cites various instances in which the spleen has been lost in the human subject ; particularly Leon; Fioravanti, Tesoro dellaVita Umana, b. ii, c. 8, Phil. Trans,, No. 451. The removal of it from the dog is an experi- ment which has been repeated over and over again, (see Haller, t. vi, p. 421. We find that animals, and even human subjects, have lived without the spleen, and en- joyed tolerable health. Sometimes the experiment has been fatal ; but not from the loss or interruption of any function, that could be ascribed to the spleen. We find that dogs have been lively, fat, and even plethoric ; that they have had good appetites ; in short, imperfection in the digestive process is the only thing noticeable, and the liver is the only organ which has suffered, and that in only a few instances. The inference usually drawn from these experiments is, that the spleen is a useless organ ; or that the function of the spleen is of little importance in the economy. Such an inference is of course absurd. The more correct inter- THE NATURE OF THE SPLEEN. 51 pretation would probably be, that some other organ sup- plements the function of the spl^n, just as one kidney can accomplish the function of urinary excretion after the other has been removed. Moreover, in this case the single organ remaining does not apparently undergo enlargement ; and there can be no reason why the liver may not accom- plish the function of the spleen after the removal of this organ, and without undergoing any enlargement, except, as mentioned, in a few instances. To return to the liver. Having shown above that the liver may be regarded as a union of two organs, and that it performs two functions — one function being similar to that of the spleen, and exhibited in the altered condition of the blood of the hepatic veins — we now draw attention to its remaining function, namely, the bOiary, in order to connect this office of the liver with that of the alimentary canal, and to account for the absence of that fiinction on the left side of the body, in connection with the spleen. The first point which claims our attention is, that no liver exists in those annulida which are destitute of a distinct alimentary canal, such as the trematoda, tseniada, and acanthocephala ; nbr yet in the coslenterata, much less in- the protozoa. The liver, in its simplest condition, is a mere inflection of the mucous lining of the alimentary canal, forming a small csecal recess, or follicle. The capillary vessels ramify upon the parietes of -the follicles, which pour their secretion into their internal surface, whence it is conveyed to the alimentary canal to be mingled with the ingesta. In this, its most rudimentary form, the liver would appear to be present in the langinella, a small cilio- brachiate polypus. The next most elementary form of the hepatic caecum is seen in the single lengthened foUicle discovered by Owen in the ascaris halicornis. The follicle opens into the alimentary canal at about one third from its oral extremity. Among the annelida, as the medicinal leech, the liver is r^resented by numerous simple caecal pouches, appended to each side of the digestive canal. ' The next step in the complication of the organ is observed in the lengthened filiform tubercles, which are connected with the sides of the canal in the aphrodita. They termi- nate in a small oval sac. In other species of the same genus, and in the arenicola, they display a tendency to 52 THE NATHEE OP THE SPLEEN. ramify by developing small coeoal pouches from their sides. In the class inseota thf hepatic caeca vary in progressive development from the simple vascular dilatations observed in the digestive canal of the lampyrus splendidula, or the simple csecal tubules of the carnivorous cicindela to the numerous csecal follicles of the dytiscus, or to the more lengthened tubuli of the blatta orientalis. Throughout the whole class, the character of the liver is tubular. In araohnida the csecal follicles are short, and terminate at their extremities in a cluster of numerous rounded vesicles, -which give to the organ a lobulated appearance. In the class Crustacea the simple csecal follicle of insecta becomes branched and ramified, of which we have an example in argulus foliaceus. In astacus fluviatilis it is more branched ; and in the pagurus striatus the liver is composed of an extraordinary assemblage of ramified follicles. In the hepatic organ of the squilla mantis we perceive a remark- able transition from the simple branched and ramified follicle of the lower Crustacea, to the higher forms of the organ in the molluscous classes in which it is solid and symmetrical. In vertebrata the liver is close and com- plex in its structure, and always directly connected with the alimentary canal. This intimate connection is best seen during the period of the development of, this organ. Its development has been frequently traced from a conical protrusion of the intestinal canal, surrounded by a soft mass, or blastema, in which, by a subsequent process of growth, the ducts are formed. Through the whole of the vertebrate series the biliary apparatus is so intimately connected in its origin with the alimentary canal, that the absence of the alimentary canal from any cause would necessarily entail the absence of the biliary apparatus. Now if, as we have shown above, there is reason to believe that the small intestine of the left side of the body is undeveloped, the absence of the bUiary apparatus on that side is fully accounted for. But as we have explained, there is also reason to regard the liver in the vertebrata as a combination or union of two organs, a biliary apparatus and a blood-gland. Hence, on the left side of the body, the non-develop- ment of the alimentary canal, together with the absence of the biliary apparatus, gives rise to the. separate exist- THE NATURE OF THE SPLEEN. 53 enoe of the blood-gland, the spleen. These two organs are not essentially connected in the animal series, for we know that the biliary apparatus may exist independently of the spleen, for such a condition is maintained through- out the invertebrate classes. The term blood-gland has been frequently used in these pages when speaking of the spleen, and its lateral homo- logue, a portion of the liver, in accordance with the nomenclature of recognised authorities. The term, it must be confessed, has been used by them rather from the circumstance that the spleen is intimately connected with the sanguiferous system, and that it is unprovided with a special duct, than from any definite views with regard to its office. The function of the liver, in its capacity of a blood-gland, is performed in its highest degree in the foetal condition, when much of the bloofl from the placenta passes through its substance. The nature of this office may be the more readily explained by referring, by way of analogy, to the lymphatic system of vessels. It is well known that for the most part the lacteals and lymphatics, which may be regarded as consti- tuents of the vascular system, pass through certain small vascular bodies named lymphatic glands, so that both the chyle and lymph are sent through these glands before being mixed with the blood. It is found, moreover, that the lymph and chyle contain a greater proportion of fibrine, and are consequently more perfectly coagulable after pass- ing through these glands, and it is also observable that the proper corpuscles of the chyle and lymph are most abundant in that which is obtained from the lacteals, or lymphatics, which have just passed through these glands. From this latter circumstance, it has been supposed that these cor- puscles, though probably also generated elsewhere, in the lymphatic and lacteal vessels, are principally produced in these glands. In a gland a large number of plexiform lymphatic vessels are collected into a compact mass of small compass. A system of lymphatic vessels is super- added in all classes of vertebrate animals. Such, however, is not the case in the invertebrata. When we compare with the above description some points connected with the course of the circulation in the foetal con- dition, the structure of the spleen, and the composition of 54 THE NATUBB OF THE SPLEEN. splenic and hepatic blood, a remarkable coincidence will be apparent. It will be remembered that the blood from the placenta, after proceeding by the umbilical vein, mostly passes through the blood gland, the liver, before it is mixed with the blood of the general circulation of the body, so that this organ holds the same position in relation to the sanguiferous system that the lymphatic gland does to the lymphatic system; and the total absence of lymphatic glands in the placenta appears to account for the preseuce of this gland at the point of ingress of the placental blood into the general circulation. A gland for the passage of blood so situated would both obstruct the entrance of injurious elements into the body, and impress new cha- racters upon the placental blood, fitting it for the pur- poses of the circulation. Although the combination of the blood-gland with the biliary apparatus, in the case of the liver, renders the structure obscure, yet in its lateral homologue the spleen, the structure is quite in harmony with the view that the spleen is a highly deve- loped glandular structure, analogous to the lymphatic gland, but differing as much from a lymphatic gland as an arterial trunk differs from a lymphatic vessel. By its higher degree of development the spleen is adapted to the requirements of the arterial and venous systems. The spleen then is to be regarded as a sanguiferous gland attached to the sanguiferous system, and performing a similar function for the arterial to that performed by the lymphatic gland for the lymphatic system. With regard to the hypothesis of sanguification, the spleen probably has, no more power of sanguification than a lymphatic gland has of manufacturing lymph, although in both oa^s they are capable of impressing definite characters upon the fluid passing through them. There are three functions, at least, we may expect from the spleen, if regarded as a sanguiferous gland, namely, the arresting of effete or injurious elements in the blood, the adding of leucocytes, or white corpuscles, and the increasing of the fibrine and albumen of the blood. Now the investigations of Lehmann, BIclard, Gray, and others, have shown un- doubtedly, although its significance has not hitherto been understood, that the blood of the splenic vein differs from that of the splenic artery, in having a large excess of THE NATURE OF THE SPLEEN. 55 white corpuscles, a diminution in the proportion of red corpuscles, and an increase in the fibrine and albumen. Although the blood of the hepatic veins originates from a more complicated source, we may still expect to find a lai^e excess in the white corpuscles, and it does show an excess of these corpuscles, at least fivefold the proportion found in the portal blood. Pathological investigations strongly corroborate the above views as to the nature of the spleen. The irregularity in the situation of the Spleen has never been satisfactorily accounted for. In the chelonia the spleen is bound to the commencement of the transverse arch of the colon ; and amongst the sauria, in the crocodile it is placed behind the stomach, at the back part of the abdomen, but on the left side of the mesial line ; and in ophidia this organ, in, the large boa for instance, is found at the left side of the pylorus, just at the commencement of the intestine and intimately connected with the pancreas. In pisces the position is similar in nearly all families, being placed in apposition to the side of the stomach, or to some part of the intestinal canal, by means of a fold of the mesentery. In some few fish, as in the tench, it is in intimate connection with the left lobe of the liver. May not this want of regularity in the situation of the spleen be accounted for by its having missed its connection with the biliary apparatus of its own side of the body? In the higher mammaha, in which it presents by far its greatest development, it maintains a position symmetrical with, and laterally homologous with, the liver. The separate splenculi, and also the deep notching of the anterior mar- gin of the spleen, in the human subject, bring to mind the multiple condition of this organ in some animals, as, for instance, in" the porpoise. In the dolphin there are many lobes. Both these conditions are liable to occur in the case of all lobular organs, and are noticed in the liver, pancreas, and kidney, in various animals. The dze of the Spleen in proportion to the size of the body is a subject which has engaged the attention of many observers, and without any satisfactory conclusion. As we have before mentioned, in the cetacea, in which the bulk of the blood is larger, the size of the spleen is smaller in proportion to the size of the body than in any other of the 56 THE NATURE OP THE SPLEEN. mammalia ; whilst in the cheiroptera, as, for instance, in the bat, it is larger in proportion to the body than in any other order of this class. It is much larger, in felidee than in the other orders of the carnivora ; whilst in the kangaroo it is small. In birds the spleen is generally of small size as compared with the body; much smaller than in the mammalia. It is large in the cormorant and small in the puffin and ostrich. Descending in the vertebrate series, in reptilia the spleen appears cohsiderably reduced in size and importance. In the crocodile it is of larger size than in any other reptilia. In the ophidia this organ is very small, being reduced to its minimum of deve- lopment in this class. Moreover, the Malpighian bodies which form so important an element of the spleen in the mammalia and birds, are absent in the reptiles. In pisees the spleen is generally present, but is of small size ; in the lepidosiren it is exceedingly small ; in the lamprey its presence has been thought doubtful ; and in the lancelet, the most lowly organised of the vertebrata, it seems to be absent. Various hypotheses have been put forth in explanation. It has been suggested that the size of the spleen might bear some relation to the nature of the animal's food. Thus in mammalia, the spleen is found to have a much larger proportional size in carnivora and insectivora than in the remaining orders. It is consequently largest when the intestinal canal presents the least complex structure, where the digestion is most rapidly performed, and conse- quently when the new material is more suddenly added to the blood ; and we have seen above how congestion of the portal system may impede the passage of the blood through the spleen. It is quite possible that this may, to some extent, influence the size of the spleen ; and there can be little doubt but that " in the amphibia its large size and its peculiar lax and distensile texture are in per- fect harmony with the requirements of the animals of this class, being peculiarly adapted as a reservoir for the blood, which accumulates in the venous system during the sus- pension of respiration." (Gray.) These explanations are not sufficient to meet all cases. It is probable that a clue is to be found in the application of some general law of nature, modified to some extent by the THE NATURE OF THE SPLEEN. 57 habits of each race of animals. We find, in fact, that, if we may judge from its size, the importance of the spleen seems to diminish successively from mammalia to birds, then to reptiles, and from them to fishes ; and we also find that the liver among the vertebrata, proportionately to the body, becomes progressively larger in passing from the mammal to the fish. For instance, in the mammalia the spleen presents by far its greatest development of struc- ture, and this, no doubt, partly depends upon the greater general completeness and requirements of their organiza- tion. But the liver in mammalia is very much reduced in size, and is more compact and firm than in the lower vertebrata ; and may not the small size of the liver be to some extent accounted for by the compensating function of the largely developed spleen 1 Although the above may afiFord sufficient explanation of the fact that the spleen is larger in the mammal than' in the fish, it does not account for the diflTerence of size in the various orders of each class. But may not the proportional size of the spleen in each order be also a question of development ? for, on examination, it wUl be found that the proportional size of this organ frequently bears some relation to the development of the lateral organs, as exhibited in the size and complex structure of the limbs, especially of the upper extremities If we take extreme cases, this will be more apparent j in the mam- malia, by way of illustration, the largest proportional size of the spleen is to be found in the bats, and the smallest in the whales; whilst it is in the bats we meet with the highest development of the upper extremities, and in the whales the lowest. In the Felidce, with highly developed claws, as, for ex- ample, in the Hon, the spleen is of much larger size than in other orders of the camivora ; whilst in the kangaroo the spleen is proportionately small, this reduced bulk co- existing with the diminished size of the upper extremities. The small size of the spleen in the marsupials and mouo- tremes is, however, capable of another explanation. In the Pachydermata, as a rule, the spleen is small. The seal, phoca vitulina, would, at first sight, appear to be an exception ; but as explained above, in amphibia and other animals of allied habits, the spleen, by its large size and dia- tensile structure, serves as a reservoir for the blood which 58 THE NATURE OF THE SPLEEN. naturally accumulates in the inferior cava and the hepatic reservoir, and passes through the channel in the portal system to the spleen, when the venous system ia ob- structed as a result of suspended respiration. In the class Aves the spleen is generally of small size, as compared with the body — much smaller than in the mammalia — in accordance with the descending scale of general development. The liver, moreover, is more largely developed than in the mammal. The spleen is large! in the cormorant, and small in the ostrich and puffin, and large, as may be expected, in the diving moor-hen. In the Eeptilia, as we descend in the scale of the verte- brate series, the function of the spleen appears to be con- siderably reduced in importance, as shown by the extreme diminution in its size. The liver is larger than in birds. The crocodile, as compared with the sei-pents, affords an- other example of the larger size of the spleen, coexisting with the higher development of the limbs. This organ is larger in the crocodiles than in any other reptile ; and in the ophidia the spleen is very small : its size has been estimated, as compared with the body, at 1 to 11.150. In the boa it hardly exceeds in size a common pea. The most prominent structural difference in the reptilia is the absence of Malpighian bodies, which form so important an element of the spleen in the mammalia and birds. In Fisces the spleen is universally present, but its small size in proportion to the body confirms this view and shows that it is an organ of less functional importance than in the mammalia. The liver is larger than in birds. Having shown above that the spleen is, anatomically, the left lateral homologue of the liver, we now recapitulate the various considerations for regarding the spleen and liver as mutually related, physiologically. From independent investigation, physiologists have come to regard the spleen as a blood-gland ; that ia to say, an organ devoid of any proper duct, and whose office is to impress certain characters upon the blood in its passage through its tissues. There has, however, been much dif- ference of opinion with regard to the precise nature of the change effected in the sanguineous fluid. Some have gone so far as to believe that it supplies all the germs which are ultimately to become blood -corpuscles ; but, as Pro- THE NATURE OF THE SPLEEN. 59 fessor Owen has pointed out, although the spleen receives more blood than is needed for its nutrition, it yet receives too small a portion of the circulating mass to have any very definite influence on the manufacture of the blood. Since, however, the splenic vein is the largest constituent channel of the portal vein, it is inferred that such changes as are effected in the splenic locality probably relate to the function of the liver, to which the altered blood is exclu- sively carried. To this it has been objected that, no instance of an arrangement of a like nature can be adduced, of one organ's elaborating properties that they may be removed by another ; and also that the splenic blood does not differ in its destination from the blood of all the chylopoietio viscera. What, however, is exceptional is this, that the splenic blood is poured into the portal system of the oppo- site side of th^ body, and this fact leads to the conjecture that not only is the biliary apparatus absent on the left side of the abdomen, but that the liver itself is a combina- tion of two organs, one resembling its lateral homologue, the spleen — a blood -gland — and the other a biliary organ. Now, upon an examination of the liver, we find that it has a double vascular supply, difiering in this respect from'all the other abdominal viscera. It is supplied by the hepatic artery, a vessel corresponding with the splenic artery, and also I by the portal vein, which is distributed after the manner of an artery; and the blood from the hepatic artery, as is also the case with that from the splenic artery, falls ultimately into the portal system before gaining the hepatic veins. The tissues supplied by the hepatic artery differ from those supplied by the portal vein, which is dis- tributed exclusively to the hepatic lobules. It may be objected that this double vascular supply is not conclusive evidence as to the double nature of the liver, for a similar arrangement exists in the case of the lung, which is supplied by an artery and a vein, and the vein is distributed to the pulmonary lobules after the manner of an artery. An examination of the nature of the lung will dispose at once of this objection; for the lung is a compound organ, and is to be regarded as a combination of the air bladder and the gills ; and there are not wanting indications of the combination of their separate functions ; and in the case 60 THE NATURE OF THE SPLEEN. of the liver, the fanction of each of its component parts can be recognised. The discovery of the glycogenic function of the liver has directed the attention of physiologists to the liver, in order to detect the existence of two distinct portions ; but their labours have not been attended with any very satis- factory results, so far as the isolation of two organs is concerned ; and since the glycogenic function is also performed in other parts, and the spleen itself does not perform a similar office, we seek in the liver some vestige of a fibro-cellular structure, supporting an arterial and venous plexus, similar to that found in the spleen. Now in the disease of the liver known as cirrhosis, in which there is a partial atrophy of the biliaiy secreting portion of the liver, this tissue becomes evident. But it, is in the blood of the hepatic veins that we find the greatest evidence of the liver's performing a similar function to that of the spleen. Lehmann has detected the presence of white corpuscles in the blood of the hepatic vein, and has esti- mated that their proportion is at least fivefold the propor- tion in the portal blood ; and DonnI has called attention to the fact, and his observations have been confirmed by Gray and others, that the blood coming from the spleen also contains a large excess of white corpuscles. That the liver has other functions in addition to that of secreting bile, is apparent from its condition in the foetus ; for at an early period of foetal existence it is so large as to constitute one half the weight of the whole body, and the amount of bile secreted is quite insignifi- cant, and bears no proportion to its vascularity. A large portion of the blood from the placenta passes through this organ before entering the general circulation. At birth, not- withstanding that it assumes its biliary function concur- rently with the establishment of the office of the intestine, it becomes considerably lighter, and up to the age of five or six years, although the secretion of bile iS largely on the increase, it becomes gradually less and less. This is sufficiently accounted for by the cessation of its blood- gland function ; moreover, the spleen after birth as rapidly increases in size as the liver diminishes, and in comparison with the weight of the body is as heavy a few weeks after birth as in the adult. THE NATUBB OF THE SPLEEN. 61 Further evidence of the liver's supplementing the func- tion of the spleen may be obtained from the experiment of removing the spleen ; for the inference drawn from the fact of the small amount of disturbance to the system following this operation at once points to the conclusion that some other organ carries on its function, just as one kidney can accomplish the function of urinary excretion after the other has been removed, and without any apparent en- largement ; and the only organ which has suffered after removal of the spleen has been the liver. All these cir- cumstances, taken in combination with the anatomical position of the liver and spleen, explain the mutual physiological relationship of these two organs. It is now necessary to account for the absence of the biliary apparatus on the left side of the body in connection with the spleen. No liver exists in those animals which have no alimentary canal. In all animals having a liver this organ is intimately connected with the alimentary canal, and during the period of development this organ can be traced to a conical protrusion of the mucous membrane of the intestinal canal, surrounded by a soft mass, or blastema. Through the whole of the vertebrate series the biliary apparatus is so intimately connected with the ali- mentary canal, that the absence of one would necessarily entail the absence of the other ; so that the undeveloped condition of the small intestine on the left side of the body fully accounts for the absence of the biliary appara- tus on this side ; and since, on the right side, the biliary apparatus is connected with the blood-gland, the two together constituting the liver, the cause of its absence, in combination with the spleen, is sufficiently clear, and these two organs are not necessarily connected together, for the biliary apparatus exists without the spleen through- out the invertebrate series. The pancreas has nothing whatever to do with the spleen. It is situated on the right side of the mesial line of the body, on the same side as the liver, with which it is functionally connected. The liver is not the result of the union of a pancreas with a spleen, nor would the spleen, if united with the pancreas, form a liver. We have, in the next place, to consider the nature of the function of the spleen. It has been denominated a 62 THE NATURE OF THE SPLEEN. "blood-gland," but with very vague notions with regard to its functions. The liver, as we have seen, is composed of a blood-gland and a biliary apparatus ; but its office as a blood-gland is performed in its highest degree in the foetal condition, when much of the blood from the placenta passes through it. It is well known that in the lacteal and lymphatic systems both chyle and lymph are for the most part sent through small vascular glands before being mixed with the blood. Just in the same way the blood from the placenta passes through the blood-gland con- nected with the liver, before it is mixed with the blood of the general circulation ; so that this organ bears the same anatomical relationship to the sanguiferous system that the lymphatic gland does to the lymphatic system ; and the entire absence of lymphatic glands in the placenta appears to acootint for the presence of this gland at the point of ingress of the placental blood into the general circulation of the foetus. Although the combination of the blood-gland with the biliary apparatus, and the ultimate arrest of its function, obscure its structure, in the case of the liver, its lateral homologue the spleen presents a structiire in harmony with the view that it is a highly developed glandular organ, attached to the arterial system, somewhat analogous to a lymphatic gland, but diffehng as much from an ordinary lymphatic gland as an arterial trunk differs from a lym- phatic vessel. The lymph, or chyle, after passing through a gland, contains a greater proportion of fibrine, and a larger number of proper white corpuscles ; moreover these glands appear to have the power of obstructing the entrance of in- jurious elements into the blood. Now the investigations of Lehmann, BIclard, Gray, and W. Miiller, have shown un- doubtedly that the blood of the splenic vein presents a very large excess of white corpuscles, a diminution in the proportion of red corpuscles, and an increase in the fibrine and albumen ; and that the blood of the hepatic veins also, shows- a large excess of white corpuscles, at least five- fold the proportion found in the blood of the portal veins. Diminution in the proportion of effete corpuscles in the blood in passing through the spleen, in a very marked degree, has been noted. Enlargement of the Spleen, as the result of blood-diseases, corroborates these views. THE NATURE OF THE SPLEEN. 63 The small size of the spleen, as compared with the liver, in the foetal state, is to be explained by the fact that the umbilical vein exists only on the right side of the body. The lobed and multiple condition of the spleen in some animals, is nothing more than what occurs in the case of other lobular organs, such as the liver, kidney, pancreas, etc. The size of the spleen, in proportion to the size of the body, is a question of development, modified by the habits of the animal, the size of the liver, and the degree of development of the lateral organs, etc. The Spleen is not the undeveloped liver of the left side of the body, nor is it the parenchyma of the liver dis- united from the pancreas ; nor is it a blood-gland in the mesial line of the body, having no homologous relationship with the liver. The Spleen is a sanguiferous gland, situated on the left side of the abdominal cavity. It is the left lateral homologue of a portion of the liver; the liver being a combination of a sanguiferous gland and a biliary appa- ratus. In the course of this investigation the following points in human anatomy receive elucidation. The peculiar shape of the stomach, terminating at one end in a cul-de-sac, and at the other in the pylorus. The opening for the oesophagus not being in the centre, but much nearer the great end of the stomach. The direction of this organ, stretching into the right lateral region. The marked difference which exists in its various coats, and their undeveloped condition as they approach the great cul-de-sac. The stomach being supplied by one artery instead of by two vessais, one on each side ; so that it depends upon neighbouring organs for its vascular supply. The lym- phatic vessels at the cul-de-sac forming a distinct set from those belonging to the rest of the stomach. The sympa- thetic system of nerves supplying both surfaces. The contraction which exists during the process of diges- tion more or less dividing the stomach into two cavities ; and the fact that pain at the left end of the stomach is felt on the left side of the head, and that at the right side of the stomach on the right side of the head. The situation of the small intestine, commencing at the 64: THE NATDEB OF THE SPLEEN. upper part of the right lateral region, and passing to the middle line before joining the large intestine. That the various glands, Peyer's glands in particular, are not placed symmetrically on each lateral half of the bowel. That this intestine is supplied by one artery and vein. That the large intestine, instead of being supplied by one vessel, as in the case of the small intestine, is supplied by two vessels ; and that its situation is in the mesial line of the body. The nature of the vermiform appendix. The large size of the foetal liver ; its diminution after birth. That it is situated in the right hypochondriac region, rather than in the mesial line. The nature of its lobes. That although the largest viscus in the abdominal cavity, it is supplied by only one artery from the aorta,, instead of by two. That there are not two portal systems, one for each side of the abdomen. That the umbilical vein is connected with the liver in the foetal condition. That there is but one umbilical vein instead of two, whilst there are two umbilical arteries. That there is no biliary apparatus, nor small intestine, on the left side of the body. That the lacteal system is much smaller on the left side of the abdomen than on the right, and is not connected with the small intestine. The small size of the spleen before birth, and its rapid increase afterwards. Its distension in cases of internal congestion. The large size and peculiar course of the splenic vein. That there is one splenic artery instead of two. The unsymmetrical form of the spleen, and its lobular condition. That the spleen has no biliary function. Enlargement of the Spleen results from an abnormal condition of the blood, as in Typhus, Typhoid, Cholera, Pysemia, Erysipelas, Scarlatina, Measles, Dyscrasia, Ague, Scurvy, Purpura, Chlorosis, Eheumatism, and Tubercu- losis. In conclusion, it may be added that the foregoing in- vestigations into the anatomy and physiology of th6 abdo- minal viscera afford many suggestions as to the appropriate treatment for the relief of various affections of the Stomach, Liver, and Spleen.