5U+ Sr ?i£* author’s abstract of this paper issued BY THE BIBLIOGRAPHIC SERVICE, JUNE 2.7 Reprinted from The Journal of Comparative Neurology, Vol. 33, No. 3, August, 1921 THE LIBRARY OF THE ’M « . k» « I* ON THE GROWTH OF THE LARGEST NERVE CELLS IN THE SUPERIOR CERVICAL SYMPATHETIC GAN¬ GLION OF THE ALBINO RAT—FROM BIRTH TO MATURITY CHI PING The Wistar Institute of Anatomy • " SIX CHARTS AND ONE PLATE INTRODUCTION This paper contains observations on the largest nerve cells in the superior cervical sympathetic ganglion of the albino rat. The purpose of this study is to trace the growth of these cells by their increase in diameter in relation to the age and size of the animal. In order to compare the possible differences in growth in the sympathetic nerve cells due to sex, a male and a female rat of each age were used throughout the series of observations. The author desires to express his sincere appreciation and gratitude to Dr. M. J. Greenman for granting him the privileges and facilities of the Institute for this investigation, and to Dr. H. H. Donaldson, under whose direction the work was carried on and whose valuable advice and guidance enabled him to formu¬ late his results. MATERIAL The material used for this investigation consisted of sixteen pairs of albino rats, of known ages, from 1 to 365 days. Besides these, two females of 540 days and 570 days, respectively, were used for comparison. All these were obtained from the animal colony at The Wistar Institute and belonged to the so-called 'standard strain.’ In selecting the specimens, five-day intervals were taken between each two ages from birth to thirty days, but from this age onward greater intervals were used. The body weight, body length, sex, and age of each rat were recorded. 281 282 CHI PING For comparison and control a second limited series of inbred albino rats was also used. The data for this series are given on page 303. Up to the introduction of this series the paper deals only with albino rats of the ‘standard’ strain. TECHNIQUE The rat was etherized and, after the necessary measurements had been noted, was completely eviscerated. The superior cervical sympathetic ganglion was removed from each side. In the removal care was exercised to avoid distortion of the tissue, for mechanical injury to the ganglion is likely to affect the size and shape of its cells. As the ganglion is small, it was deemed necessary to remove it in the mass of other tissues which closely invest it. Both ganglia from each rat were prepared, but only one was used for measurements. No distinction between right and left was made in the record. Aiming at a satisfactory preservation of the natural size of the cells, I followed King’s (TO) recommendation of Bouin’s solution for fixation. The ganglia from older rats were fixed in the solu¬ tion for twenty-four hours, while for those from the younger ones—from birth to twenty-five days old—the period was reduced to twelve hours. Such a reduction of the fixation period has given satisfactory results. The specimen was washed in different grades of alcohol, from 70 to 98 per cent, containing a small amount of carbonate of lithium. By so doing the yellow tinge given to the tissue by the fixation was completely removed. The specimen stayed in the alcohols of lower grades for twelve or more hours, and in the 90 and 98 per cent alcohol for about one hour. It was finally trans¬ ferred to cedar oil for twenty-four hours for complete dehydra¬ tion. Paraffin of 52° was used for imbedding. By employing an electric bulb above the container the paraffin was kept melted only in its upper layer in the jar, the specimen sinking to the contact line between the melted and unmelted paraffin. Under these conditions the specimen could be left in the paraffin for thorough penetration as long as seemed necessary without danger of overheating. SYMPATHETIC CELLS I ALBINO BAT 283 Serial sections of the entire ganglion were cut 8 n in thickness. Heat from an electric bulb was used in flattening the sections. The slide was placed underneath the bulb, so that the water that served to float the sections on the slide, also chilled them from beneath, when they were spread by the heat. The procedure in staining was as follows: The sections were passed from xylol down through the graded alcohols to water, and then put for five minutes in a saturated solution of lithium carbonate, after which they were stained for two or three minutes in a one-third saturated solution of thionin. They were then passed up through the graded alcohols to xylol and mounted in acid-free balsam. So far as possible, the plane of section was made perpendicular to the short axis of the ganglion, thus giving the maximum area. MEASUREMENTS OF THE CELLS AND NUCLEI The cells and nuclei of the ganglion were measured with an eyepiece micrometer, using a Zeiss ocular no. 6, and objective, 4 mm. Each division in the micrometer scale was equivalent to 4.47 /j. The measurements were made in the following way: In the case of each specimen a section at the middle of the series was selected. Starting both ways from this, four more sections were selected, two in each direction, by skipping every other section. In this manner five sections altogether were chosen and marked for study. In each of the five sections the two largest cells were measured; thus ten cells in all were measured in each ganglion. There were four principal points kept in mind when selecting the cells for study: First, the cells must be the largest in the section; second, they must be uninuclear; third, the nucleus must be located at or near the center of the cell and must be fairly large; fourth, in the nucleus at least one nucleolus must be present. Under these conditions, the measurements made on the cells and nuclei are considered to represent the maximal longitudinal and transverse diameters of each cell and nucleus taken close to their median planes. It was often found in this study that 50158 284 CHI PING the boundaries of a cell body were obscure. Furthermore, the distribution of the Nissl granules was rather irregular (as will be described later), so that neither the longitudinal nor the transverse diameter could be measured according to the extent of the stainable mass. After the measurements had been taken, a sketch of the section with the two cells measured therein was made, and the nucleoli in these cells were noted, so that in making measurements for the second time the same cells could be identified by their location and the number of the nucleoli. As a matter of routine, the cells in each ganglion were measured twice, a considerable time being allowed to elapse between the first and second measurements. The procedure in measuring did not follow in the order of age or of body weight of the animal, as given in the tables, but was purposely haphazard, and in making measurements for the second time, the records were taken without referring to those already made. The values used are the means of the two series. By this procedure prejudice was avoided and a more accurate determination of the size of the cells and nuclei obtained. The records thus made were tabulated in detail, but the averages of the values for the ten cells in each ganglion are those used for the tables, charts, and discussion which follow. The individual data have been filed in the archives of The Wistar Institute. The square roots of the products of the longitudinal and trans¬ verse diameters of the cells and of the nuclei, respectively, for each ganglion were averaged, and the mean was multiplied by 4.47, the value in of one division of the eyepiece scale. In table 1 the diameters of the cells and nuclei thus computed are arranged according to age, and in table 2 according to the body weight of the animal. Based on the records in tables 1 and 2, charts 1 and 2 were plotted. Chart 1 shows on age the graphs for the diameter of the cells and nuclei in micra and chart 2 the same relations on body weight. In the graphs for the cells in chart 1 we see in the increase before puberty only chance variations between the male and the female in diameter of the cell body, but after the rat has attained SYMPATHETIC CELLS: ALBINO RAT 285 the age of eighty days (body weight about 100 grams) which is the period of puberty (Donaldson, ’15, The Rat, p. 21) there appears a tendency for the cells to be larger in the female than in the male. It will be noted, however, that at the age of eighty- nine days, and also at 250 days, the male exhibits larger cells than the female of the same age. This discrepancy is explained when we take the body weights of the males into consideration. As given in table 1, the body weight of the male rat eighty-nine days old is twice that of the female of the same age, and the dis¬ crepancy is even greater in the case of the male at 250 days. These males should be expected to have larger nerve cells by virtue of their body weight, and when a correction is made for it, the values for the male cells should fall below those for the female at these ages also. In general one may say that the female, after reaching puberty, has these cells larger than the male, if the body weight of the male does not too greatly exceed that of the female. As regards the nucleus, however, chart 1 exhibits a less clearly marked sex difference. The fact that there is a better growth of the cell bodies in the female is more clearly illustrated in chart 2, in which graphs for the diameters of the cells and nuclei have been plotted on body weight. From birth to the time just before puberty, the varia¬ tions in the growth of these cells in the two sexes are similar to those shown in chart 1. Just before puberty, when the rat weighs about 60 grams, the female becomes gradually more advanced in the growth of these cells and overtakes the male of the same body weight. The growth of the nerve cells in the female also shows a more regular course than that of the male. The growth of the nuclei at the corresponding ages of the two sexes follows in the same manner as that of the ceil bodies, although the difference is relatively small. 9 It is proper to keep in mind, however, that when the compari¬ son is made on the basis of body weight, the female is normally the older, and, further, that in several other growth changes the female tends to be precocious; both of these influences would tend to produce larger cells in the female under these conditions. 286 CHI PING TABLE 1 Computed diameters of the largest cells and nuclei according to age. From the superior cervical sympathetic ganglion of the albino rat A B c D E p SEX AGE BODY WEIGHT BODY LENGTH Computed diameter in y RATIO OF DIAMETER OF NUCLEUS TO Cell Nucleus DIAMETER OF CELL days grams mm. cf 1 5.6 50 19.5 11.4 1 : 1.72 $ 1 6.3 51 19.8 10.2 1 : 1.93 cf 5 9.0 63 22.1 10.7 1 : 2.06 $ 5 11.0 65 21.3 10.5 1 : 2.03 cf 11 15.0 77 24.9 13.1 1 : 1.90 $ ii 14.0 73 26.4 13.1 1 : 2.02 cf 16 18.9 83 25.3 13.1 1 : 1.92 9 16 19.0 81 23.1 11.2 1 : 2.06 cf 20 31.7 102 26.4 12.5 1 : 2.11 9 20 29.5 99 23.6 11.8 1 : 1.99 cf 25 23.8 93 26.6 12.6 1 : 2.11 9 25 25.5 95 27.3 12.7 1 : 2.15 cf 29 40.7 112 27.1 12.0 1 : 2.26 9 29 16.4 82 24.8 12.2 1 : 2.03 cf 42 61.4 129 27.0 13.4 1 : 2.01 9 42 43.5 105 27.2 13.2 1 : 2.05 cf 48 105.1 156 29.0 13.4 1 : 2.17 9 48 49.7 120 27.0 13.1 1 : 2.05 cf 60 51.6 124 27.2 13.2 1 : 2.06 9 62 53.8 117 27.1 13.1 1 : 2.07 cf 81 63.3 128 27.4 13.3 1 : 2.06 9 80 83.7 142 26.6 12.8 1 : 2.09 .cf 89 143.5 173 32.4 13.0 1 : 2.49 9 88 73.0 135 29.2 13.2 1 : 2.21 cf 124 151.1 174 27.1 13.0 1 : 2.08 9 124 107.1 157 30.5 13.8 l:-2.21 cf 171 198.2 192 27.0 13.1 1 : 2.05 9 171 123.8 159 30.9 12.8 1 : 2.41 cf 250 230.0 207 36.8 15.4 1 : 2.38 9 250 98.0 160 30.6 . 14.2 1 : 2.15 • cf 365 186.0 203 29.6 • 13.5 1 : 2.20 9 365 170.6 186 31.4 13.5 1 : 2.31 9 540 151.3 184 30.7 13.4 1 : 2.29 9 570 127.1 169 33.4 14.3 1 : 2.34 SYMPATHETIC CELLS: ALBINO RAT 287 On examining the ratios between the values at one day and at 365 days, as shown in columns D and E of table 1, it is found that the cells in the male have increased in diameter 1.55 times, and in the female 1.58 times, while the nuclei in the male have increased 1.17 times and in the female 1.32 times. This shows that the difference between the male and female in the growth of the nuclei in the course of one year is greater than that in growth of the cells, but the cells in both sexes have a greater rate of growth than do the nuclei, as indicated in table 1. Chart 1. Based on table 1 and giving the computed diameters of the cells and their nuclei according to sex—on age in days. Males- Females- The graphs in chart 1 show that the increase in the diameter of the cell body is rapid for the first twenty-five days and then becomes slower. There is a similar change in the nucleus, though the change in the rate of growth in this case is less marked. From 25 to 365 days the diameters of the cells and of the nuclei of the two sexes, have increased as shown in table 3. In column F of table 1 are given the ratios between the diameter of the cell body and that of the nucleus. Generally speaking, the cell has about twice the diameter of the nucleus throughout the series of measurements as given in table 1, but if we consider the ratios carefully, we see that there is an increase in the ratios 288 CHI PING TABLE 2 Computed diameters of the largest cells and nuclei—on body weight—together with the nucleus plasma ratios—from the superior cervical sympathetic ganglion of the albino rat SEX A AGE B BODY WEIGHT c BODY LENGTH D E F NUCLEUS PLASMA RATIOS Computed diameter in ju Cell Nucleus days grams mm. d 1 5.6 50 19.5 11.4 1: 4.0 $ 1 6.3 51 19.8 10.2 1: 6.3 d 5 9.0 63 22.1 10.7 1: 7.8 9 5 11.0 65 21.3 9 10.5 1: 7.3 9 • 11 14.0 73 26.4 13.1 1: 7.2 d 11 15.0 77 24.9 13.1 1: 5.8 9 29 16.4 82 24.8 12.2 1: 6.8 d 16 18.9 83 25.3 13.1 1: 6.2 9 16 19.0 81 23.1 11.2 1: 7.7 d 25 23.8 93 26.6 12.6 1: 8.4 9 25 25.5 95 27.3 12.7 1: 8.9 9 20 29.5 99 23.6 11.8 1: 7.0 d 20 31.7 102 26.4 12.5 1: 8.0 d 29 40.7 112 27.1 12.0 1:10.5 9 42 43.5 105 27.2 13.2 1: 7.7 9 48 49.7 120 27.0 13.1 1: 7.7 d 60 51.6 124 27.2 13.2 1: 7.7 9 62 53.8 117 27.1 13.1 1: 7.8 d 42 61.4 129 27.0 13.4 1: 7.2 d 81 63.3 128 27.4 13.3 1: 7.5 9 88 73.0 135 29.2 13.2 1: 9.8 9 80 83.7 142 26.6 12.8 1: 7.9 9 250 98.0 160 30.6 14.2 1: 9.0 d 48 105.1 156 29.0 13.4 1: 9.1 9 124 107.1 157 30.5 13.8 1: 9.8 9 171 123.8 159 30.9 12.8 1:13.1 9 570 127.1 169 33.4 14.3 1:11.7 d 89 143.5 173 32.4 13.0 1:14.4 d 124 151.1 174 27.1 13.0 o 00 T—I 9 540 151.3 184 30.7 13.4 1:11.0 9 365 170.6 186 31.4 13.5 1:11.6 d 365 186.0 203 29.6 13.5 1: 9.5 d 171 198.2 192 27.0 13.1 1: 7.7 d 250 230.0 207 36.8 15.4 1:12.6 SYMPATHETIC CELLS I ALBINO RAT 289 as age advances, as they are, respectively, 1 :1.72 and 1 :1.93 for the youngest male and female; 1 : 2.11 and 1 : 2.15 at twenty- five days, and 1 :2.34 for the oldest female. This increase is therefore most marked during the first twenty- five days. By comparing the progress from birth to twenty-five days with that from twenty-nine days to 365 days, one can appreciate the rapid increase in amount of cytoplasm within the former period, as contrasted with the slower increase in the course Diameters of Cells and Nuclei in micra -- — - - ^ - — ■ •- A -■ a fY f) vr / / ‘ * d t > t' •y +K- a i - Vi y s S P r — — — — Body weight—gms. I -1 tit mil' 40 30 20 10 25 50 75 100 i 25 150 175 200 250 Chart 2 Based on table 2 and giving the computed diameters of the cells and their nuclei according to sex—on body weight. Males- Females- of a much longer time. It is fair to say, therefore, that the ratios change but slowly after the first twenty-five days. This agrees with the statement of Donaldson and Nagasaka (T8) on the ventral horn cells, that after twenty-four days the nucleus- plasma ratio increases but slowly. VARIABILITY WITHIN A GIVEN GANGLION The number of large cells examined in each ganglion is hardly great enough to permit of satisfactory statistical treatment, but it has been thought worth while to tabulate for each animal the range and average of the diameters of the cells and of the 290 CHI PING nuclei, entering these according to age as in table 1. In a fairly graded series of measurements we may expect to find the average for the series close to the mean of the limiting values, and a little study of table 4 shows this to be the case. MORPHOLOGY OF THE LARGE CELLS Plate 1. (Figures 1 to 7) In considering the morphology of the cells in the superior cervical sympathetic ganglion, it must be recalled that from its cells arise several classes of fibers—pupillodilator fibers, motor, vasomotor, pilomotor and secretory fibers. It is a priori possible, TABLE 3 Increase in diameters of cells and nuclei from 25 to 365 days GAIN DIAMETERS SEX 25 DAYS 365 DAYS Absolute Percentage M U Cells.| d' 26.59 27.26 29.60 31.38 3.01 11.3 15.1 $ 4.12 Nuclei.| cf 12.60 13.45 0.85 6.31 9 12.65 13.54 0.89 6.58 that the several functions thus indicated are correlated with cell characters that are distinctive, but at the moment we have nothing to contribute to the solution of this problem. When young, the cells of the superior cervical ganglion are very similar in appearance to those of the young spinal ganglion, and practically all of them are more or less elongated with processes at one or both ends. Each cell has a large clear nucleus surrounded by a little cytoplasm. This cytoplasm is homogene¬ ous in structure and stains uniformly. Those coarse Nissl bodies, which are found in the cells at later ages, are totally lacking. Usually each nucleus has a single, dark stained, nucleolus, but occasionally there may be found more than one. This condition continues from birth to five or six days of age, when differentia¬ tion begins in the cytoplasm of these immature cells. SYMPATHETIC CELLS: ALBINO RAT 291 TABLE 4 Giving the ranges in the values for the diameters of the largest cells and their nuclei in the superior cervical sympathetic ganglion of the albino rat — arranged according to sex and age SEX AGE BODY WEIGHT CELLS NUCLEI Diameter Range Diameter Range days grams M M M U d 1 1 5.6 19.5 22.0-18.0 11.4 14.0- 9.4 $ 1 6.3 19.8 24.0-17.4 10.2 12.0- 9.4 c? 5 9.0 22.1 25.0-20.0 10.7 14.0- 9.0 $ 5 11.0 21.3 25.0-18.3 10.5 12.3- 9.0 9 11 14.0 26.4 30.0-23.0 13.1 15.0-11.0 d 1 11 15.0 24.9 30.4-22.0 13.1 13.7-11.6 d 16 18.9 25.3 29.0-22.0 13.1 14.0-12.0 9 16 19.0 23.1 25.0-20.3 11.2 14.0-10.0 9 20 295.0 23.6 27.0-19.4 11.8 16.0-10.4 d 1 20 317.0 26.4 29.0-24.0 12.5 14.0-11.0 d 25 238.0 26.6 31.0-23.0 12.6 14.0-11.0 9 • 25 ' 25.5 27.3 31.0-24.7 12.7 14.0-11.0 9 29 16.4 24.8 26.0-22.7 12.2 14.0- 9.4 d 29 40.7 27.1 30.0-24.7 12.0 14.0-10.0 9 42 43.5 27.2 31.0-24.7 13.2 16.0-11.0 d 42 61.4 27.0 30.0-24.7 13.4 16.0-12.0 9 48 49.7 27.0 29.0-24.7 13.1 15.0- 9.0 d 48 105.1 29.0 33.0-26.4 13.4 15.0-12.6 d 60 51.6 27.2 30.0-24.0 13.2 15.0-12.4 9 62 53.8 27.1 30.0-24.0 13.1 15.0-11.6 9 80 83.7 26.6 29.0-25.7 12.8 13.7-11.6 d 81 63.3 27.4 31.5-25.7 13.3 15.6-11.0 9 88 73.0 29.2 31.0-26.0 13.2 14.6-11.0 d 89 143.5 32.4 36.7-28.5 13.0 14.6-11.0 9 124 107.0 30.5 33.0-29.0 13.8 16.0-13.0 d 124 151.1 27.1 28.5-25.0 13.0 14.0-11.7 9 171 123.8 30.9 33.7-29.0 12.8 13.7- 9.7 d 171 198.2 27.0 32.4-24.7 13.1 14.0-12.4 9 250 98.0 30.6 33.0-26.6 14.2 16.0-14.0 d 250 230.0 36.8 39.0-35.6 15.4 18.0-14.4 9 365 170.6 31.4 38.0-28.5 13.5 15.6-12.3 d 365 186.0 29.6 33.7-26.6 13.5 16.0-12.0 9 540 151.3 30.7 34.4-28.3 13.4 14.7-11.0 9 570 127.1 33.4 36.7-29.0 14.3 16.0-14.0 292 CHI PING At birth or during the first days of life there are found among the young cells a few advanced cells which appear conspicuously different from the rest. In these advanced cells the cytoplasm may be already differentiated, even at birth. The stainable Nissl granules, which are of course much finer than those found at later ages, are evenly but distinctly distributed through the entire contents of the cell. Among these granules some clear spaces appear which seem to indicate the differentiation of the homogeneous cytoplasmic mass, and this change in the advanced cells must have commenced during fetal life. When the young cells begin to develop, there is the same dif¬ ferentiation of the cytoplasmic mass, and the stainable bodies arrange themselves in the same way as those seen in the advanced cells. Hereafter more differentaition will be found in them and the}^ grow to resemble the advanced cells in appearance. Taking this as the starting-point in the morphological develop¬ ment, we see among the comparatively large cells in the ganglion four types which probably appear one after the other as here given in the course of growth. Type 1. The advanced cells and the cells which are trans¬ forming into advanced cells, as described above, belong to this type. There is a beginning of aggregation of the Nissl granules and a growth of the unstainable ground-substance in the cells. This type is common during the first twenty days of postnatal life (fig. 2). Type 2. The Nissl bodies are larger than in type 1 and aggregated at the periphery of the cells, forming a ring within which is a comparatively clear portion of the ground-substance surrounding the nucleus. The Nissl bodies stain much darker than in type 1. The nuclear membrane, the nucleoli, and the reticular structure in the nucleus are distinctly visible. There are frequently two or more nucleoli in one nucleus. This type is common in the period between twenty and sixty days (fig. 3), but may also be found at birth (fig. 1). Type 3. Instead of being distributed at the periphery, the Nissl bodies are aggregated around the nucleus, leaving a rather clear space at the periphery of the cell. In some of the cells they SYMPATHETIC CELLS! ALBINO RAT 293 are more crowded at certain regions close to the nucleus, forming dark masses, but some of them may be loosely scattered toward the periphery. It is in this type of cell that difficulties have often been encountered in making out the boundary between the cell wall and the supporting tissue, because the unstained ground-substance is chiefly distributed at the periphery of the cell. This type is common after twenty days of age, but is not infrequently found after sixty days (fig. 4). Type 4. The cells resemble the first type in the arrangement of Nissl bodies, but the stainable bodies are much coarser. There is a considerable evenness in their distribution, though here and there we. find a larger dark stainable mass resulting from their aggregation. Whether this type is developed from the preceding type through modifications in the course of development or whether it is directly derived from type 1, without undergoing the various changes as in types 2 and 3, is a matter to be settled through more detailed investigation (fig. 5). This type is characterized by the dense appearance of Nissl bodies throughout the entire cell body, not leaving much space for the ground- substance, and is common at the age of 124 days and later. In interpreting these several types it is to be recalled that the cells of this ganglion have several different functions and there always remains the possibility of a correlation between function and morphology. Besides the four types of cells described above, binuclear cells are found at all ages until the rat is very old. In recording them, special care needs to be taken. As the cell wall of the sympathetic cell is at times difficult to distinguish, two uninuclear cells in close contract with each other may frequently resemble one cell with two nuclei. In order to avoid error due to such misleading appearances, the precaution has been taken to use an oil-immersion lens in distinguishing the true binuclear cells from those which resemble them. The cells which have their cytoplasm discontinuous somewhere between the nuclei or a constriction at the middle, either slight or pronounced, as the one figured by Apolant (’96, Majer’s ‘cell bridge/ fig. 8, pi. XXIII), were not considered as of the true binuclear type. 294 CHI PING TABLE 5 Giving the number of the cells with two nuclei and of the cells showing pigment, at different ages. Superior cervical sympathetic ganglion—albino rat. In each case the numbers are for one ganglion only SEX AGE BODY WEIGHT BODY LENGTH NUMBER OF BI- NUCLEAR CELLS CELLS WITH PIGMENT cf days 1 grams 5.6 mm. 50 2 0 9 1 6.3 51 2 0 cf 5 9.0 63 1 0 $ 5 11.0 65 2 0 cf 11 15.0 77 1 0 9 11 14.0 73 2 0 cf 16 18.9 83 1 0 9 . 16 19.0 81 1 0 cf 20 31.7 102 2 0 9 20 29.5 99 4 0 cf 25 23.8 93 4 0 9 25 25.5 95 3 0 cf 29 40.7 112 3 0 9 29 16.4 . 82 3 0 cf 42 61.4 129 5 0 9 42 43.5 105 12 0 cf 48 105.1 156 4 0 9 48 49.7 120 2 0 cf 60 51.6 124 5 0 9 62 53.8 117 5 0 cf 81 63.3 128 3 0 9 80 83.7 142 12 0 cf 89 143.5 173 7 0 9 88 73.0 135 1 1 cf 124 151.1 174 15 8 9 124 107.1 157 6 0 cf 171 198.2 192 2 4 9 171 123.8 159 9 0 cf 250 230.0 207 4 0 9 250 98.0 160 5 3 cf 365 186.0 203 6 3 9 365 170.6 186 4 2 9 540 151.3 184 2 4 9 570 127.1 169 3 13 Average of binuclear cells: SYMPATHETIC CELLS: ALBINO RAT 295 Every one of the cells recorded in table 5 had an unbroken layer of Nissl granules around the two nuclei, and at the middle of the cell there existed absolutely no trace of any partition whatsoever which might suggest the contiguous surfaces of two cells closely grown together. Figures 6 and 7 show the binuclear cells in a very young and in a comparatively old rat, respectively. If we determine, by direct measurement, the nucleus-plasma relation in this particular older cell (fig. 7), contrasting the volume of both nuclei with that of the cytoplasm, we find a ratio of 1 : 5.0. This is almost as low as the ratio at birth, and indicates that we are dealing with an increase in the nuclear mass not accompanied by a corresponding increase in the cytoplasm. This, so far as it goes, is an argument against the suggestion that we have here two cells that are fused. According to table 5, the occurrence of binuclear cells is not related to sex. In many cases the numbers of these cells in both sexes are equal or almost equal. There appears, however, to be an increase in their number toward middle age, ranging from sixty days to 365 days, with a possible decrease later. Apolant found cells of the binuclear type in the superior cervical ganglion of an embryo rabbit three weeks old, and states that such cells persist in the older animal, when the cells have been completed anatomically and physiologically. Accord¬ ing to him, this is the result of direct nuclear division; about half of the binuclear cells being formed during embryonic life and the remainder later. It is not the purpose of this paper to deal with the function and origin of this type of cells. Their appear¬ ance in the postnatal stages of the rat, as recorded in table 5, agrees with what Apolant points out as the course of the develop¬ ment of the cells in the later ages of the animal. Carpenter and Conel (T4) noted this type of cells in considerable number in the rabbit, guinea-pig, muskrat, and porcupine, but rarely, if ever, did they find them in the sympathetic ganglion of the rat. As these authors’ observations were made most probably on one or on only a few stages of the rat, the small number of such cells in the entire ganglion justifies their statement, in a way but nevertheless the presence of the binuclear cells in the superior cervical sympathetic of the rat is beyond question. 296 CHI PING Incidentally, pigmented cells have been noted in the superior sympathetic ganglion of the albino rat. The cells of compara¬ tively young animals, from birth to eighty days, are entirely free from pigment. At the beginning of puberty we occasionally find pigment in one or two cells in an entire ganglion. The number of the pigmented cells tends to increase as age advances, as recorded in table 5. Some of the cells are only partly pig¬ mented; a few are completely covered with these granules, the nucleus remaining unaffected, while others are totally pigmented, including the nucleus. The pigments appear yellow brown, or, black in color, but whether this is merely a result of their relative abundance or whether there are several sorts of pigment has not been determined. The whole question of pigment in the Albino nervous system seems worthy of a special investigation. INCREASE IN THE NUMBER OF THE LARGE CELLS The increase in the number of the large cells in the ganglion during the first twenty days is an important event. This is chiefly due to the rapid increase in diameter of the young cells after ten or fifteen days of age. The large cells measure 19 to 25 ijl in diameter, and are loosely scattered and intermingled with small cells, as seen in each section. Disregarding their finer differences, such a group of cells consists of three kinds: 1. The advanced cells. During embryonic development it is known that the sympathetic trunks are formed through the migration of some cells which pass from the spinal cord along the paths of the communicating rami (Kuntz, TO). The advanced cells in the superior cervical ganglion are the forerunners of the neurones which come to this locality in “ skirmish order—much in advance of the others” and “they represent but a fraction of the final number of large cells” (Donaldson, T7). The number of these cells during the first twenty days varies from one to eight in the entire ganglion. 2. The moderately large cells. These cells constitute an intermediate group between the advanced cells and the small cells in the same ganglion during the first ten days of age. They are not different from other younger cells in general structure and SYMPATHETIC CELLS! ALBINO RAT 297 TABLE 6 Increase in number of large and advanced cells, 19 to 25 u in diameter, during the first twenty days of life. The ratios in the increase in the total number for both sexes between one day and twenty days stand at the foot of the column. Superior cervical sympathetic ganglion—albino rat SEX AGE BODY WEIGHT NUMBER OF LARGE CELLS AND OF ADVANCED CELLS days grams cf 1 5.6 188 $ 1 6.3 174 & 5 9.0 289 9 5 11.0 306 cf 11 15.0 291 9 11 14.0 301 ' cF 16 18.9 760 9 16 19.0 584 cF 20 31.7 2508 9 20 29.5 2248 Ratios: j '