If ij/'i'i' i'l ' ililff^?if'::''il! ' I 'lIlM 1 1 ' 1 (I i , I I 1^1 l, , I I 'll ' ,'li 1, i« I 1 l| I, J ' 1 f l|' ,..,.1,..- .,..,■„,.,■„,,# 1,, , Cffatnell Uniueraitg ffiihratH , Jtljata. JJem Mark BOUGHT WITH THE INCOME OF THE SAGE ENDOWMENT FUND THE GIFT OF HENRY W. SAGE 1891 Cornell University Library QL 942.M14 The growth and shedding of the antlers o 3 1924 002 910 556 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/cu31924002910556 THE GROWTH AND SHEDDING OF THE ANTLER OF THE DEER rUBLISHED BY MACLEHOSE, JACKSON S; CO., OLASOOW ^tibUshers to the ©niCfrsily MACMILLAN AND CO. LTD. LONDON New York - - The Macniillan Co. Toronto - - - TJic Macfiiillan Co. of Canada London - - • Sim^kin, 1-Ia.inilion and Co. Ca}}ibi-idgc - - Boivcs aitd Bovues Edinbiirgli • • Douglas and Foulis Sydney - ■ - Angus and Robertson i 1 THE GROWTH AND SHEDDING OF THE ANTLER OF THE DEER THE HISTOLOGICAL PHENOMENA AND THEIR RELATION TO THE GROWTH OF BONE BY WILLIAM MACEWEN, F.R.S. GLASGOW MACLEHOSE, JACKSON & CO. PUBLISHERS TO THE UNIVERSITY 1920 GLASGOW : l-'KINTED AT THE UNTVERSITV FRKSS IIV KUHERT MACLEHOSE AND CO. LTD. PREFACE Material for this investigation has been obtained from various sources. One of the earliest contributions was from the Duke of Montrose in the shape of a fine head of the Fallow Deer which was shot by his Grace and forwarded immediately, so that it was received in excellent condition. The vessels of the head and neck of this specimen were immediately injected so that the relations of the blood vessels of the skull to those of the antler and the velvet could be traced. Through the medium of my friend, Mr. 0. E. Philippi, several hne heads were obtained, presenting the sprouting antler in various stages of growth. These comprised specimens of the Red Deer from Gaick Forest sent by Mr. Hargreaves and specimens of Fallow Dear sent by Lord Devon. The Duke of Richmond and Gordon gave permission to examine the great and beautiful collection of deer skulls and antlers at Gordon Castle and also to photograph any specimens of service. Several of these showing the result of injury to the pedicle and its effect upon the antler were photographed and appear in this volume. My friend, Mr. Henry Evans of Jura, was good enough to give me numerous examples of the Cromie antlers, two of which are here illustrated. To all these gentlemen the thanks of the author is due for the contributions so generously given. vi PREFACE He has also to thank Dr. Shaw for contributing specimens illustrative of the histological phenomena of the growing epiphysis of the human foetus and those of children at birth which were prepared in the Surgical Laboratory of the University. Dr. J. A. C. Macewen for aid in the collateral investigation of growth of bone in fractures and valuable work in the general investigation, Dr. MacMurray for making several histological dramngs from slides illustrative of nuclear budding as seen in the antler of the deer and in the growing bones of other animals, and Miss Macewen for much aid in preparing these pages for the press and for work connected with the investigation generally. CONTENTS CHAPTER I I'A'.ES Deer's antler a deciduous structure — Preparation in skull and pedicle for growth of new antler — Xew growth springs from whole surface of pedicle — Analogy to conical stump after amputation in child's femur or humerus — Xew pabulum quickly becoming cartilaginous and ossifying centrifugally — Cap of rejuvenating cartilage — Analogy to diaphyseal cartilaginous plate — ( Irowth of cuticnlar covering (velvet) — Blood vessels of the velvet — their growth and obliteration — The histological development of the velvet — Sections of antler about to shed — Growth of hair — Nerves of antler — Effect of injury and disease of pedicle and skull (ossifymg centres) on gro-wth of antlers — Cromie antlers — views as to their causation — llacroscopic a])pearance of growing antlers — The shedding of the antler - ----- 1-32 CHAPTER II The evolution of tlie osteoblast in the antler of the Deer : Its embry- onic formation — Analogy to same formation in dog's bone — glass tube experiments — human growth and regeneration of Ijone — The typical form of the mature osteoblast — The osteoblast embeddmg itself m ossein — Osteoblast may free itself from the surrounding ossein — Osteoblasts may evolve into bone in either of two ways: (1) By direct bone formation: (2) Indirectly by passmg through an intermediary cartilaginous-stage before formuig bone — (1) Direct bone formation; (2) Indirect transi- tion into bone through cartilage — Changes in the cartilage capsules during evolution into bone : (a) The capsule becomes thmned and ragged and osteolilasts become free ; (h) Capsules become thicker and flattened mto matrix — The deposit of ossein round osteoblasts and in matrix — Osteoblast assumes the role of bone cell — Osteoblasts pavement trabeculae — Ossification advancing centripetally and centrifugally — Blood vessels in relation to osteoblastic bone formations : ( 1 ) Part played by blood in the evolution of bone ; (2) The obliteration of vessels by centripetal osseous deposit — The osteoblasts do not grow from the blood vessels -------- 33-81 CONTENTS t;HAPTEE in The blood supplies of the antler and the effect of their arrest^ — The process of separation of the antler — Preparation for shedding appears at the birtli of the new antler and increases during its vigorous growth — Process commences at level of corona — Obliteration of superficial vessels at corona — Corona presses through cutis and superficial vascular supply is cut off — Osseous tissue in antler becomes avascular and dies — the changes in the vessels — The separation of the dead antler by means of intensified action of the living tissue in pedicle — The production of granulation tissue hi pedicle — The shedding of the antler is an aseptic process occurring in the open air - - 82-89 CHAPTER IV Nuclear budding occurring in osteoblasts in developing antlers — As seen occasionally inside of cartilage envelope — Much more frequently in free osteoblasts — Many cells in all stages of growth seen near the cells exhibiting nuclear budding — Daughter cells — Giant and multiple cells ; their formation — Castration, its effect upon nuclear budding — Nuclear budding of same kind may be seen in epiphysis of dog and in human epiphyses and in pathological products — Notes on chromidiosis from Howard and Hertwig — The effect of castration on the growth of the antlers .--.... 00- 105 LIST OF ILLUSTRATIONS PAiiK 1. Head and antlers of Wapiti — Cervus Canadensis - ■ - 4 2. Head and antlers of Moose (elk) — Aloes Machlis - - - 5 3. Head of red deer (cervus elaphus) — sprouting antlers - - 7 4. Red deer (cervus elapluis) — s])routing antler in section - - i> 5. Red deer (cervus elapluis) — siirouting antler in section - - 11 6. Head of fallow deer (cervus daraa) — sprouting antlers - - 12 7. Head of fallow deer (cervus dama) — sprouting antlers - - ]:> 8. Fallow deer (cervus dama) — pedicle, portion of liasc of antler, and skull in section - - - - - - - 14 9. Red deer (cervus elaphus) — section of antler about to shed - lO 10. Red deer (cervus elaphus) — section of antler about to shed - 17 11-18. (Aitaneous structures covering the antler (vi-l vet) - - l'.)-22 19. Skull and antlers of red deer — cervus elaphus - - - - 24 20. Skull and antler of red deer — cervus elaphus — jiathological - 2."i 21. Antler — red deer — pathological ------ 20 22-23. Red deer — cromie antlers ------- 3()-3] 24-37. Evolution of osteoblast ------- 37-4:; 38-43. Sections from dog's epiphysis near junction with diaphysis — for comparison --------- 44-4(> 44-.57. Direct transition of osteoblasts into bone - - - - 52-58 58-68. Evolution of bone through cartilage (indirect bone forma- tion) ----------- 60-65 69-85. Evolution of bone through cartilage (indirect bone forma- tion) - ----- 66-75 86-89. Evolution of bone through cartilage (indirect l.ione forma- tion) — vascularisation of cartilage ----- 78-79 X LIST OF ILLUSTRATIONS PAOE S9a. Section of antler about to shed ------ 84 90. Shed (dead) antler --------- 88 91-93. Preparation in pedicle for sprouting antlei' - - - - 88-89 94-104. Nuclear budding ..----.- 93-98 10.5-107. Giant cells, compound cells ----- -99-100 108-109. Process of repair in human tibia after acute o.steomyelitis (for comparison) — giant cells ------ 100-1 i I \] INTRODUCTION The inquiry into the phenomena connected with the growth and shedding of the deciduous antler of the deer was undertaken to determine the data of a very inter- esting phase of nature which liad not l)een ah-eadv investigated, was imperfectly imderstood and which, on its own merits, was of intrinsic value. From the data thus obtained any differences which might be fomid between the development of bone in the antler and that of the ordinary production of osseous tissue would be noted and it was hoped that light might therebv be thrown on osseous development, in other parts of the animal economy. It has proved to be of service in both these respects. The growth of the velvet is very interesting in itself, as it is an instance of the complete reproduction of the whole of the cuticular elements of the skin, — stratum luciduni, stratum Malpighi, hairs, hair follicles and glands, — which all grow with remarkable rapidity, keeping pace with the growth of bone and covering, it may l^e, an enormous palmate antler within three months. Apart from embryonal evolution, such an extensive growth of all the elements of the skin does not occur in the reproduction of any other part of the animal kingdom. Although the analogy may not be strictly correct, it is nearer to what occurs in the reproduction of the digits of the newt or the tail of xii INTRODUCTION certain lizards after their removal, than to any pheno- mena seen in mammalian repair of tissue after surface wounds. In the latter, in man the cuticular elements are imperfectly reproduced^ the stratum lucidum and stratum Malpighi alone appearing, glands and hair follicles being absent. In many parts of the antler, especially toward the terminal point of the tine, the cutis (stratum Malpighi) grows directly on bone without the interposition of any membrane. In this respect it resembles the manner in which the cuticular covering is seen to adhere directly to human bones (where the bone is superficial), after the healing of some compound fractures, such as in the tibia, and as has been many times seen — during the late war — on stumps after amputation where the cutis has become directly adherent to the bone. The vessels of the velvet grow with equal rapidity, supplying abundant pabulum for the growth of the velvet and maintaining at the same time the temperature of the growing bone within the hairy covering. What- ever may be the case in the early stages of the sprouting antler, these cuticular vessels do not inosculate to any appreciable extent with those of the underlying bone. The osseous growth in the antler is derived from pre- existing bone in the skull, a pedicle projecting from the frontal bone from which the antler springs. The nearest analogy to this is epiphyseal growth of the diaphysis of the long bones, the distal epiphysis ever being borne further away from the proximal, as it deposits its osseous framework. Ample opportunity is afforded of studying the development of the osteoblasts and the deposition of ossein among the millions of cells that spring originally from that base. The rapidity of growth is so great that all phases INTRODUCTION xiii of l^one development may be found occurring simul- taneously, in one part or other, of a half grown antler. The phenomena elicited at the earlier stages of develop- ment are in the main analogous to those of the growth of bone in other parts of the mammalian skeleton. From the very inception of the antler growth, however, arrangements have been made for the rapid shedding of the antler, after it has performed its evanescent purpose. This is effected by excessive osteoblastic formation and the deposition of ossein, constricting the calibre of the internal vessels, resulting in eburnation and ultimate ischemic necrosis, the shedding of the antler ultimately occurring from the action of the living tissue on the proximal side in the pedicle. '_ Provision for the ultimate shedding of the velvet is similarly arranged for at the inception of the new antler. The abundant ossilic pal)ulum issuing from the pedicle overflows and overlaps the pedicle circuni- ferentially forming the coroiui. This may be seen in the sj^routing antler illustrated in Figs. 4 and 5, which photographs are taken from a specimen two weeks after shedding. From that period the corona continues to grow, and it may be seen in nuich more pronounced form in Fig. 8 representing the corona at eight weeks. The large blood-vessels of the velvet which supply both pabulum and heat are at first protected by lying in grooves in the antler and in the ossific matter of the corona, but ultimately the ossification occurs at the corona so quickly that it encroaches on the lumen of the vessels and subsequently obliterates them. It is to be noted that the facts adduced here are contrary to the prevalent belief that the corona appears only toward the terminal portion of the growth of the antler. It is interesting to see that nature has at the xiv INTRODUCTION very inception of the growth provided for the fall of this deciduous structure. The energizing entity and determining factor acting under hereditary law, is the osteoblast which is evolved from pre-existing bone cells or osteoblasts in the pedicle. Its evolution may be traced from its syncitium through its various stages until it assumes its mature form which is typical. This typical cell, when first seen in the antler, was supposed to be peculiar to the antler of the deer, but it has been found on further search to be identical in shape with the mature osteoblast seen in other forms of osseous development, though in the latter the typical forms are not seen in such abundance as in the antler, and often in order to be observed must be looked for carefully, as synchronously with the assumption of the mature form, the deposit of ossein occurs so quickly that the outline of the cells becomes obscured. The recognition of a typical form of osteoblast enables one to trace this energizing agency through direct and indirect transformation, and the view of ossification is thereby more easily understood and simplified. The rapidity of production of the mass of ossification in the antler requires some explanation other than could be accounted for by normal cell division, and the pheno- mena of nuclear budding which is seen in the antler may be interpreted as an adjunct to the ordinary methods of cellular multiplication. That such a view is heterodox does not necessarily exclude its consideration, and the fact that a someAvhat similar process to nuclear budding in the antler is seen in rapidly growing tumours, such as the sarcomata, lends colour to the view. The antler is the most characteristic feature of the deer tribe (cervidae). It is a word derived from the mTRODUCTION xv French antoilUer, a derivative from the corrupt Latin anteoculareni — which originally was applied to the brow tine. This word antler distinguishes these cranial for- mations from the sheath covered horns of the Bovidae.^ Some species of existing deer are antlerless — Chinese water deer and the musks- -and others possess permanent antlers which are not deciduous, the velvet remaining in the latter throughout the life of the animal. Some extinct ruminants, probably allied to the giraffes, have branching bony appendages springing from the skull much like that of the present day deer, except that the antlers are permanent. The males of all the other existing cervidae are adorned with antlers, the females being antlerless. In the Reindeer species, however, both sexes have antlers. The amount of l)ony matter annually secreted to form antlers of the larger deer is enormous, antlers of the Red Deer having been obtained which weigh up- wards of 74 lbs. while those of the extinct Irish deer must have probably scaled 100 lbs. during life.^ " In weight the Elk will scale from 900 to 1400 pounds and the antler may weigh as much as 60 pounds. The largest span of an Elk antler on record is in possession of the Duke of Westminster. It measures six feet one and one quarter inch." ^ It has been the custom to regard antlers as dead structures incapable of repair after injury and to look upon the pedicles as consisting generally of such solid ivory like bone that they could not transmit blood to the ■" core " of the antler, and therefore that they could not play a part in the reconstruction of a new antler. Such views, stated in that broad way, are not borne 1 The Royal Xutund Histury, vol. ii., Lj-dekker, F.E.S, London, Fred. Warne & Co. 1894. xvi INTRODUCTION out by the facts recorded in this volume. There is a period doubtless in which the antler is dead, and its shedding is due to its having become a necrosed struc- ture. Prior to that, however, the antler is full of life and capable of repair after injury. The antler is capable of reconstruction during the growing period and the pedicle is then full of blood, which it transmits to the interior of the antler. The pedicle participates actively in the shedding of the necrosed antler and therefore at all times it must be in active life and nutritional condition. In making deductions from the Genus Cervus it may be as well to remember that none of this family have a gall bladder (which all Bovidae have). The histological data given in these pages were obtained from the heads of various varieties of deer, the red deer {cervus ela/phus) and the fallow deer {cervus dama) chiefly. The roe deer {capreolus) though fre- quently examined, — and some of the sections of the antlers are included — did not present any advantage over the larger varieties. The antler of the roe deer owing probably to its smaller size did not show the exuberance of growth of the larger varieties. The heads of deer were obtained from many sources and include specimens of the sprouting antlers, two, four, five and eight weeks after the shedding of the old antlers. Macroscopic illus- trations of a few typical specimens are given, and sections of several of these are also included from which the naked eye appearance of the raj)idly growing bone and cartilage may be seen. The statement is made in the beginning of this volume that the weight of the antler in " the larger species (such as the Irish Elk) is more than that of all the bones INTRODUCTION xvii of the skeleton put together," and this has been quoted from the Study of Mmnmals, 1891, on the authority of a careful observer. Sir William Flower. This is a very graphic statement, and brings forcibly before the mind of the reader the enormous osseous development of the antler. Sir William Flower has not, however, given any data as to whether he has arrived at that conclusion by actual weighing of the specimens. TH]] (iliOAVTH OF ANTLERS CHAPTER I Deer's antler a deciduous .structure. Preparation in skull and pedicle for gro^\th of nc^r antler. New growth springs from whole surface of pedicle. Analogy to conical stump after amputation in child's femur or humerus. New pabulum cjuickly becoming cartilaginous and ossifving ci-ntri- fugally. Caji of rejuvenating cartilage. Analogy to diaphj'seal cartilaginous plate. Growth of cuticular covering (velvet). Blood vessels of the velvet — their growth ;iiid nblitcration. The histological development of the velvet. .Sections of antler about to shed. Growth of hair. Nerves of antler. Effect of injury and disease of i)edicle and skull (ossifying centres) on growth of antlers. Gromie antlers — vie^vs as to thcii' causation. JNIacroscopic appearance of gro"wing antlers. The shedding of the antler. Deers antler a deciduoKS structure. When it is reineiiibeied that the deer".s antler is deciditotfs, a new ofie being formed every year, that the eiiornioiis growth of boiie forniitig the antler is prodnced in three or four months, and that the weight of the antler in the hirger species is said to be more ^ than that of all the bones of the skeleton jjut together, ' Sir Wm. Flower, Slurh/ of Mo inmul^, 1891. G.A. A 2 THR GROWTH OF ANTLERS it is all the more striking that this growth of the antler proceeds from a single comparatively small centre of ossification situated in the frontal bone. The regenera- tion of the myriads of cells and the rapidity of cellular proliferation necessary for the growth of the antler is much greater than that which obtains in any other normal process of single bone formation within the deer or other animal. When the osteoblasts have reached maturity they extract from the blood the bone-making salts and deposit them so that the cells become imbedded and immured. In this way the fabric of the antler is built. No colony of coral insects is more replete with active life. Pathological conditions such as fractures of bones exposed to great continuous movement may show rapid and excessive osseous development, but never to the same extent or produced with the same rapidity as that of the antlers. The rapidity of gro^i^h in the antler is comparable with, but in excess of, that of the most rapidly produced tumours. In the first year of a buck an outgrowth or exostosis , rises from the frontal bone which, when the outgr'o-wth is completed, forms the pedicle. The pedicle not only springs from the frontal bone of the skull, but it is identical vnth it in strTicture, showing Haversian canals and having the same blood supply. The pedicle at the beginning of the growing period is highly vascular and pulpy, and is covered with cartilage which ossifies from the base upwards, and as ossification proceeds the cartilage continues to grow in advance until its full size is reached, when its ossification becomes completed. The pedicle once formed is a permanent structure growing in circumference during subsequent years. It is from the distal extremity of the pedicle that the antler springs, and when the aiitler is shed its shedding DEKRS AXTLER A DE(.'IJ)UOUS STItUC'TURE 3 takes place at the same point. The antler appears during the secoiid year of the animal's life, when it presents only a single stem. Each succeeding year the new antler shows a new tine or branch until maturity is reached, after which the growth becomes irregular. Tliese two specimens (Figs. 1 and 2) are presented as illustrati^'e of the great development (if bone in the antlers of the larger deer. The one is tlie head and antlers of the Moose or Elk, the Akes jiiarlilis. which was shot in the north of Canada. The other is the head and antlers of the Wapiti — Ccynis ('(Dxidcnsis- from the same region. In both, the development of lioiie. wliidi takes place in three months, is enormous, and as tlie antlers ai'e deciduous, it occurs vearlv.^ 'Sir William Flowei'. in tlio introchictiou to the Slinlii of Muiiiiiinls. 18!)l, observed the j^niwtli of the antler of the red deer as follows : "On Mareh 12tli, tlie antler was shed. On Maroli 2.3th (thirteen days after), a i^rowth aijout the sixe of the red deer s]ieeimen hgured in thi.s vohune ( Fii;-. .'i . Sj.rontini; antlers, p. 7. On April '.)th (29 days after), the growth was aliont the size of the fallow deer specimen figured in this volume (Fig. (ij. Sprouting antlers, p. 12. On May ISth (.39 days after), the growth was about the size of first falloH deer specimen in author's collection ( l'"ig. 7. p. I'!). On .Tune 27tli (79 days after), antler complete Imt -with velvet still intact. On .luly 2(lth (i02 days after), shedding of velvet advanced. On October ist (175 days after), hard bone. The growth may be said to be completed on .Tune 27th. that is. 79 days after shedding of the antler. In red deer ((_'erriix elaphiis) the antler is shed between the end of February and early |)art of A|>ril. The older animals shed their antlers earlier than the young. The number of points on the antler increases with the age of the animal. When there are twelve points ])resent it is known as a Royal Stag." " Even the great horn of the Wapiti (Fig. 1 ) and juilL'ing from analogy those of the Irish Elk — a pair of horns which weigh 7(1 lbs.. — more than all the bones of the skeleton put together ? — are i)roduced in course of 3 or -t months." Sir AVilliam Flower. The mark of interrogation does not appear in the original. HEAT) AND ANTLERS OF WAPITI— CERVUS CANADENSIS. Fig. ]. Aiitli^rs showing great development of hone. Author'.s ColjjKction. HEAD AND ANTLEE8 OF MOOSE (ELK)— ALCES MACHLIS. Fig. Antler.s showing great Jevelopment of bone. Author's Collectkin. 6 THE GROWTH OF ANTLERS Preparation in skull and pedicle for growth of new antler. When a new ajitler is about to form, the whole thick- ness of the skull from the brain cavity outwards, through the pedicle, exhibits greatly increased vascularity com- pared with the same parts when the growth of the antler has been completed. The blood supply of the pedicle comes from the vessels of the skull and frontal bone. The pedicle is highly vascular, especially toward the centre from which active osseous proliferation is pro- ceeding — from the centre outwards toward the cir- cumference. The new growth pours out from the whole interior of the pedicle and overlaps it circumferentially, laying thereby the foundation of the future corona (Figs. 3, 4 and 6). New growth springs from whole surface of pedicle. Whenever the antler is shed, the pent up forces which had been accunmlating preparatory to the new growth find vent and from the whole upper surface of the pedicle a mass of new formation springs and overflows its edges — in form like a young mushroom projecting from its stalk. It is to be noted that the distal surface of the pedicle where it abuts on the ajitler, before the shedding of the latter, presents a concavity, and immediately after the antler is shed a convex shape is assmiied, from which the new tissue forms in the same place (Figs. 9 and 10). In respect of this overlapping of the pedicle, it resem- bles the form of growth which sometimes covers the end of the human femur and humerus after amputation, through their shafts — instead of remaining a plain sawn surface, the cut shaft often becomes covered with a cone-shaped cap of new bone, which overlaps the periphery of the shaft. SPROUTIXG AXTLERS Fi., HEAD OF RED DEER (OERVUS ELAPHUS)— SPROUTING ANTLERS Head of Red Deer (Ccn-u.^ ehipfitti:) sent from <.;aiek Forest bv 5Ir. Hartzreaves throiish Mr, Philippi, May 1913. Antlers have been shed about two weeks previously, and three inclies partly pedicle partly new antler is seen projeitini: from the sliull. (Deseription on pp, 28 and 29.) 8 THE GROWTH OF ANTLERS Analogy to conical stump in children. The growth of the antler is in some respects hke the growth of })one which follows amputation through the axm or thigh of a child, forming ultimately a conical stump. The reason for this is that the humerus and femur continue to grow in length fronr the proximal epiphysis while the soft tissues recede, pressure being exerted on them from within by the constantly growing bone which fiirally protrudes through them, it being then covered only by a single layer of epithelium which is thinned toward the extremity, so that finally a pellicle of stratum lucidum alone remains, which proliferates quickly in an attempt to keep pace with the growing bone, which it covers. In the antler, however, the whole of the epithelial layers grow with great rapidity, keeping pace with the osseous growth, clothing the whole structure. New fuhvlum quicliy becomes cartilaginous and ossifies centrifugally. Thus it is seen that the new antler springs from the pre-existing bone in the pedicle and skull, both of which become highly vascular preparatory to fresh ossific effort. The pabulum thus produced is thrown out from the pedicle and quickly assumes a cartilaginous form, which speedily ossifies from the centre outwards (Figs. 4 and 5). Cap of rejuvenating cartilage. As the antler grows it is preceded by a mass of rejuve- nating cartilage which forms a cap over the extremity of the advancing bone (Fig. 4). This cartilage is in a state of active proliferation, at the same time SECTION OF SPROUTING ANTJ.ER Fi.;. 4, RED DEER (CERATS ELAPHUS)— SPROUTING ANTLER IN SECTION Appfurauc^' ot i^fdiele and ntw antler about two weeks after shedilinc. Eed Iteer skull, pediele and sprouting antler all in section, showing cartilaginous new fonuation ossifying in centre from junction witll pedicle. 10 THl-: GROWTH OF ANTLERS reproducing itself distally while proximally it is being converted into the bone formation of the antler. Analoi/y to diapJii/seal cartilaginous plate. It somewhat resembles a distal " diaphyseal " car- tilaginous plate, inasnuich as, the more it contributes to the growth of l^one, the farther it is borjie away from the centre by the osseous deposit which it has so freely furnished. There is aii analog)'' also to certain forms of exostosis which grow in ossifying cartilage — the cartilage always preceding, the bone until the full growth has been attained. The cutis coverin;/ the antler (relvet). The thick cutis covering the skull stops at the ex- tremity of the pedicle, from which poiiit a thin layer of cutis spreads with great rapidity over the bone and cartilage of the antler and keeps pace with the subsecpient growth of the latter. Similarly, the dense coarse hair covering the forehead of the deer is not contiimed further than the distal aspect of the j^edicle and fi'om that point forward there is a growth of fine hair — at first verv fine and soft but afterwards stronger, though always much more delicate in structure than the hair on the proxinral side of the corona (Figs. 4, 5 and (i). J^uring the process of shedding of the antler, the cutis may be seen spreading over the granulation tissue which con- stitutes the ]iew formation, and in the early days after shedding, a thin pelhcle consisting principally of the stratum lucidum covers the mass, except toward the centre where there is a bare patch of grajudation tissue which is gradually cicatrised, leaving a cicatricial mark which can be distinguished for weeks afterwards. This THE CUTIS COVERIXG THE AXTI.ER 11 cuticular pellicle is at first destitute of liaii', being quite bald, but very soon a soft do\ray liair covei's it. RED DEER (CERVUS ELAl'HUS)— SPROUTIX*^ AXTLER IX SECTIOX About twii wei'ks alter slipddiiig. Ked Deer ^kidl, peilirle and sprouting antler in ^eetion, showing vascularity oi skull and pedicle, mass vi cartilage in antler. i_>ssitii;atiun cunmieneing froTii centre near pedicle, rei)resented Ity the darker sliadtnl purtion and spreading upwards and outwards to (.-(.irona. The blood vessels of the velvet — their growth and obliteration. The cuticular covering (the velvet) is nourished by very numerous big vessels, mostly branches of the temporal artery, which run vertically on the antler and 12 THE GROWTH OF AXTLERS Fir., li. HEAD OF F.ALLOW DEER (C'ERVUs; D.\iIA)— SPROUTIXG AXTLERS About four weeks after slreddiniz. KAI.I.nW DEEtl ICKKVfs UAMaI SPROUTING ANTLKUs. Sliot by Lord Devon. Sent thriuiizli :\[r. Pliilippi. Jnne 1013. SPROUTING ANTLERS 13 Fi( HEAD OF FALLOW DEER (e'EKVUS D.\.MA)~SPROUTIXG AXTLERS Abi.iut live weeks alter sliedtling. HEAD OF FALLinV DEKR (CKKVVS IIAMA) SPKOCTIXG ANTLEH. Sent throutlll Mr. Philippi: June IS, 1913. 14 THE GROWTH OF ANTLERS Fic, 8. FALLOW DEER (CERVUS DAaLl)— PEDICLE. PORTION OF BASE OF ANTLER, AND SKULL IN SECTION SKCTIOX OF FALLOW DEKE ANTLEK, PEDICLE, AND SKULL. ANTLER 2/oRr) GKOWN. About eight weeks after Mlieildiiig. Corona well developed, cutis thinned over it. Compare thickness of cutis on pedicle with that on antler an Avhicli supplies Ijoth pabukmi and lieat. ( )sseous growths are formed by the Ijone from Avitliiii. growing outward between these A'essels so as to leave tliem partially embedded in grooves. These grooA'es or gutters leave permanent markings on the outside of the solid antler. If this osseous enci'oachment on the blood vessels were continued it would idtimately encircle aiid obliterate these vessels in tlieir whole length. l:)ut befo]'e this can occur, the vessels bv a somewhat similar process, l)ecome strangled by osseous encroachment at the corona and shriA^el oft', while the intensive bone production in the interior of the antler is lessened by osseous encroachment upon the lumen of the internal vessels througliout the antler as Avell as at its l)ase — an osseous sclerosis foi-ming. From the superficial vessels c(]iiipara.ti\('ly lew veiy fi)ie branches penetrate the deeper layers oi' the skin, and these either do not ajiastomose or thcA' do so A'ery spai'selv witli the jietAvork oi' tliiji-walled a'csscIs iji tlie interior of the bojie. The l/istolofjical di'rcJojnneyit of the relrcf. The great rapidity with wliicli the cutis gi-ows coa ering the antler and keeping pace pari passu with the osseous tissue is remarkable. It is interesting to see how com- plete the cutaneous development is. It coA'crs the whole antler from the base to the tip not only with the epithelium of the true skin, but also with its glands, hair follicles and appendages. The com2:)lete reproduction of all those cutaneous structures springs by cell proliferation from the pre- existing structures covering the pedicle, and dift'ers thus from epithelial reproductio]i covering cicatiicial tissue It) THE GROWTH OF ANTLERS ■i....:.^ ,'? RED JJEER (CERVUS ELAPHU.S)— SECTION OF ANTLER ABOUT TO SHED Authok's Collection. SECTION UKD I>EKU AXTLEH AND PORTION I CKItEBKAL CAVITY. SKULL, PEDICLK, AND Preparatory to sliediling of aiitier. Great vascularity of skull and pedicle, " line of demarcation " beginning to form between dead bong aild living at convexity of antler near corona. The skull and pedicle are hypervascular preparatory to new growth. The antler presents its white convexity towards the pedicle. After the shedding the pedicle assumes a convexity upwards. ANTLER ABOUT TO SHED 17 Fig. 10. RED DEER (CERVXTS ELAPHU.S)— SECTIOX OF ANTLER ABOUT TO SHED Author's CoLLf:cTio>'. A stage toward the shedding ol antler. Section thronsh skull, pedicle, and base oi antler. Autler is now dead Ixine with coagulated disintegratint: blood in it. The sknll and pedicle are very vascular in preparation for shedding and regeneration of new hone. The portion of tlie antler ahutting on the iiedicle consists of dense white hone, presenting a convexity toward the pedicle. ,18 GROWTH OF ANTLERS of a wound where the epithehum, stratum lucidum and stratum granulosum are the only elements reproduced and not the glands or hair follicles or hair. It is noted that the stratum lucidum precedes the stratum granu- losum in covering the antler, though both are developed quickly. The pulpy mass of embryonic osseous tissue springing from the pedicle immediately after shedding of the antler is seen to be already partially covered vnth stratum lucidum. One sees in Figs. 1 1 and 12 that the development of the superficial cells — ^the stratum lucidum — is in advance of those of the stratum granulosum, the former being well developed while the latter are still embryonic. This is the same as is seen in the covering of aseptic wounds in man — ^the stratum lucidum is the first to cover the wound and it is followed by the stratum granulosum. In wounds healing after a broad covering of granulation tissue healing from below upwards, the stratum granulosum may be the first to cover the wound. The dermal structures seen in Fig. 11, one resting upon the embryonal osseous tissue — there being no intervening membrane. The nerves of the antler. Branches of the trigeminal nerve ascend in the cuti- cular covering in line with the blood vessels and supply the acute sensitivity of the velvet — which' thus protects the growing antler during its softened state when it otherwise would be liable to injury from contact with external ol)jects. This would be more especially necessary with adult animals which had been in the habit of Using the hardened antlers freely. The nerve supply in the interior of the antler in the midst of the CUTANEOUS STRUCTURES COVERING THE ANTLER (VELVET) Fig. 11. SECTION 2S1. — FALLOW DEER ANTLER, 2/3rI) GROWTH, SECTION NEAR TIP. i mm. 4 eye-piece. Cutaneous structure — stratuni Malpiglii and stratum luciduru superimposed on embryonal osteoblastic tissue. Fig. 1-2. section 424.— fallow deer. 4 mm. 2 eye-piece. Stratum lucidum well developed ; stratum Malpishi still in embryunic state. CUTANEOUS STRUCTURES (VELVET) SECTION 425. — FALLOW DEKR. 4 mm. 2 eye-piece. Stratum lucidum well developed ; atrutuiii Malpi^dii still embryonic and ill defined. .-.v^'!^V»jP;>«H,-.. II,- -: \ (., iA- ■ . ■»-v"^«^^p»" - c.'-- •** *^ - — — >^^ Fii;. 14. SECTION 47n. — FALLOW DKEE, 2/3R11 GROWN, IJ" FKOJl TIP. Three huir i:tulhs in section. CUTANEOUS STRUCTUKES (VELVET) <\»'K ^^ ^' V^ Kic. ir,. ■.■^■^(■i * "--'«' Fic;. 10. SKCTION 47'.l. — I''AI.I.I>W IlKER ANTI.KIL, IfMlW URuWTH, 4 mill. 4 uye-piecf. Ciitiineoiis uIiiik] in sri'timi. 1 .'," KHOM TIP. CUTANEOUS STRUCTURES (VELVET) Fk;. 17. section of skin (velvet) anll hair bulb with glands. low poweb. i Fig. 18. section 424. ^fallow deek. 4 mm. 2 eye-piece. Hair bulb in longitudinal section. THE XERVES OF THE AXTLER 23 osseous matter is very difficult to trace during the period of rapid osseous deposition. Effect of injury or disease to -pedicle or shdl {ossifying centres) on growth of antlers. Wlien the pedicle or skull from which it springs is injured or altered by pathological processes, the antler is directly affected thereby. Thus a bullet j^assed through the right pedicle of an antler of the Red Deer at its junction with the skull, a groove being formed in the latter while the pedicle was thrown outwards and downwards, in which position it still adhered by an osseous attachment to the skull. The growth from the injured pedicle resulted in a deformed left antler dwarfed to a fourth of the size of its neighbour. In another instance a ludlet struck the left pedicle, penetrating its outer aspect near the corona, without damaging the base of the pedicle. This disturbed the relation of the component parts in the growing centre and deflected the growtu of the subsecjuent antlei's springing from that point. Though the antler on that side was irregular in form, being divided iiito two, one part having a very long basal hiie in front, and though it was shorter than its neighbour, yet the whole amount of the ossitic matter produced was not lessened by more than a third of that of the normal (Fig. 19). On the other hand, when a pyogenic process has affected the base of the pedicle and adjacent skull, the growth may be entirely destroyed and the portion of the antler which existed at the time of the pyogenic invasion mav be entirely shed or retained by skin onlv — falling flail-like over the eye on the same side. In such a case no fresh antler can grow as the ossifying 24 THE GROWTH OF ANTLERS Fic. 19. hkull anil antlers ok kei> dekk— cervus elaphus. defnhmkil and iiwakfeo right antlke. result of injury to pedicle. From Collection' of Duke of Richmond and Gordon. Defonueil and duarleil riulit antler I'roiii bullet iieiietratiiig outer side of pedicle- near corona. PATHOLOGICAI. CONDITIOXS AFFECTIXG PEDICLE 25 centre has been destroyed. The pedicle of the neigh- bouring antler being unaffected, the antler grows to its normal dimensions. See Fig. 20. NKULL AMI .V.NTLEi; I1F KKil DKEK— CKKVIS ELAPHUS — I'.VTHI ILOGICAL. The right side sliowing osteomyeUtis affecting skull and pedicle ^"ith consequent stunted antler. The pedicle and antler are in one piece, the pedicle having separated from the skull. It was attached by skin <.inly and swayed to and fro mth the movements of the animal. Fk05I COLI.ECTIIIN OF AtTHOR. Tlie antler itself is liable to injury especially in its early life. The abmidant supply of sensory nerves to the velvet of the growing; antler makes the animal 20 THE GROWTH OF AXTLERS careful in using tlie antler or bringing it into violent contact with external objects. Occasionally, however, accidents happen, as is seen in the twisted antler shown in Fig. 21, which was the result of an injury to the RED DEER (CERVUS ELAPHUS)— (iliEEXSTICK FRACTURE OF ANTLER. Fi(i. 21. ANTI.KU — null IlKKIt -PATHOl.OUlC.Mj. Greenst.ick fracture, result of injury diirint.' t^rowin^ period, and subsequent tllickening fif bone at point of damage. From Chli.kci'kin ok Autiidk. growing antler, producing a " greenstick fracture " which has firmly united in its deformed position. Not having been set when still soft, it has become consolidated in the twisted position. cro:mie antlers 27 Cromie antlers — vieics as to their causation. The Cromie Antlers are found not infrequently in Jura Forest. All the specimens in Author's collection have come from there. Some writers favour the view that they are illustrative of atavism from an odd species of deer now extinct, the strain only showing occasionally. It cannot be due to a general malnutrition, as many of the animals with cromie antlers attain a good size and weigh heavy. In-breeding is said to be a cause, but this cannot be the whole cause, as in some isolated forests where in-breeding has occurred cromie antlers have not resulted. Whatever may be the true cause, the pedicles are, usually, smaller than normal both in length and circumference. The foi'm assumed by the antler is somewhat similar to that assumed ]>y antlers whose ossifying centres have been impaired : — a rickets of the antler ; — or where the incentive to the production of bone in the antler has been diminished. There is no indication of malformation in any of the other bones of the skeleton. In this respect, observation on the condition of the testicles in the cromie would Ije of a alue not only as to whether they are noiinal in form, but whether they functionate properly. In one instance a cromie was found to have unde- scended testicles, though it does not necessarily follow that they were defective in function. The arrest of groAvth of the Ijone in the antler due to castration, and the deformity and stunting which occurs in other cases where the testicles have been injured, make it desirable that inquiry should be made in that direction for the elucidation of the subject. Castrated animals fatten much more quickly than normal ones, and cromies usually are heav}^ and fat. Data as to their procreatiA'e power would be of value. 28 THE GROWTH OF ANTLERS Macroscopic appearance of specimen of antlers commencing to f/miv — about tiro ireels f/rowth after shedding (Figs. 3, 4 and 5). On the head in front of the ears, a couple of dark knobs presented, bearing near the centre of the apex of each, a slightly depressed reddish-white mark doubtless cicatricial in character due to the final stage of shedding of the antler. These two knobs somewhat resembled two large ripe dark figs, from which the flower had separated. They were still soft superficially, the right bearing an indentation from external pressure. The kernel within conveyed to the touch the impression of yielding cartilage. The stout, vigorous hairs of the skin covering the skull and pedicle stopped at the junction of the pedicle with the new growth. Toward the base of the sprouting antler very fine hairs were seen, on the upper part they were scarcely visible and there were spaces toward the apex of the antler where there was no visible appearance of hair. The cutis was very thin over the new gro\\'th and especially over the top. (Like a conical human stump, the cutis covering the bone being very thin — stratum lucidum.) A longitudinal section was made through the sprouting antler, pedicle and skull of the specimen of Red Deer presenting the appearance shown in Figs. 4 and 5. The measurements of the specimen were, in longi- tudinal direction : 1 . From the inside of the skull — brain cavity to tip of sprouting antler 3 iV inches. 2. From indication of corona to tip of sprouting antler IVu ,, 3. From V shape in centre of pedicle to tip of sprouting antler 2i'u ,, MACROSCOPIC APPEARANCE 29 So that the actual height of tlie rudimentary antler was nearly two inches. The measurements of the diameter through the pedicle compared with that of the rudimentary antler were : Diameter of pedicle Diameter of rudimentary antler In the reverse direction : ItV inches. IrV ?? 2iV inches. 2tV 3? Diajneter of pedicle Rudimentary antler This showed that the two diameters of the rudimentary antler was greater by three-tenths in one direction and four-tenths in the other, than the pedicle from which the new growth sprang. Thus the new growth had overflowed or overlapped tlie pedicle. The whole bone from the interior of the skull through the pedicle upwards is mucli more vascular tliaji the same parts when the growth has stopped. The great mass of the new gro^vtJ^ is cartiLiginous and soft. At the darker part in the centre where it joins the ]_)edicle — the ajjex of the V seen in the specimen — new l)one is groAving from the centre, while the edges and circum- ference are still cartilaginous and the skin very thin over the cartilage. Fine hairs are also seen sprouting from the new skin. The two heads (Figures 6 and 7) were those of Fallowdeer, the sprouting antlers showii being four and five weeks respectively after shedding. They were good specimens received in very fresh condition, and from which many valuable sections were obtained. 30 THE GROWTH OF ANTl.KRS Macroscopic appearance of sprouting antlers. The liistological data were obtained from the heads of various varieties of deer, the red deer (Certnis elaphus) and the fallow deer {Cervus dama) chiefly. The roe deer RED DEER— ABNORMAL ANTLERS Fig. 22. kki) dkkk — ckomik an'tlkhs. Presented by the late Mr. Henry Evans, shootinp tcniint, .Turn. Authok'.s Coixkction. (Capriolus), though frequently examined, — and some of the sections of the antlers are included, — did not present any advantage over the larger varieties. "J^he antler of the roe deer, owing probably to its smaller size, did not show the exuberance of growth of the larger varieties. MACROSCOPIC APPEARANCE 31 The heads of deer were obtained from many sources and include specimens of the sprouting antlers, two (Fig. 3). RED DEER— ABX0E3LAL AXTLERS Fio. 23. BED IjEEK — f EOMIE AXTLEHS. Presented by the late ilr. Henn" Evan-, =liixiting tenant, .Jura. ATTHOR'-; COLLEf TI'I-V. four (Fig. 6). five (Fig. 7), and eight (Fig. 8) weeks after the .shedding of the old antlers. 3Iacroscopic views of a few t\'pical specimens are given and sections of several a2 THE GROWTH OF ANTLERS of these are also included (Figs. 4 and 5), from which the naked-eye appearance of the rapidly growing bone and cartilage mav be seen. The section of the base of the antler eight Aveeks old shown in Fig. 8 presents a mass of well grown bone already presenting greater density at the coronal line than that on the proximal and distal side of that Ime where the bone is still very vascula,r. It is at this line that the separation of the antler from the pedicle will ultimately take place, and it does so b}" the obliteration of the blood vessels at that line within the antler and the obliteration of the cutaneous vessels by the spur of bone projecting into them from the corona without. Already the cuticular covering at the corona is thin compared with the cutis above and below that point. In the two illustrations (Figs. 9 and 10) one sees in section the base of the old antler and pedicle and skull, — the dead antler, — showing the avascular coronal line and the avascular coronal spurs bereft of cutaneous covering — that having been long shed — still adherent to the very vascidar pedicle preparing to effect the separation of the dead antler and to reproduce a fresh one. The antler presents a convexity toward the pedicle. That concavity in the pedicle will be transformed into a convexity immediately after the shedding of the antler. It is said that in castrated animals the antler presents a concavity before shedding instead of a convexity. CHAPTER II. HISTOLOGY T}ie evolution of the osteoblast in the antler of the L)eer. Its emhryonic formation. Analogy to same formation in dog's bone — glass tube expeii- ments — human growth and regeneration of bone. The typical form of the mature osteoblast. The osteoblast embedding itself in ossein. Osteoblast may free itself from the surrounding ossein. Osteoblasts may evolve into bone in either of two ways : (1) i;y direct bone formation. (2) Indirectly b_y passing through an intermediary carti- laginous-stage before forming bone. (1) IJirect bone formation. (2) Indirect transition into bone through cartilage. Changes in the cartilage capsules during evolution into bone — (a) The capsule becomes thinned and ragged and osteo- blasts become free. (6) Capsules become thicker and flattened into matrix. The deposit of ossein round osteoblasts and in matrix. Osteoblast assumes the role of bone cell. Osteoblasts pavement trabeculae. Ossification advancing centripetally and centrifugallj'. Blood vessels in relation to osteoblastic bone formations. (1) Part played by blood in the evolution of bone. (2) The obliteration of vessels bj' centrijietal osseous deposit. The osteol.)lasts do not grow from the blood vessels. Evolution of Osteoblast. Under the heading, the evohition of the osteoblast, the whole phenomena of bone formation might be described, as the osteoblast plays the principal role in 34 THE CTRO^^'TH OF ANTLERS osseous development. For convenience, however, this chapter is considered under three headings : first, the evohition of the osteoblast ; secondly, direct formation of bone ; thirdly, indirect bone formation or evolution of bone through cartilage. The histological figures represented under the heading of the evolution of the osteoblast have been chosen from sections from fallow deer antlers, but identical appear- ances are seen in the antler of the red deer and to a modified extent in those of the roe. The osteoblast — its evolution. In the earlier evolutionary stages of bone develop- ment in the antler of the deer, an embryonic mesodermic tissue of indefinite structure appears (Figs. 58, 59, 60). At parts this indefinite looking tissue may bear a resem- blance to the early stages of embryonic fibrous tissue or even occasionally to the yqxj early stages of embryonic myomatous tissue without either of these two tissues being present. In the process of evolution, from this indefinite embryonic tissue ill-defined cells at first appear, gradually assuming a more distinctive form, from which the osteoblasts ultimately emerge (Fig. 27 et seq.). Once the osteoblast assumes its mature form it becomes dis- tinctive and the cell may be easily recognised and traced through its further evolution into bone. In the antler the whole of the mesodermic embryonic layer, situated peripherally, is transformed into bone directly or indirectly, and none of it into any other tissue, such as fibrous tissue. Into bone, as it is forming, thin walled blood vessels penetrate and take with them the necessary connective tissue involved in their forma- tion. In many instances the blood spaces in the interior of the gro%ving bone are so large, the walls so thin, and THE OrtTEOBl.AST— ITS EVOLUTION 35 the periphery so crowded with osteoljlasts that it is difficult to determine the endothelial lining of the vessels. "J'he syncytium from which bone and cartilage is developed is seen to be alike in the antler of the deer — in bone gro^^^l experimentallv within glass tulies ^ — in dog's bone, in human gro\\'th, and in regeneration of bone — such as in repair after («teomvelitis and in the healing of fractures. The tyjncaJ fonii of the mature osteohlnst. The ty2:)ical form of the matui'e osteoblast is an oval cell with its nucleus situated peripherally and occupying its narrow end (Fig. 37). When the osteolilast assumes its ma^ture form, it is the immediate precursor of changes tendijig toward the formation of bone as an organised structure — such a.s the evolution of a. niatrix a,iid the deposition of ossein. Tlie deposit (.)f ossein quickly obsciu'es the osteobbist. The recognition of a definite fonn assuined bv the inature osteoblasts is advanced and is likely to be con- ceded bv those who study the histological phenomena in the deer's antler. A favoural^le opportunitA' is afforded of observing the osteoldasts in such sections, as they occur in immense numbers and are neither obsciued by too close packing — at the early stages of the develop- ment at least — nor are they burdened by obtrusive invasion of other tissues, ^^^rilst the osteoblast is still in the early enrbryonic state, its cellular form, like that of all other germinal tissues, is indefinite, but as it becomes mature it takes on the typical forms by which it is identified. Once this form is assumed, it is coinci- dent with a series of phenomena occm'ring in the cartilage ' See volume on Gronih of Bone — James MacLehose & Soils, 1912, p. 102. 36 THE GROWTH OF AXTLERS envelo^^es, the deposition of ossein and other changes which constitute Ijone as a fixed structiu'e. TJie osteo- blast is ajot to be obscured by the resultant transforma- tion of the tissue and especially by the deposition of ossein. There are, however, in the antler so many osteoblasts in a field that abundant opportunity is afforded for observing them in all stages of their evolution so that their form and development can be easily traced. After recognising this mature form of osteoblast in the deer antler, sections of growing Ijone from other animals were re-examined and found to exhibit the same typical form of mature osteoblast. This may be seen in the growing epiphysis of the dog. Figs. 38 to 43, in the gromng epiphysis and in the repair of bone in man, especially in the young adolescent. In re-examining the sections made from dog's bone growai in glass tulies recorded in a previous volume, the mature form of the osteoblast is clearly visible. So that this mature foiiii of osteoblast is not confined to the antler of the deer, but has been found in each of the species examined — though not so markedly evident in these as in the osseous development of the deer. EVOLUTIOX OF OSTEOBLAST £ «wf ^f iM^ii^S'^ i "- 'f^.|k. '• «^: v>. HKOTION 477. — FALLOW HKKR A\TLP:J[, J/oKI) CKOWTII, 2" KRitM 4 mm. 4 eye-piece. Usteijlilast^ assuiniiiy; their mature form in the iii=;ide o( rartilajz'' c l^rcparatory to bone formation, peon best in rciitre. ap.-^iil. ^ Fic. L'5. ^''■' SKCTION 47'.'- — FALLOW DEER ANTLER, 2/3RD GROWTH, 2" FRO>r TIP. 4 mm. 4 eye-piece. Osteoblasts inside cartilage capsules being surroumled and periphery im- pregnated with ossein. 38 THE GROWTH OF ANTLERS (^ % U if •? Fic. 26. SECTION 465.— FALLOW IlKKK ANTLKB, 2/3RD GEOWTH, 2" I'EOM TIP. 4 mm. 4 eye-piece. Osteoblasts assumiiis mature form inside and outside cartilage envelopes; ossein depositing in periphery of cytoplasm in cartilage envelopes. SKCTION 405. — FALLOW l.KEli, 2/:!Hh GROWTH IN ANTLKll, 2" FROM T!)'. Mini. 4 ej'e-piece. Osteoblasts assuming their mature form and free in pocket in midst of carti- lage, their cytoplasm taking on deposition of ossein. EVOLUTION OF OSTEOBLAST 39 -Sic.* « ♦•- . Fli:. 'iS. SKf'TION 477. — FALLOW DEEB ANTLER, 2/:iKII GROWTH, 2" FROM TIP. 4 nun. 4 eye-piece. Osteobl.isis forming a pocket- in the cartilage anrl assuming tlieir mature form. TJiej' are to be seen witl^in and without cartilage capsules, ossL-in being deposited in periphery of cytoplasm and matrix. . - *A» « V f ? F[(;. :29. SECTIOX 477. — FALLOW DEER ANTLEK, 2 3kD GHOWTH, 2" FK'.OT TIP. 4 miiL -4 eye-piece. OsteoVila^t.^ frt'p forming a pocket, in niid?t of tlie cartilarre. They ave ast^uriiin mature form and ossein is being deposited in their periphery. 40 THE C4R0WTH OF ANTLERS l*:v'' ^'V*- "P^ i«,. # ^ A Fig. 30. section 477.— fallow peer .vn'tler, 2/3rd growth, 2" from tip. 4 mm. 4 e^'e-piece. Osteobla.sts assuming their mature form witliin and witliout, ossein being deposited. <2S rjt. V' • ^l« §»■ Fig. 31. SECTION 471*. — FALLOW \)VA'Ai ANTLKIt, 2,oKli liUdWTH, '1" FKO>[ TIP. 4 mm. 4 uye-iiitce. Osteoblasts, havin;;; assumed thfir mature form, oonffresatinfr outsiile the cartilage roimrl a blood space, c'^sein being deposited in their periphery of the cytoplasm and in tlie cartilaue ]natnx. EVOLUTION OF OSTEOBLAST 41 Vi, *% £ *^' '#f •■# se(;tio\ 477- — fallow dekh antlkk, 2,Mki) i;iiowTH, '2" fi:'.'-\i 'I'IP. 4: nun. 4 eye-piect. Osteolilastsseeii \\'ithiii and witliout cartilage oai)snIep. Jn hntli rlie ii'Tiplirry of the C'ytO]ilasin is nnpregniitoil witli os^tT'iii as well as the surnnnKliu!.' matrix. d''-'" r* :• %0ii ■ f^^-v -" * »..?• '■" ■ ' ■•- ^%J ~- • - ^ >. • . J-. « . i^'^'^v' 'to ^^•V'-'«"V ' % ■ 4» ■ ► ^ v..%-^.* .■ ■ " '.■:*■ «.?' 5^ • ■r:'^ /.o,.,. /* 'y • ;' *; , ■ ■ ■■ '- Fic. .36. SECTION 4()1. — FALLOW 1 IKEl! .Sl'KOUTlNi: AN'TLKI;, 2" Fl'.OM TIP. 4 mm. 2 eye-piecu. Osteoblast.s which have a^sunioil their mature form, develo]iiim b'liie trn becula. SECTION 2S1. — FALLOW HEEK ANTLEK, 2 oUI) GROWTH FIIOM TINE, 4 mm. y e} e-piece. Osteoblasts, withtlrawn from osseous trabecula by the shrinidng of a vessel wall, are seen iu their fully mature form. Blood clot is seen in interior of blood vessel. 44 THE CIROWTH OF ANTLERS SECTIONS FROM DOG'S EPIPHYSIS NEAR JUNCTION WITH DIAPHYSIS-FOR COMPARISON Fill 38. HEOTION 5011. — OBJECTIVE 4 mm. 4 eye-piece. Osteoblasts on diaphyseal side of epiphyseal cartilage arranged in rows Slirroundin.'; themselves \vitli ossein — seen on right hand of figure. *■- ■ Fill. .30. KKCriON ."1I3.--N0, .'! — I mm. objective. 2 eyepiece. Osteoblasts assuming mature form in transition of cartilage into bone. Ossein lic^iiiiiing to be deposited. Cartilage capsules have mostly disappeared, traces 01 longitudinal lines still remaining. SP]CTION FP.OM DOGS EPIPHYSIS 45 Fi.i. 40. SECTION 505. — (4)— 4 mm. objective. 2 eye-piece. Osteoblasts beginning to assnnie n\ahire form in cartilage at epipliyseal line, the cartilage envelor^.s iiaving almost ilisappearoil. Fl<;. 41. SECTION 513. — No. G — 4 mm. objective. 4 eye-piece. Transition from cartilage into bnne, mature osteal >la>;ts bein^ surrounded with ossein and incorporating themselves into bone. Osseous tralwculae in process of formation. 46 THE GROWTH OF ANTLERS Fi.;. 4-2. SECTION 507. — 4 mm. objective. 2 eye-piece. .Alatiire osteoblasts are seen inside and outside spaces and are being surrounded by ossein in formation of bone from cartilage. '<*^ \ SKC'TION 512. — 4 mm. objective. 2 eye-piece. Osteoblasts of mature form being enveloped in bone. Osseous trabocula in process of formation from cartilage, indications of enrtilagi-, capsules still remaining. OSTEOBLAST EMBEDDING ITSELF 47 The osteoblast embedding itself in ossein. When osseous trabecular are forming, rapidly multi- plying osteoblasts pavement the periphery and add to the circumference of the area by imbedding themselves in fresh osseous increments. Once they have surrounded themselves by osseiii, the osteoblasts become part of the fixed osseous structure and are regarded as bone cells, each of which controls, probably under the influence of the trophic nerves, the osseous area which immediately surrounds it. TJie Osteoblast may free itself from tJie surrounding ossein. When conditions a]-e normal, the cell may remain quiescent imbedded in its calcareous sun-oundings, but when stinuilated, it can promote the dispersal of its solid walls by causi]ig absorption of the lime salts which are removed through the blood stream ; the regenerating process is set up and the young cells assiune the role of osteoblast, being ready to take part in fresh osseous deposition when normal conditions are restored. Osteoblasts may evolve into bone in., eitlter of two ways : direct and indirect bone formation. From the germinal layer the osteoblasts may evolve into bone directly, or pass through an intermediary cartilaginous stage, from which they become finally converted into bone. These two ■ methods of direct and indirect transfer- ence of the osteoblast into bone may be seen in the same antler at the same time, though usually at some distance apart. The indirect method, where the osteoblast passes through a cartilaginous phase before it is converted into bone, is the predominating one in the development of the deer's antler. It is to be noted that the antler is 48 ,^ THE GROWTH OF ANTLERS primarily formed in a mass of cartilage springing fi'om the osseous fixed tissue cells of the pedicle and adjacent skull, and that any subsecjuent direct transference into bone, which may be seen in the same antler, is an evolu- tion from this base. Both direct and indirect modes of ossification may be seen in processes of repair after fracture and injuries in the lower animals and in man; the process of repair of the same bone, the tibial diaphysis for instance, mav assume either the direct or indirect method according to the conditions under which it is placed, though under ordinary circumstances, where considerable movement takes place between the fragments, the in- direct method — healing through cartilage — is the rule. ^^^Jere fixation of fragments of fractured bones i.5 brought about immediatelv after the injury, and the immobilization is maintained, healing takes place principally by the direct method. The osteoblast is the same cell which is evolved from the embryonic tissue, whether it passes directly into bone, or through a phase of transition cartilage. In either case it arrives at a definite shape and contour and becomes imbedded in a matrix surrounded by cal- careous salts — when it assumes the role of a bone cell. When the germinal layer is about to pass directly into bone, the osteoblast assumes its mature form, but when the intermediary cartilaginous t}'pe is assumed, the mature type of the osteoblast is delayed in appearing until toward the end of the process, when the bone formation is about to take the place of the transition cartilage. Direct hone formation. The photomicrographs of the sections illustrative of the method of direct bone formation occurring in the DIREf'T BOXE F0R:\[ATI0X 49 antler of the deer have been taken mostlv from some of the tines of antlers of the Fallow deer of about eight weeks' gro^^^;h. At this stage in the development of the antler some of the tines were in process of sprouting from the main stem. Avhile others had attained about one half of their gro^^'th, though they were still in process of evolution. Some of the sections were taken in series from near the tip oi the latter, while. l:)v wa}- of com- parison and contrast, a few were taken from near its base. Those sections from near the tip of the tine showed the bone formation to be direct. Those from the base of the tine, though more mature, had the appearance of indirect formation of bone through cartilage. Direct bone formation has not l>een found in the main stem (beam) of the deer's antler, its ossification being through cartilage springing from the pre-existing cartilage and l_>one of the pedicle. As one finds dii'ect bone for- mation occurring in some of the tines, toward their tip, it is probable that one might also find it in the terminal processes of the main .stem toward the completion of its evolution. Direct Iwne formation, as far as tlie present investigation goes, has cbieflv been found in the tines of the fallow deer. The antlers showed vigorous formation of bone through cartilage of the main stem and the Inisal portions of the tines, while tlie terminal parts of the same tines developed through direct bone formation. 1 One would. (/ priori, look for the direct method of bone formation, as likely to occiu' in the expanding palmate jDortions of the antlers of the reindeer and moose varieties, as the flatter formation of the palmate form would lend itself more readilv to that mode of 'Ltire^-t foniiatiuii has .-iiibsei[uently been fcmnd in tlie antler of the red deer niider similar conditions depending on tlie stage of its development. 50 THE GROWTH OF ANTLERS osseous development than the cylindrical mass of tlie main stem. Hitherto no opportunity of investigating the histological phenomena occurring in f/roiving antlers of the moose or reindeer has been had by the author. It is also possible that the relative amounts of bone produced by cUrect and indirect formation may vary according to circumstances, such as the condition of the animal. The sections have been made in series from without inwards, the first showing the superficial layers of the cutis and the substratum of eml>ryonic osteoblasti(- tissue, the latter ultimately develojjing into dense sclerosed bone. The cutis in tliis specimen is thinner than that covering the main stem of the antler. Any cuticiilar appendages which have dipped into the base- ment of the epithelial layer are extruded by the advancing osteoblastic encroachment. There seems to be little or no interchange of blood between the l)lood vessels of the underlying bone of the antler and those of the epidermal layer- -the velvet. Whether by differential coloured injections the vessels of the cutis and tliose of the interioi' of the antler could be shown to have some slight inosculation has yet to be determined, but there is certainly no obtrusive evidence of such inosculation in the antler at this period.^ If it does occur at any time, it would probably l)e found duj'ing the earlier periods of antler gro\vth, and not toward the completion of the process, when the osseous matter has absorbed all the pabulum, for its rapid production and then shut (»tt' the supply of blo(jd through the vessels by c(jmpressing them circumferentially and finally oblitci'ating them by the rapid encroachment of ^Siicli iiijectiiiiis liave Iji'uii tli(!(l Ijy tlic aiitlior uiflioiit slii.wi]ij^ inOHi-'ulatioii betwceu the ciiticiilar vessels ;uiil those (jf tlii! iiiteiiui-. DIRECT BOXE FOR^IATIOX 51 sclerosed Lone. The absence of sncli inoscnlation between the vessels of the interior of the antler and those of tlie veh'et. hastens the separation of the latter when the coronal abutment strangles the long A^essels of the cntis at their base. Had there Ijeen inoscnlation. the velvet would liaA'e remained longer and would proljablv have Ijled when separating from the bone, unless the vessels of the bone had previoiislv becijme oljliterateil. In tlie direct formation of bone one sees in the earlv perioil a syncitium almost identical with that seen in the indirect mode of lione formation (Fig. 49). In the same section almost contiguous with the field from which Fiff. 49 was taken, the di.stinctive cellular development ]jei-uliar to the embryonic form of direct < isseous formation is observed (Figs. 50 and .51 ). Within both the beginning of the deposit of ossein is seen, but nune di.stinctlv m the hitter. In Fig. 52 the osteoblast is beginning to assume its mature fr)rm and to deposit ossein in its periphery, so as to form a layer of bone in its eai-lv stage. In the succeeding views, tlie mature form of the osteoblast is more distinct and tlie osseous trabeculae better formed. The pa^•ementing of tlie tralieculae bv the o.steoblasts and the envelopment of the cells in the ossein so as to make firm Injue are all represented. Direct bone formation bears a resemblance to the ossification in the parietal liones of the skull. r)itra)iienibnuioi(S ossification. Here, as in the jjarietals. there is occasionally a .slight appearance of fibro-cartilage. In the human parietals one sees this at certain stages in the foetal developments and in regeneration taking place in the parietal bones after injurv, there is often seen a slight cellular zone some- what resemljling fibro-cartilage appearing in the midst of the predominant characteristics of direct bone formation. 52 THE GROWTH OF ANTLEKS DIRECT TRAXSITION OF OSTEOBLASTS INTO BONE v4 ^w^ »» ^f-t Fio. 44. SECTION 280.— FALLOW liKEli .\NTLEK, 2/3KLj GKOWTH, NKAK TI]' OK TINE. 4 mm. 4 eye-piece. Cutaneous tissue, hair bulb in ser-tion — dirertly cohering embryonic form of a?teoblastic tissue. V'^m ^j.^ J" Fi... 4.;. HECTIOX L'SO. — K.U.LOW DEEl! ANTLER, 2, OKD GKOWJTI, NEAT. TIT OE TINE. 4 mm. 4 eye-piece. Cutanei.'ij5 layer, hair bulb in section, in midst of embryonic form ol osteo- blastic tissue. DIRECT TR.JlXSITIOX \ X yi-:-: - if .■T ■■^- -.V « > • Ki(.. 41;. SKfTutN 2S1. F.\I.L<:)\\ liKKH ANTr.ETl, 2 ;-!l:[i i.P.ri\\T}J, NKAli TU' 1 iF TINh!. 4 i["im. 4 eye-j'iece. J-Iair folliiie, dippiii'_' intf.i eiiibrymir n-tt-oMa^tic tis-juf , Fi^.. 47. KKCTKiX :.'S1. — FALLOW J jFER AXTLKI:, 2.'iR1' GROWTH, NEAR TIL OF TINE 4 inrn. 4 e^e-piece. Embryonic loriii of ostfublastic tissue (uat I'ha^e). 54 THE GROWTH OF ANTLERS Fig. 48. section 281. — fallow hekr axtlkb. 2/3rn growth, near tip of tine. 4 mm. 4 eye-piece. Embryonic osteoblastic tissue, beginniag to assume distinctive cellular growth. Fig. 49. section 2s1. — fallow deer antler, 2/3rr) growth, near tip ok tine. 4 mm. 4 eye-piece. Embryonic osteoblastic tissue, osteoblasts being transforn\ed directly into bone. DIRECT TRANSITION ^ A^;* ?;*' SEcno.N 280. — FALLOW i>h;i-:k a.ntlkl, L';^!l;ll (JKowth, nk.m; iir df iin'f. 4 nun. 4 eye-piece. Embryonic osteoblastic tissue, osteoblasts transforming directly into bone, and beginning to pavement iirimiti\'e trabeciila. 3 m.:^;-ri x. .*;y%. Fig. .51. SECTION 281.— FALLOW DEEK .\XTLEK, 2/3kD fiRllWTH, NEAR TIP OF TIN'K. 4 mm. 4 eye-piece. Evolution of osteoblasts directly into bene. Osteoblasts beginning to approach mature form. 56 THE GROWTH OF ANTLERS « i* m. '■^ ,,,' i ■-■■' ■ « ■ '.■»'>*'•.- - . • 1 'j>. ' i?;.:- ¥. w % ' ' w - ^^ .:. J - ^ Fig. 52. kkction 330. — roe deer antler, sprouting antler, vf from tip of tink. 4 mm. 4 eye-piece. Imperfect cartilaginous fonn;ition (fibrivcartilaginous), between direct and indirect bone formation. Osteoblasts assiimiiic; mature form inside of spaces — cart, cells. Sl'K'TION 450.~FALL(l\V ItEER ANTLER, SPROUTING 1 V' FROM 'I'll' OF TINE. 4 mm. 2 eye-piece. Osteoblasts passing directly into bone^bone trabeculae furmiug, (Uem- braTioiis bone.) DIRECT TRAXSITIOX ^ ? SKfTIOX 450,— FALLfiW Df:P;K ANTLEH, SPHOI/TIN*. U" i-l;OM Til OK TIXK. 4 mm. 2 eye-i>iece. Osteobla-ts ]r.:--in^^ directly iiitn >,'IJ AXTI.KIl, 1" FIIOM TIP OFTIXE. 4 mm. 2 e^'e-piuce. Osteobl-ists at i-iid of triibccula iiicorpor-atiiii.' themselves into bone. Fif!. .17. SUCTION 450. — E.M/IOW IJEKR STRorTINO .\NTLEH, IV' KKOJI TIT OF TINE. 4 mm. 2 eye-piece. Dense bone \\-itIi osteoblasts on tnitsiile ami incorporated into the bone as bone cells. EVOLUTION OF BOXE THROUGH OARTILAOE 59 The evolution e>f bone through raiiihige {Indrreet hone formation). Specimens from the Eed Deer (cervus elaplius). the FaUow Deer (cervus dama) and the Eoe Deer (capriohis) have been examined. Indirect bone formation — tlie evolution of bone throu^rh cartilage — is the predominant method seen in the development of the Deer's antler. The whole basal .stmctiire springs from pre-existing bone in the pedicle and passes through the cartiLiginous phases before evolving bone in its final stages. The same appearances are seen in the earlv eml.irvonic tissue, from which the indirect bone is evolved, as were seen in tlie embryonic tissue from wliidi the direct boi\e was formed. So that, at an earlv period the embrvonic tissue from which thev both severally spring is histo- logically relatively indrstinguishable ' (Figs. 58. 59. 60). Both forms spring from an antler whicli ]:irimarilv is formed in cartilage. The sections which follow have an ever increasing di.stinctive cartilaginous appearance (Figs. (U. 62et seq.). The better developed bone, as seen in Figs. 69. 70. 71, 72. shows the appearance of an Haversian svstem with its concentric rings. The spaces are still filled vitli osteoblasts embedding thenrselves m the peripherv and advancing the bone formation centripetallv. and so lessemng the lumen of the space and finally probaljlv effecting its clo.suxe as the bone ad^-ances towards its dense sclerosed end. In the succeeding views, the matuie form of the osteoblast is more distinct and the osseous traljcculae ' E\"eii in iimre mature f'Hiiis of Ijniie funjiatiLHi such as in e]jipliv>.Hal plates rif oaitilaye tlieie may be seen ruiitigiicnis cartilaginous cells ni ideiitiral form, the one dotined for epiijliVNeaJ. tlie other for diapln .~eal iCrowth. 60 THE GROWTH OF ANTLERS better formed. The pavementiiig of the trabeculae by the osteobhists and the envelopment of the cells in the ossein so as to make firm bone are all represented. When the osteoblast assumes the form of transition cartilage it weaves a capsule round itself, in which it lies imbedded as long as the cartilage exists. When the promptings of higher development stimulate the osteoblast, it assumes its mature form, which is followed inunediately by a series of chaiiges in the cartilage capsule. EVOLTTTION OF BONE THROUGH CARTILAGE (IXDIRECT BONE FORMATION) ''4^-4 A 'it-/- ■'i'M' 'cUv •^^ km ■' Fig. 5S. SK(!TION IS.— FALLOW DKEH ANTLER, 3/4TH GROWTH, 8" FROJI TIP. 4 mm. 2 e3-e-piece. Osteoblastic embryonic tissue Irom which cartilage ami bone is Hltimatel.v evolved. The same phase is seen in direct transition. EVOLUTION OF BONE THROUGH CARTILAGE 01 •^MfiS^^m^ Fiu. 59. SKCTION :i51.— RKIi DEER SPROUTING AXTI.ER, NEAR 'I'll'. 4 mm. 2 eye-piece. Osteoblastic embryonic tissue, o ph.asc in evolution of cartil.iL"' and bone. Fjg. bo. section o.ol. — red deer sprouting antler, near tip. 4 mm. No eye-piece. Osteoblastic embryonic tissue assumin'j cellular formation marked on cine side of field. 62 THE GROWTH OF ANTLERS .^^01^ Fig. 61. section 351. — red deeit sprouting antler, near tip. 4 mm. 2 eye-jjiece. Cellular formation more pronounced. Blood vessels beginning to penetrate: Fig. (J2. SECTION 351. — RED DEEU SPROUTING ANTLER, NEAR TIP. 4 mm. 2 eye-piece. Cartilage cells taking on more distinctive appearance. Capsules beginning to eiiow. EVOLUTIOX OF BOXP] THROUGH CARTILAGE 63 NKCTION 4:ia.- KM Kic. (il!. -KM. IJIW IjI:KH SI'KdlTINi. AN'TI.KK, .\EA1{ il P. 4 mm. 4 eye-[)iecf. ( ';lttil;i<:r ;i--ll[Ililll.' ilc-rillitt.' fi.ritl. SKI-riON :-!4l>. — REP D 4 II Jilood vessfli Ijegiimin Fic. 64. n DEKI; SI'HOUTIN'G ANTI.EE, NE.M! Til'. 4 mm. 'J eye-piece, ■iiiing to penetrate the immature cartilage. Fir.. 64. ■ION :-!4i;. — REP 64 THE GROWTH OF ANTLERS Fii:. 1)5 SECTION 423. — FALLOW UKER SPROUTING ANTLER, 1" FROM TIP. 4 mm. 4 eye-piece. Cartilage well fonned, capsules distinct. SECTIO.V 454. — FALLOW DEER SPROUTINC ANTLEH, J" FROM TIP. 4 mm. 4 eye-piece. Cartilage fully developed, tliin-walled blood vessels penetrating and ossein beins deposited in periphery ol cartilage cells. Osteoblasts beginning to assume mature form inside cartilage envelopes. EVOLUTION OF BONE THROUGH CARTILAGE 65 Fig. 07. skctiox 335.— fal[,ow deer antler, 2|'^rr) growth, s" from tip. 4 mm. 8 eye-piece. Fully formed cartilai^e with multiple osteoblasts within capsules. Some osteoblasts also on outsiile, free. Cartilage capsules are thinning:. Flu. tiS. SECTION' I:!.")!. — HEI) MEEK SPROUTING ANTLKK, >'EAI! TIP. 12 mm. No eve-piece. C.irtil.ige en rruisse. E 66 THE GROWTH OF ANTLERS EVOLUTION OP BONE THROUGH CARTILAGE (INDIRECT BONE FORMATION) Fig. 0:1. section olt. — fallow hkki'. an'tlkk— eight weeks' growth, near base. 4 mm. 4 eye-piece. Osteoblasts embedded in ossein. Appearance of Haversian system — osteo- blasts still lining spaces. Fig. 7(1. section ;->17.— ealliiw dekr antler— eight weeks" growth, near liase, 4 nnn. 4 ej'c-piece. Haversian sy.stem beginning to be fonned — osteoblasts still lining interior o£ boue spaces and congregating therein, threatening occlusion. INDIRECT BOXE FORMATION 67 • ^■l■"">^^. SECTION 280. — FALLOW DEER ANTLER, 2/3RD GROWTH, NEAR BASE. 4 mm. 4 eye-piece. Appearance nf Haversian systems beginning to be formed— osteoblasts still lining interior of bone can:ils. This may have formed in cartilage at Itase of tine of antler. Fig. 7 SECTION 2S0.— FALLOW LIEEE ASTLEE, 2/3k1) GEOWTII, XEAE EASE. 4 mm. 4 eje-piece. Early indications of Haversian systems, but as this section was from base oi: tine it may have been formed originally in cart,ilage. 68 THE (iROWTH OF ANTLERS Chanf/es in the cartilage capsules during evolution of osteoblasts into bone. After the cartilage capsules have served their puipose they may undergo one of several changes : first, the disintegration of capsules and freeing of osteoblast ; second, the flattening of capsules and matrix forming from them. (1) Disintegration of cartilage capsule and. freeing of osteoblast. The capsules may become attenuated and ragged, and the osteoblasts (the " cartilage corpuscles ") being freed congregate together in spaces or pockets in the midst of the cartilage. Active osteoblastic proliferation ensues both inside the disappearing capsule and especiallv in the spaces where the free osteoblasts congregate. In the periphery of the osteoblasts congregated in these spaces, ossein is deposited, enclosing the osteo- blasts as bone cells ; trabeculae are soon formed and rapidly assume the characters of growing bone. These trabeculae are always being augmented in size by peri- pheral increments aided by the pavementing osteo- blasts. Spaces in the interior of the trabeculae are likewse paveraented with osteoblasts which fill the space centTipetally. Ossein also coloims the cytoplasm of the osteoblast. Figs. 73 to 80. Such changes are generally seen in the neighboiuiiood of thin-walled blood vessels which have penetrated the cartilage. EVOLUTION OF BONE THROUGH CARTILAGE (INDIRECT BONE FORMATION) i 9 ■r Fir.. 1-A. SKC'J'ION 4(15. -FALLOW MKLlt ANTLER, 2/oKI' GROWTH, 2" l-IIoM Til'. 4 mill. 4 e_ve-piece. Cartilage capi^ulos (lisapi'i'ariii^ setting ostcublasts free. Osseiu bogiiiiiiiig to bo deposited in iiuitrix. ^^^ :M Fig. 74. section ;>(id.— keh i>eee .sprouting a>tlep, 5" from tit. 4 mm. 2 eye-piece. Disappearing cartilage capsules, multiple cells inside capsule. Seven osteo- blasts in one capsule. Osteoblasts assuming mature form inside cartilage envelope. 70 THE GROWTH OF ANTJ.ERS * ^ Fl<:. ir,. SECTION 335. —FALLOW DEEK AKTLEE, 2/3HD GROWTH, 8" FEOJI TIP. 4 mm. 8 eye-i)iece. Cartilaee capsules disappeariiifj, osteoblasts becoming free. SKCTIO.M :'.35.— FALLOW IIEKR ANTLEE, 2/3k11 GROWTH, 8" FROM TIP. 4 mm. 8 eye-piece. Osteoblasts frecii)? tlieniselves from cartilage capsules and beginning to assume mature form. DISINTEGRATION OF CARTILAGE CAPSULES SECTION 335. -FALLOW DEER AKTLKR, 2/3RD GItOWTH, S" FROM T]r. 4 inui. 8 eye-i)iece. Cartilage capsules disappearing, osteoblasts being set Iree, and beginning to assume mature form. Osteoblasts escaping in groups. » • Fig. 78, SECTION' .335. -FALLOW DEEl! ANTLER, 2/3RD GROWTH, ,S" FROM TIF. 4 mm, .S eye-piece. Cartilage capsules disappearing. Osteoblasts being set free. 72 THE GRW^^TH OF ANTLER.S SECTION :^3(i.— FALLOW DEEK ANTLEH, 2/Hr1) GItOWTH, ><" l-'UOll TIT. 4 iiiiii. 8 eye-piece. Cartilaee capsules disappcariJig, osteoblasts beginning to assume luatiiie form inside capsules. fk "^-^^ •4 \^^'^ ^■ ^ i^^a;. SO. ("'TrON ;!Mr».-- FALLOW nEKR ANTLER, 2/8rd GEOWTH, S" KBOM ' 4 mm. 8 eye-piece. OsteolilaKts !)einL; set free from ilisint.ogratin<^ cartilaginous nmti'ix. C^ARTILAGE CAPSULE BECO-MES FLATTENED 73 (2) The cartiku/e capsule becomes tliicker andflatteited (tad 'participates in the formation of matrix. (2) The cartilage capsule, instead of attenuating, becomes thicker by encroacliments inward toward the contained osteoblast (or corpuscle), which meanwhile becomes smaller and approaches its mature t}^ie. Then there appears to be an increasing distaiice between the corpuscles giving an increased niatrix. The capsular substajice has fused i}ito a matrix. Fios. 81 to 85. EVOLUTION OF BONE THROUGH CARTILAGE (INDIRECT BONE FORMATION) Fig. 81. SKCTION 475.— F.\LLOW IlKEli A.NTLER, 2;'3bL1 GHOWTH, 2" FROM TIP. 4 mm. 4 eye-piece. Cartilage eapsules broadening into matri.x. Ossein beginning to be deposited. 74 THE GROWTH OF ANTLERS ?*^^ *%^ Fig. 82. KHX'TKJN 47.^.— FALLOW DEKH ANTLEB, 2/3kD GROWTH, 2" FIliJM TIP. 4 mm. 4 eye-piece. Cartilage capsules broadening into matri.\, shaded with ossein. Osteohlasts assuming mature tonn inside ol capsules and outside in pockets. Thin-walled blood vessels in periphery. yt ' W »;''S;.^ .^ v: V. 'i'>^ • Fig. s:i. SECTION 477- — FALLOW DEKH AN'I'LKU, 2/ol!|] (iROWTH, 2" FKOM TIP. 4 mm. 4 eye-piece. Cartilage capsules becoming flattened into matrix and shaded with ossein deposit. Osteoblasts assuming mature form inside of capsules. CARTILAGE CAPSULES BECO.MIXG FJ.ATTEKED 75 \« t"i' '^«/^i:r-;^4)j/ Fl.:. S4. SKUTlns 4G.J. — FAi.lJiW ]1EE)I A.NTLEH, 2/3UI) GROWTH, 2" FROM lir. 4 mm. oljject glass. 4 eye-ijiece. Broaileiiing of cartilage capsule^ into matrix in wiiieh o^^^ein i^ l^oiniz ileposirpil. i* »,■/ ,-« .^■^ Fig. S.T. SKCTIO.N' 47-5.— F.M,LOW DKKH .i.XTLER, 2,.'iRD GROWN', 2' FROM Til'. 4 mm. object glass. 4 eye-piece. Cartilage capsules broadening into matri.x, in whicli ossein Is deposited. Free osteoltlasts ionning in pockets. 76 THE GROWTH OF ANTLERS Defosits of ossein round osteoblasts and in matrix. Coincideiitally witli this increase of matrix Ijetween the corpuscles, the reniaiiii]ig capsules and the matrix formed from them l)ecomes filled with deposits of ossein, sometimes appearing as a fine haze or shade over the flattened framework ; at othei's the deposit is particulate and often spherical in shape, the spheres being veiy variable in size as if the}" had been sprayed on. This deposit of ossein is sometimes seen in the capsular framework early, before it has become flattened out, at other times it is only after the fiatteuing that this granular deposition of ossein appears. In either case, as the matrix increases, the deposition of ossein in- creases. The osteoblast assumes the role of bone cell. The osteoblast (the Cartilar/e corpi(.scle) which, during these changes, has assumed its mature form, remains in situ, becoming imbedded in the tissues which it gradually forms round it into bone, the osteoblast then assumino- the role of bone cell. Osteoblasts 'pave)iient tlie trabeeulae. 1'liese two methods of the evolution of cartilage into bone may lie seen not only in the same specimen but sometimes in the same field. In all these cases it is the osteoblast which is the energizing agent, the capsule playing a mere passive part. Whatever form is first assumed, free osteoblasts from the same source line the trabeeulae and may lie seen incorporating themselves into bone, generally aug)ue]iti]ig that already formed. OSSIFICATION ADYAXCIXG IX CARTILAGE 77 Ossification a/Iiyincitu/ ijotli centripetaUy and centrifagaUi^ in cartilarje. Bone formation is ftequently seen commencing in the periphery of cartilaginous masses and suiTouncling these and ejiclosing well foTinecl cartilage toward the centre. In such cases bone formation advances centripetaUy, until the whole island becomes converted into bone. The osteoblasts in this case remain iirside their cap- sules which gradually form into a matiix enclosing the osteoblasts as bone cells. AVhile ossification proceeds centripetallv, enclosing the cartilaginous mass, and converting it into bone, there is at the same time ceiitrifugal augmentation fi'orn the periphery of the bone first formed, osteoblasts pave- menting its circumference, each adding its quota to the increase. Blood vessels ui. relation to osteoblastic hone fomtation. Part played hy blood nt tlie erolafion cjf hone "While the osteoblast in the early stage develops quite independently of blood vessels in its immediate vicinity. and appears i)i a form of tissue in which few blood vessels exist, yet the osteoblast seldom as.sumes its matur'e form until thin-walled blood vessels peiietrate into its vicinity, after which the osteoblasts become very active, proliferation ensues and ossehi is deposited in the tissue. The blood brings pabulum for the increased mitritioii of the o.steoblast and ossein is conveyed to the tissue at the same time. The osteo- blast exerts a selective influence over pabulum carried bv the blood, extracting the ossein from the blood and fixin<2: it in the matrix round itself. Figs. 8(3 to 89. THE GROWTH OF ANTLERS EVOLUTION OF BONE THEOUOH CARTILAGE (INDIRECT BONE FORMATION) VASCULARISATION OF CARTILAGE ^\ .A' l • ^ .* *» Fig. NS. 8kcti0n 454. — fallow deer kl'kouting antlkh, 4" from til', 4 mm. 4 eye-piece. Osteoblasts and cartilage capsules becoming impreguated with ossein in neighbouriiood of thin-wnlled vessel. 3^>: I^IG. 8!:l. SECTION 45:1 — FALLOW DEER SPROUTING AXTLKK, ^'" FKOM TIF. 4 mm. 4 eye-piece. Bone t'oniiation encroacliiiig od lumeu of a blood vessel wbicli has penetrated the cartilage. Obliteration of blood spaces thus occurs by the deposition ot cartilage centripetally. 80 THE GROWTH OF ANTLERS The vascularization of the antler. The deer's antler in its sprouting stage is full of blood, thin-walled blood vessels appearing everywhere round which osteoblasts grow and which penetrate into the embryonic layers and cartilage. There is at the highest point of the stem of the antler an ever advancing rapidly proliferating zone of cartilage which is followed by blood vessels which penetrate the advanced tissues. Obliteration of vessels in antler by centrijietal osseous de-posit. Solidification. The blood vessels appear in great abundaiice whenever the osseous growth is rapid, and in the antler the thin- walled blood vessels are very large ; often only a single layer of endothelium separates tlie blood current from the neighbouring structures. After the bone is well formed, it is interesting to note that the calibre of these vessels becomes less and less, by osseous encroachments upon their periphery, spreading centripetally, which diminishes their lumen and finally obliterates manv of them (Fig. 89). The tissue which at an early period was soft and full of blood becomes solid and avascular. The more perfectly the vessels perform their function the more speedily is their own oblitera- tion secured. A similar deposition of thin-walled vessels prior to bone development is seen in experiment Avhen dog's bone is grown in glass tubes and also in growth and repair of human bone generally, though in the later the calibre of the vessels do not assume the same dimensions. OSTEOBLASTS DO XOT GROW FRO^t BLOOD VESSELS 81 The osteoblasts do not grow from the blood vessels. The osteoblasts are not seen in the blood A^essels normally and do not grow from them, though it is possible were they introduced they might be carried l^y the blood stream. The osteoblasts may be seen Iving on the surface of the bone on the outside of the Ijlood vessels iii the same way as they may l^e observed pavementing the growing hone where blood vessels are not immediately adjacent. In histological examination, osteoblasts in certain specimens may be seen adherent to the outside of blood vessels where, owing to the action of reagents used in preparation the A'^essel has shra)ik from the osseous trabeculae, drawiiig the osteoblasts with it (Fig. H7). CHAPTER III THE SKPARATIOX OF THE ANTLER The blood supplies of the antler and the effect of their arrest. The process of separation of the antler. Preparation for shedding appears at the birth of the new antler and increases during its vigorous growth. Process commences at level of corona. Obliteration of superficial vessels at corona. Corona presses through cutis and superficial vascular supply is cut olf. Osseous tissue in antler becomes avascular and dies — the changes in the vessels. The separation of the dead antler by means of intensified action of the living tissue in pedicle. The production of granulation tissue in pechcle. The shedding of the antler is an aseptic process occurring in the open air. The separation of the antler is dependent priniaiily on the withdrawal of its l^lood supply. In this relation it must l^e borne in mind that the vascular supply of the antler is from two sources, the main one beijig internal, giving pa.bulum to the proliferating osteoblasts and conveying the salts which the osteoblasts deposit as ossein ; the other is superficial, the vessels supplying the cuticular covering (the velvet), few if any capillaries from these vessels penetrating deeper than the cutis ; but the cuticular vessels aid materially in the mainten- ance of the temperature of the soft growing antler, while the active osteoblastic proliferation proceeds within. These two sources of blood supply require to be cut off before the ajitler and its velvet dies. The arrest of blood flow from the superficial vessels causes the drying up and shrivelli)ig of the velvet, but does not cause necrosis of the ajitler, which at this stage still continues to be S'2 THE SEPARATION OF THE ANTLER 83 supplied with blood from the interioi- of the pedicle, and the osteoblasts are still proliferating and depositing ossein tliough both are now somewhat toned compared with the exuberant previous growth. The centripital deposition of the osteoblasts round the blood vessels redirces their lumen and finally ol:)literates them. The blood supply to the interior of the antler must likewise be arrested before the antler dies or becomes necrosed. Ample provision has been made to effect both these purposes at the proper time. The process of separation, of the atUler. At the birth of the new antler, pi-ovisioji for its ulti- mate separation is already foreshadowed and prepara- tioii for its shedding may be seen during tlie period of its most vigorous growth. At the very outset, the pejit- up ossific pabulum emanating fi'om the pedicle of the sprouting antler overflows and foi'ins a circnmfeiential pj'ojectioji, afterwai'ds known as the corona., at about the level of which the ]>rincipal changes leading to ultimate shedding of the antler occurs. ^ Ossification in the growing antlej- commences in line with the corona, proceeding from the centre outwards, and as it becomes completed, the vascularity at that part visibly lessens, in co]itrast to the vascularity of the adjacent base of the antler on the distal side and of the pedicle on the othei'. The ohliteratio)} of the superficial vessels in thie cutis- veh'ct — at tlie corona. While these cluinges occur in the interior of the shaft, important ones ai'e simultaneously taking place in the periphery of the base, in the corona itself. At the ^ JMuch in the same way as osteoblastic granulation tissue sometimes overtlows the circumference of the femur after section of the shaft of that bone for amjjutatlou — forming a mushroom-shaped covering. 84 THE GROWTH OF ANTLERS outset the corona projects beyond the circumference of the pedicle, continues to increase circumferentially and Fig. S9a. RED DEER (CERVUS ELAPHUS)— SECTION OF ANTLER ABOUT TO SHED Adthok's Collection. A stage toward the shedding of autler. Section tlirougli sliull, pedicle, and base of antler. Antler is now dead bone with coagulated disintegrating nlood in it. The skall and pedicle are very vascular in preparation for shedding and regeneration of new hone. The portion of the antler abutting on the pedicle consists of dense white bone, presenting a convexity toward tlie pedicle. to send osseous projections between the subcuticular At first these coronal osseous irregu- blood vessels. OBLITERATION OF THE SUPERFICIAL VESSELS 85 larities form a protection for the blood vessels, as they lie embedded in the grooves, but gradually by the advanc- ing ossific invasion these vessels are not only embraced but their lumen is encroached on by osseous increments until they have been finally compressed and strangled. The edge of the corona ■pressing through the cutis of the antler. At the same time the edge of the corona still growing outwards, puts the cutis over it, and its contained vessels. upon the stretch, which consec[uently becomes thinner and ultimately gives way in front of the pressure, exposing the underlying bojie. Thus the superficial vascular supply to the antler — the long vessels extending from the pedicle to the tij) - is cut ofE, and there being no inosculation with the vessels of the interior, the whole cutis becomes avascular, dries, shrivels and peels off in shreds. This is known as the shedding of the velvet. The growth of the interior of the antler is however still active — bone being laid doAvn making for consolidation — though sclerotic changes have already supervened. The manner in which the velvet paits in front of the pressure of the corona somewha-t resembles the yielding and sloughing of the human cutis, in front of the anterior superior spines of the ilium, for instance, i}i cases of emaciation — without external pressure ; but in the latter case there is no increase of osseous growth, only the shrinkage of the cutis over the bony prominence, due to the want of nutrition, and the stretching of the skin over the underlying bony prominence. The separation of the mitler from the j^edicle. The osseous tissue within the antler at the level of the corona becomes veiy^ dense and gradually avascular 86 THE GROWTH OF ANTLERS — tlie lumen of the internal vessels being encroaclaed on by the rapid prohferation of the osseous tissue round them until obliteration of the vessel ensues. Thus an avas- cular barrier is formed on the side of the antler cutting off the blood supply, passing through the pedicle to the antler. The antler bereft of its pabulum ultinrately becomes dead tissue. The avascularity of the whole thickness of the base of the antler at the coronal junction is thus apparent, a dense white bone presenting (Fig. 89a). When this has taken place, the living bone requires to part with the dead antler and preparations are made on the side of the pedicle and adjacent skull toward this end. These are analogous to the shedding of dead tissue — necrosis or sloughs — which occur in other animal tissue as a result of injury or disease. Preparatory to the shedding great vascularity occujs in the pedicle and underlying skidl, the bone near the level of the dead antler becomes softened, ossein is absorbed and a granulation tissue, derived from the pre- existing osseous tissue cells of the pedicle, forms and gradually loosens the organic connections between the pedicle and the dead antler, which is finally floated off, fallijig by its own weight or by accidental contact with external objects. While those changes are occurriug, the free bone cells within the skull and pedicle proliferate with remai'kable rapidity and the proliferated cells, assuming the role of osteoblasts, are ready for fresh effort in producing a new antler. The proliferation of the pre-existing bone cells, in the highly vascularized adjacent skull and pedicle, form the granulation tissue which aids in the separation of the old antler and furnish material for the growth of new bone. SEPARATION OF ANTLER FRO:\I PEDICLE 87 Prior to those processes immediately concerned in the separation of the antler, the osseous tissue of the pedicle, and even the skull tissue from which it springs, present marked preparatory changes. Normally the bone cell is closely surrounded with ossein, but during these preparatory changes the ossein is absorbed from the immediate vicinity of the bone cell, which then shows itself distinctly isolated, as if it were in a cavity opened in the bone. Later, these spaces round the bone cells become larger and prolifer- ation of osteoblasts occurs within them. The Haver- sian canals become wider and osteoblasts congregate within them in ever increasing numbers. Blood vessels also increase in number and in size within the skull and pedicle, all denoting renewed potentiality for further osseous reproduction. It is interesting to note that the whole of the process of shedding of the antler takes place in the open air, and does so asejstically, and consequently mthout sup- puration. The animal cannot lick the part, as most animals do wounds in other parts of their body ; it has no hands to coiivey germs to the raw surface, and the part is too tender to permit the animal to rub the surface against external germ-laden bodies. The free growth of pre-formed granulation tissue forming over the raw surface at the pedicle prior to the shedding and the rapidit}' of the formation of the superficial layer — the stratum lucidum — of the cuticular covering contri- butes to this end. Doubtless suppuration may occur, as a possibility, in the pedicle at this period — a specimen of this kind having been sent me, sho^^^ng a partly necrotic pedicle fi'om a pyogenic osteitis and a consequent mal-formed aborted antler (Fig. 20). THE CiROWTH OF ANTLERS :*T, I ' WW u 1 f K]K. yo. 1. .SHED (DEAD) ANTLER SECTION' 281. — RED I>EE1! — ANTLER SHKll — SECTION' NEAR CORONA. A mm. No eye-X)iece. Dead bone — m.i bone cells — empty si^ices mostly. Kill. 91. . PREPARATION IN PEDICLE FOR SPROUTING ANTLER SECTJON lis?.— KEli IIEER SPROUTING ANTLEK, 2i" HIGH. Taken Irom near corona! line — showing old bone of pedicle from which fresh (Cartilage' is springing. PREPARATIOX IX PEDICLE FOR SPROUTIXCl AXTLER 89 Fig. ill'. 3. PREPARATIUX IX PEDICLE FOR SPR(_)rTIX(; AXTLER SECTION" ;-iSG.— EEI> DEEIl SPROUTING ANTLEK. 2}," 11H;H. 4 mm. 2 eje-piece. Bone in pedicle preparatory to issuing I'resii osteoblasts to form new antler. Osteoblasts accumulating in Haversian canals. ^ a- Fig. 9:!. 4. PREPARATIOX IX PEDICLE FOR .sPROUTIXi; AXTLER SECTION :Wi;. — EEll DEEI: SPROUTING .\NTLEK, 2A" HIGH 4 mm. 2 eye-piece. Bone in pedicle preparatory to sprouting — wide spaces seen round bone cells — first step toward regeneration. CHArTER IV XI'CLEAR lU'DDIXi; Xvielear Inuidiug ooourriug in osteoblasts in developing antlers. As seen oeeasionally inside of cartilage envelope. Much more frequently in free osteoblasts, ilany cells in all stages of groAvth seen near the cells exhibiting nuclear budding. Daughter cells Giant and multiple cells — their formation. Castration, its effect upon nuclear budding. Nuclear budding of same kind may be seen in epiphyses of dog and in human epiphyses and in pathological products. Notes on chromidiosis from Howard and Hertwig. Xuclcar buddiiu/. ^Miile examining sections of the deer's antler, nuelear budding was obsen-ed and was at tii'st regarded as an anomalous and accidental production, such as might arise possibly from antifracts. Inquiry showed, however, that miclear budding occurred so frec|uently and was seen in manv sections taken from the antlers of deer of different species, especially appearing at parts of the antlers wliere proliferation was most active, that it seemed to be other than a fortuitous production and rather that of cells preparing to participate in a general design. The data here are not coniplete. It presents a tield for further investigation . The folloA\'ing are the facts as far as obser^-ed : 90 NUCLEAR BUDDING 91 The phenomena of nuclear budding occurs in the osteoblasts in the deer's antler during its developmental stages. Occasionally it may be seen in a cartilage coi'puscle, while inside of its cartilage envelope (Fig. 103) ; much more frequently it arises from tlie osteoblast when freed from cartilage and when it has assumed its mature form and is actively proliferating before it is about to transform itself into boaie. In the latter, cells showing nuclear budding may be found in groups of twos and threes and as many as a dozen have been seen in a single field under a 4 mm. lens with 4 eye piece^ (Figs. 94 to 102). Nuclear liudding met with in the antler is coiifined to the osteoblasts and in them shows itself in cells which have reached or are approaching their mature form. The osteoblast at that stage is oval, with the nucleus (containing several spheres of iraclear material) situated peripherallv at the narrow end of the oval, and from that peripheral nucleus Inids are extruded, some of them at least carrving a halo of cytoplasm along wth them. In the vicinitv of cells exhibitijig juiclear liudding, numerous small cells are seen i)i all stages of growth, from that of the inunature, free nuclear buds, to small cells with their proportional nucleus and cytoplasm, aiid from these upwards to those of mature form and size. In one specimen (photographed) the nucleus and cytoplasm issuing froni the cell form a distinct bud-like and complete daughter cell issuing from the osteoblast. 'It is difficult to photograph these cells iu groups owing to the different levels in which the cells are situated, but with the alteration of the focus the ej-e perceives them direoth' through the lens or as transmitted to the screen. The fixing fluids used for the various antlers have been varied — strong spirit, formalin. Flemming's fluid, etc. It was endeavoured to avoid artefacts. 92 THE GROWTH OF ANTLERS From some cells two miclear buds extrude, though in the great majority there is only one seen extruding at the same time. A traihng thread of cytoplasm or nuclear substance is sometimes left attached between the nuclear bud and the cell. Nucleai- buds have occasionally been seen within the cytoplasiu apart from the nucleus. In one such instance, where the nuclear bud was found within the cytoplasm at a distance fi'om the nucleus, an indentation was left on the periphery of the cytoplasm, as if the bud had penetrated the cell from without. Search was made for evidence of a similar occurrence in other cells with nega- tive results, though there were many instances of nuclear bud-like bodies lying contiguous with or attached to the outer wall of the cytoplasm. In giant or multiple cells which are seoi frequently, the nudtiple nuclei may have been formed by nuclear budding into the cytoplasm. Though these multi- nucleated cells may also be produced by splitting off 7nultinuc]eated masses and by fusion, some compound cells appear to be undergoing division into single cells. Nuclear Inidding has been seen in the antlers of the Fallow Deer, Red Deer, and lees frec[uently in that of the Koebuck (the amount of bone produced in Roebuck is relatively small), occurring where growth of bone is quick'est and where osteoblasts were most al)undantly reproduced. NUCLEAR BUDDING f?^^ FKi. H + . 1. NUCLEAR BUDDIXt! MRfTKlN 11.— FALLOW IlEKK ANTLKH, 2/3llIl CIIOWX, S" FHoJI TIF. 4 mm. 8 eye-piece. Niif'le.'ir hiu] lieing sejiaratetl from niatiiri' lorni ot' (">.^te("tli!as.t. Fig. 9."i. 2. N'UCLEAB BUDDING .SECTION 11.— FALLOW DEEK ASTLEK, 2/3KI) IJROW.X, 8" FROM TIP. 4 mm. 8 eye-piece. Three maturely foniietl osteol'lasts sliowim: imelear buiMiiig. 9i THE GROWTH OF AXTLERS m' ^ ^. n'' ^.-l^-i^.# 3. NUCLEAR BUDDIXC- ^EfTIOX 12.— FALLOW DEER ANTLEK, 2, ;3KD GKOWN, S' FROM THE TIP. 4 inm. >< eye-piece. Mature form of osteoblasts in vicmity of l.ioue. showiiig nuclear biid.^ — som'.- iii act of separating. 4. ^► :rc • ... • ..^A ■* . * - ^, Fi.;. 117. 4. XITLEAR BUDDING hECTIOX IS.^IALLOVV J.KKfL AXTI.KK, 2 3hl' i.f'/'UN. M" t KMM Til'. 4 rnm. ."S eye-piece. Group of free mature osteohlai^t- near bone trabecula. exhibiting nuclear budding. XUCLEA7< BUDDIXG 95 Ki.;. IIS. .3. XUCLEAK r.UJDIX(.; SECTION ]:;. — FALLOW f)LK(; AN'ILKI;. 2 'A\:]} GROWN, S" KIlOM '11!'. 4 nil]]. S eye-iiit_-Cf. 3Jany osteoblasts iri thi.^ group, r-xhil:iitii]y unclear bu'l'liii',' — ^onie in iin.iC':'SS of separation. '¥' '*'^^<*. Fro. !MI. 6. XUCLEAR BUDDIXG SECTION I.":!. — FALLOW DKEK ANTLEK, L',, :'>Hr] GI;<".WN, 8" FKOM 'IIP. 4 mm. Groups of free mature osteoblasts— showing' nuclear buds, several exhibiting two buds. 96 THE GROWTH OF ANTLERS 4 ^ ® «» Fig. 100. 7. XUCLEAR BUDDING SECTION 11.— FALLOW JiEER ANTLER, 2/3RD GROWN, 8" FROM TIP. Mature form of osteoblast near centre of section, showing two distinct buds and one other projecting from side of nucleus. Inside the nucleus two more may be seen. ■m *Sk Si^iii *» WW Fig. 101. 8. NUCLEAR BUDDING SECTION ll.--|.-.\LLOW IIKEK ANTI.Kll, 2/:JHI) GROWN, 8" FROM TIP. 4 mm. 8 eye-X)iece. Appearance of danjzhter cell being thrown off fiom one of the group of two, where nuclear budding is taking place. XUC'LEAR BUDDING 97 ^9^ Fia. 102. 9. XUCLEAR BUDDING SECTION 12. — FALLOW ] )EEK ANTLEE, 2/3KI) GKOWN, S" FKOM TIP. 4 mm. 12 eye-piece. The sepftlatetl bud shows cytoplasm and darker portion Uke nuclfii^ at one end. Several bud-lilce masses are seen in the nucleus. # m -■'.V <:;*. 'St. c- r. ' Fig. lOo. 10. NUCLEAR BUDDING SECTION 12. — FALLOW DEER ANTLEE, 2/3rD GEOWN, 8" FROM TIP. 4 mm. 4 eye-piece. An osteoblast inside of new t>oue, showing bud from nucleus. G THE GROWTH OF AXTLERS Fig. 10+. 11. NUCLEAR BUDDIKG Photograph of a drawing by Dr. Jlacmurray of osteoblasts showing nuclear budding, the cells being taken from difierent fields and sections. GIANT CELLS, COMPOUND CELLS 1. (_;1AXT CELLS SECnON ;!35. — FALLOW DEER ANTLKK, 2/:'iUP GROWN', S" FROM Til'. 4 mm. 8 eye-piece. Early stages uf bone formation. Giant (raultipli') ci^ils seen tiiroiiyliuut tlie section. Many not in contact witli trabeculae. Fig. 10(3. 2. GIANT CELLS SECTION ;«.1. --FALLOW DEEK ANTLER, 2/3RD GBO\VN, S" FR05I TIP. 4 mm. S e3'e-piece. Giant cell (motlier cell ?) with long process ex'tending from its protoplas and containing many nuclei for separate cells). 100 THE GROWTH OF AXTLERS Fig. 107. 3. GIAXT CELLS SECTION 13.— FALLOW DEEE, 2/3KU GROWS, 8" FROM Til. 4 mrn. 8 eye-])iece. Smaller cells escaping' from compound cell {mother cell ?). Budding seen In one of the escaped cells. PROCESS OF REPAIR IN HUMAN TIBIA AFTER ACUTE OSTEOMYELITIS (FOR COMPARISON) <,.'■ .i^.-*J,' . %• Fig. 1U8. 4. GIANT CELLS SECTION JK.'-I. Compound cell — many such are seen in all the sections PROCESS OF REPAIR IX HL'^IAX TIBIA AFTER ACUTE OSTEOMYELITIS (FOR COMPARISOXi ^?Tj-.i»«,*|^^ .^..^ ,13*< -.-i.-. idTr ••i;* Fir;, lll'.l. 5. CTAX'T CELLS SECTION 4S3. Compound cells dividing into single cells. The rest of the tissue Is the embr\-onic form of osteoblastic tissue. like wliat is seen in deer's antlers. The check to the growth of the antler jjroduced by castration probably involves among other changes that of the cessation of nuclear buckling, and undoubtedlv restriction of regeneration of osteoldasts follows castra- tion. The author has had no opportunity of examining the head of a castrated animal — except as a presen-ed specimen m a museum and once in a living animal in captivity. Xow that nuclear budding has been recognized in the osteoblasts of the deer"s antlers, nuclear budding of a similar description has been foimd. much more limited in extent, in the rapidly gromng bone near the epiphvses of the voung dog. and it has been occasionallv seen in the transition of the human epiphyses into bone. In patho- logical processes, where tissue growth is rapid, nuclear 102 THE GROWTH OF ANTLKRS budding may also be found, sometimes in considerable quantity. The regenerative foree seen in tlie development of the antler is oTit of all proportion in excess of that exhibited in any other part of the animal's body, and this excessive reproduction of cells requires explanation. This is the more striking when the fact is recalled that the whole osseous pabulum originally springs from the narrow pedicle and neighbouring skull. The phenomena of nuclear budding as seen in many of these rapidly growing antlers seems to contribute to the reproduction of cells and nuxy be at least one of the contributory factors to the extraordinary rapidity of growth. In rapidly gromng malignant tumours, sucli as Sarco- mata, a somewhat similar form of luiclear budding is exhibited — which probably contributes to the rapid production of cells. 'I'hough instigated by micro- organisms the rapidity of gro^vth must in these tumom's be evolved by different biological phenomena from those obtaining in the normal tissue. In the antler the osteoblastic cells are an ordered, pur- poseful entity, playing their part in definite design, and ceasing when they have fulfilled the behests of hereditary law. In the quick groAving malignant tumours the constituent cells, stimulated by an extraneous alien force, proliferate Avith great rapidity, producing an inchoate mass, unlimited in extent, except by the destruction of the animal economy of their host. But in both, the vitality exhibited by these cells, their enormous pro- ligerousness and rapidity of production, is such that some other force than that seen in the ordinary methods of cell division, has to be evoked to account for their evolution. A somewhat similar phenomena to nuclear budding as seen CHROMIDIOSIS 1<»3 in the deer's antler — though differing from it. — is chroniidiosis, where the nuclear buds usually pass into the cytoplasm. Hertwig, in 1904, from observations on the actino-sphaerium, drew attention to the phenomena of chroniidiosis — " the throwing out from the nucleus into the cytoplasm — there to be broken down or extruded — of excessive chromatin staining nuclear material." .Since then he and his pupils — Howard, Popoff and others — have shown it to be a widely adopted method in various protozoa, in sex cells and in thymus cells, " of getting rid of excessive nuclear material and of restoring the nucleus plasma relation." ^ " In certain of the malignant and rapidly growing types of tumours, chromidiosis is seen and seems to play an effective role in the regeneration of cells, somewhat as is seen in protozoan, sex and thymus cells in production of mitotic division. It is evident that cells of such tumours must employ biological pro- cesses differing from those usually utilized in the normal tissue from which they spring. If the cells from which a tumour arisesxould only exhibit in their regeneration the same phenomena as char- acterized their normal matricial type, they would then run the same life cycle as these and would have the same destinv — there would be no tumour. " The relationship of amitosis to nuclear budding has long been recognized. In protozoan cells it is a true reproductive process. " Chromidiosis occurs previous to division in sex cells. The removal of the energy used up in growth may require phenomena other than the usual asexual division of the cells." Hertwig holds that conjugation is essentially a phenomena of cell regulation without which the cell must finally perish, and he says that so far as is known protozoa and sex cells are the only cells which have been able to preserve this most important regulatory process (" from the avoidance of and the recoverv from depression "). " Whatever its nature, the division energy ' W. T. Howard, On the role of Sudear Budding in the Regulation of Tumour Cells. Papers from the Lakeside Hospital, Cleveland, 1910. R. Hertwig, Uber jjiysiologische Degeneratiom bei Actinospkcerium. Eichhomi, 1904. 104 THE GROWTH OF ANTLERS controlling and determining nuclear budding seems to reside within the nucleus." " Nuclear buds tend to wander to the periphery of the cell. They may degenerate and become disintegrated or be extruded from the cytoplasm. They may divide by mitosis or amitosis — or they may separate with portions of the cytoplasm or mother cell, thus forming well regulated daughter cells capable of growth and of divisions bv either mitosis or amitosis."' THE EFFECT OF CASTRATION OX THE GROWTH OF THE ANTLERS The data regarding tlie efiect of castration on the growth of the antler has probably not been thoroughly wrought out, but sufficient evidence has been adduced to show that castration produces a profound efliect upon their growth, and though this may be expressed in a variety of ways, all of them indicate retardation or aixest of growth. This is especially marked in the main factor, the growth of bone of the antler. The effects vary according to the period at which the castration takes place, relatively to the growth of the antler. If the animal be castrated when the antler is fully groAvn, the shedding is retarded, and when it does shed, the base of the antler is seen to be concave instead of convex as it is normally.^ ' There are 1 1 specimens in the Royal College of vSurgeons Museum from fallow deer (Cerviis dama) which had been kept at Oultou Park, Cheshire, illustrative of castration in male deer. Some had one testicle removed. Some had one half of each testicle removed and some had both testicles taken away. In specimen 1557 — half of each testicle was removed and both antlers were shed but never afterwards attained full size ; bases of antlers were concave mstead of being convex as in normal specimens. Specimen 1567 — left testicle removed and left antler shows a correspond- ing arrest of growth. Sjjecimen 1569 — castration, antlers not shed at proper time and mal- formation by exostosis. EFFECT OF CASTRATION 105 The new antler, springiHg after castration, is dwarfed and malformed and the shedding of the velvet is retarded — sometimes it does not shed. According to Flower the horns are imperfectly formed and spongy, there being no true bone in their composition.^ ' "When castration i.s performed in an adult stag, it often dies ; liut when the animal survives during horn-growing time and the velvet is peeled oft, the horns are seen to be imperfectly formed and spongy, there being no true bone in their composition. Tliey do not solidify and are consequently of small benefit. The horns are never cast and the animal rarely lives to any age." — Sir Wilham Flower. INDEX. A. PAOB Alces Maohlis (Elk) Moose — head of • - ■ - - - 5 Analogy of growth of antlers to conical stump after amputation in child's femur or humerus ....--- 8 Analogy, of growth in Antlers, to diaphyseal cartilaginous plate - 10 Antler springs from one small centre of ossification in frontal bone 2 Antler, fracture of - - - - - - - - ■ - 26 Antler — pathological — osteomyelitis — stunted growth - - - 25 Antlers sprouting — in section — Red Deer, Cervus Elaphus - - 9 Antlers, Fallow Deer — eight weeks after shedding — section of pedicle, antler and skull - - - - - - - - - 14 Antlers, Fallow Deer, sprouting Antlers — five weeks after shedding 13 Antlers, Fallow Deer, sprouting Antlers — four weeks after shedding 12 Antlers, Red Deer, about to shed — section of skull and pedicle - 10, 17 Antlers cervus (red deer) -------- 30 Antlers, deformed result of fixing to pedicle ----- 24 Antlers growing, two weeks after shedding - - - - - 28 Appearance of pedicle and new antler two weeks after shedding - 9, 11- Appearance of Haversian system .---.-. g6-67 Arrest of blood supply of antler — its effect ----- 82 B. Blood vessels of velvet — their growth and obliteration - - - 11 Blood vessels beginning to penetrate immature cartilage - - (32, 63 Blood vessels in relation to osteoblastic bone formation - - • 77 Bone formation encroaching on lumen of a blood vessel which has penetrated cartilage - - - - - - - - 79 C. Cap of rejuvenating cartilage -------- 8 Cartilage capsules, freeing of osteoblasts ----- 68 Cartilage capsules becoming flattened • - - - - - 72 Cartilage en masse ---------- 65 Cartilaginous form of ossification - - - - - - 59 ci seq. Castration, its effect on nuclear budding - - - - - 104 Castration, its effect on growth of antlers . . . . . io4 Cervus Canadensis, head of - - - - - - - - 4 IN])EX -fallow cleer- -fallow deer- antlers- — sprouting —sprouting antlers- pedicle, portion of base of pedicle and four weeks after ■five weeks after Cervus dan:i8 shedding Cervus dama shedding Cer\'us dama — fallow deer- skull in section Cervus Elaphus — red deer — sprouting antler - - . - Changes in cartilage during evolution of osteoblasts into bone - Chromidiosis ------.--. Corona pressing through cutis of antler . - - . - Cromie antlers — views as to causation - - . . - Cutaneous glands in velvet ---..-. Cutaneous structures — velvet — covering antler 15, 16, 17, ]!l Cutis covering antler --.----. 107 PAGE 12 13 U 9 OS 103 85 7, 3i( 21 1, 22 10 1 5S D. Daughter cells ......... Deer's antlers a deciduous structure . . . _ . Dense bone forming (direct ossification) - ... - Deposits of ossein round osteoblasts and in matrix - - - 713 Direct and indirect bone formation ------ 47 Direct bone formation ----.-..- 4S Disintegration of cartilage capsules - - - - - (jS el ^eq. Dog's l^one epiphysis in section for comparison . . . . 4-1.^ 41; E. Effect of castration on growth of antlers . - . -104 Effect of injvu-y or disease of pedicle on growth of antlers - - 23 Emljryonic osteoblastic tissue ....... 54^ 55 Evolution of bone through cartilage — indnect bone forn:iation . 50 Evolution of the osteoblast -------- 33 Formation of dense bone Fracture of antler (I'ed deer) F G. 58 20 Giant cells 100 Glands cutaneous — in velvet ----- - 21 Green-stick fracture of antler ------- 26 Growth of antler affected by pathological conditions - - - 25 Growth of hair and dermal structures — on velvet of antler - - 17, 18 H. Hair bulbs in section — in velvet ------- 20-21 Haversian system, appearance of, in cartilageous ossification - - 60, 67 Head and antlers of Moose (Elk) — Alces Machlis . . - . 5 Head and antlers of Wapiti (Cervus Canadensis) - - . . 4 Histological development of velvet - - - - ■ ■ 15 108 INDEX I. PAGE Indirect transition into Ijone through cartilage - - - - 59 Injury or disease — effect of, on pedicle and growth of antlers ■ - 23 Intramembranous ossification .-..--- 51 M. Macroscopic appearances of specimens of antlers commencing to grow 28 Mature form of osteoblasts — in antler of deer ----- 35, 43 Mature form of osteoblast seen in dog's bone - - - - 44, 45, 46 N. Nerves of antler - - - - - - - - - - 18 New osseous growth springs from whole surface of pedicle - - 6 New osseous pabulum iDecomes cartilaginous and ossifies - - 8 Nuclear budding occurring in osteoblasts in antlers - - - - 90 Nuclear budding seen mostly in free-osteoblasts - - - 90 e« seq. Nuclear budding may be seen in epiphyses of dog, in human epiphyses very occasionally, and in pathological processes - - - 92, 102 O Obliteration of superficial vessels in the cutis ----- 84 Obliteration of vessels in antler by centripetal osseous deposit - 80 Ossein being deposited ------ 4U, 41, 66, 67 Ossification advancing both centripetaUy and centrifugally - - 77 Osteoblast, typical form of ------- - 35, 43 Osteoblast^ — its evolution .-....-. 34 Osteoblasts assuming their mature form inside cartilage capsules - 37 Osteoblasts free in pockets in midst of cartlage - - - . 38, 39 Osteoblasts in mature form -------- 43 Osteoblasts embedding themselves in ossein ----- 47 Osteoblasts may free themselves from ossein ----- 47 Osteoblasts may evolve into bone in either of two ways - - - 47 Osteoblasts becoming incorporated into osseous trabeculae - - 57-58 Osteoblasts passing directly into bone ------ 56 Osteoblasts forming into dense bone ------ 58 Osteoblasts embedded in ossein (Haversian system developing) - 66 Osteoblasts being set free from cartilage capsules - . - - 08, 69 Osteoblasts assume role of bone cell - - - - - - 76 Osteoblasts pavement trabeculae - - - - - - - 76 Osteoblasts do not grow from blood vessels - - - - - 81 P. Part played by blood in the evolution of bone - ■ - - 77 Pathological conditions affecting growth of antler - - - - 25 Preparation in skull and pedicle for growth of new antler - - 6 Preparations for shedding of antler appears at birth of new antler - 82 Process of shedding commences at level of corona - - - - 83 INDEX 109 R. PAGE Red deer — abnormal antlers 30-32 Red deer — Cervus E'.aphus — section antler about to shed - - llj-17 S. Section of sprouting antler ........ 9 Section of Fallow deer antler, pedicle and skuU, antler 2 3rd grown — eight weeks after shedding - - . - . - - 14 4Section of Red deer antler about to shed (showing portion of skull, pedicle and cerebral cavity) . - - - - - - I'J Section of hair bulb and glands in velvet ..... 22 Section of dog's epijihysis — for comparison - - - - ■ H Separation of antler from pedicle ....... 85 Shedding of the antler .... - - . - 82 Specimens of antlers beginning to grow ------ 28 Sprouting antlers. Red deer (Cervus Elaphus) - - - - - 7 Stratum lucidum in velvet covering antler - . . . - 14 V. Vascularisation of cartilage ........ 78 Vascularisation of the antler ..-..--- 80 Velvet — blood vessels of- - - - - - - - - 11 Velvet — cutis covering antler - - - - - - - - 1(1 Velvet — Histological development of . - - - - - lo W. Wapiti — C'ervus Canadensis, head of - • - - ■ ■ 4 PHINIKD A L THE UNIVEKsnv FRESS BY KUBEBT MACLEHO^K AND ■11 'i''"! II rw'\ , ; ,11* ' I \\k I , I'll ' I I ' ii ' I ' r 1 I I' ,1,1 S'ri'lli!"! 1 Jll i'!|' I li [iV Ujt,ll[ ! [ Mi , 'i'l I I /,!':'i;;.''i.vi|i ' ' '!',"„ I 1 II <' ' I I ( I I II ■.,i.\''J;;' ' ' .,1 ■L,,i I JW.., ,,,i,!,i.j, i,„. ii' 1