250 MANUAL OF HISTOLOGY. 



time that we do not wish to deny its significance in the processes of nutri- 

 tion taking place in bone. 



REMARKS 1 On this experiment, performed in the last century by Duhamcl, 

 comp. Flourens (Annal. de Scien. Nat., 2 serie, tome 13, p. 97). 2. Goodsir (Anatomi- 

 cal aiid Pathological Researches, Edinburgh, 1845, p. 66). 



Osseous tissue, as has been already mentioned, is not one of the primary 

 formations ; it belongs rather to those appearing late in the human body, 

 and is missing at a period in which the development of most of the 

 remaining tissues is far advanced. 



Its nature is consequently quite different from that of cartilage, whose 

 place it is destined to take to a great extent. For the rest, this tissue is 

 developed within very different spaces of time in the various localities of 

 the body. 



Its origin, or the theory of the process of ossification, is one of the 

 most difficult chapters of histology, and one in regard to which there is 

 the greatest variety of opinion at the present day. 



Now, in that all the bones of the skeleton are moulded first in cartilage, 

 with the exception of some of those of the head, and that this substance 

 appears to the unaided eye to be transformed into osseous tissue, nothing 

 could be more natural than the idea that this actually took place, that 

 bony masses were developed by a transformation of cartilage, a view which 

 was held by microscopic histologists even until comparatively recently. 



But the investigations of Sharpey, Bruch, Baur, and H. Mutter, soon 

 made it clear that this older theory is incorrect, that the carti- 

 laginous mass may undergo calcification, but does not generally become 

 bony tissue, dissolving rather, and so making room, for the advancing 

 formation of bone (p. 172). The latter always comes about in a simple 

 way. New generations of stellate cells make their appearance in a 

 ground-substance, at first soft, and soon becoming diffusely calcified, 

 representing thus osseous tissue. 



REMARKS. For a very long time endeavours were made to elucidate, by means of 

 the microscope, the manner in which this metamorphosis of the non- vascular non- 

 laminated cartilage, containing round cells, could take place into laminated bone 

 with its stellate cells, and especially the mode of transition of the latter elements of 

 cartilage into those of bone. In the history of this branch of science we find three 

 different views as regards the last point, springing up one after another, and taking 

 the field against each other. According to one of these, the nucleus of a cartilage 

 cavity spreads out and becomes stellate, forming thus a bone corpuscle. From the 

 second theory we gather that the whole cartilage cell undergoes this transformation. 

 A third view, which appeared for a time to reign supreme, originated with Schwann 

 and Herilc. According to it, the bone-corpuscle is formed by an uneven thickening 

 of the wall of the capsule of the cartilage cell. Indeed, the appearance of stellate, 

 shrunken, true cartilage cells within their capsules, as well as the cellular nature of 

 the bone-corpuscle by Virchow, seemed to give weight to this theory. Koellikers 

 discoveries also of the nature of rachitic bone supported it likewise. But in the 

 year 1846, Sharpey (Quain's Anatomy, fifth edit., by Quain and Sharpey, part 2, 

 p. 146, Lond., 1846), and shortly after him Koelliker, declared that true bone takes 

 its origin in the human being and vertebrates also from connective-tissue substrata 

 of a membranous nature, explaining first of all the growth of bone from the 

 periosteum, and next that of a number of osseous structures not previously laid down 

 in cartilage, the so-called secondary formations. Thus it was that two modes of 

 origin of osseous tissue were supposed to exist by many, first, by a transformation of 

 cartilage already present ; and again, by the metamorphosis of a substratum of con- 

 nective-tissue, although Sharpey maintained the latter mode of origin to be exclusively 

 that also of the bones even previously moulded in cartilage. The following is an 



