336 SPECIAL HISTOLOGY. 



108. The vital phenomena exhibited in the mature bones are not, 

 during the vigorous period of life, accompanied with any notable or active 



been somewhat increased, as we think, by a want of perception among the combatants, of 

 the fact, that several totally distinct questions are involved. These questions seem to us to 

 be the following, and we shall endeavor to consider them in detail. 



1. Whether the tissue from which "secondary" bone proceeds is cartilage, or not? 



2. Whether it is morphologically homologous with cartilage, or not? 



3. Whether ossification takes place in it in the same manner as in cartilage, or not? 

 And as the result of the answering these : 4. Whether the differences between the two 



tissues are sufficient to constitute the basis of a classification of the bones or not? 



1. To answer this by saying with Meyer that every tissue which ossifies is cartilage, is 

 simply to beg the whole question. Cartilage we hold to be distinguished from 'indifferent 

 tissue, by the fact of its matrix containing chondrin. The substance which in the foetus con- 

 tains no chondrin, but will subsequently become a cartilage though in common parlance it 

 is very convenient to call it " foetal cartilage" is no more cartilage than the cartilaginous 

 basis of a future bone, which might just as properly be called fostal bone, is osseous tissue. 

 There can be no question then, we think, that Ko'lliker is in the right, as against Reichert, 

 Meyer, and others, when he says that secondary bone is not developed from cartilage, and 

 that, in this respect, it may be distinguished from primary bone. 



2. Though this matrix of secondary bone, however, is assuredly not cartilage, it is another 

 matter whether it is, or is not, morphologically homologous with cartilage. To arrive at any 

 just conclusion on this head, it is necessary to understand the precise structure of this tissue, 

 which Messrs. Tomes and De Morgan have been the first to point out : " If attention be 

 directed to the part furthest removed from the bone, it will be seen that the membrane-like 

 mass is composed of oval cells with slight prolongations from the extremities, which are 

 frequently arranged in the form of bands of fibrous tissue. Dr. Sharpey has observed that 

 the membrane into which the bone extends is like fibrous tissue in an early stage of develop- 

 ment; and this observation is strictly true when confined to the part indicated, but the 

 analogy ceases [?]as we extend our examination towards the bone. Here, in the place 

 of cells with elongated processes, or cells arranged in fibre-like lines, we find cells aggre- 

 gated into a mass, and so closely packed as to leave little room for intermediate tissue. The 

 cells appear to have increased in size at the cost of the processes which existed at an early 

 stage of development and formed a bond of union between them. Everywhere about growing 

 bone, a careful examination will reveal cells attached to its surface, while the surface of the 

 bone itself will present a series of similar bodies ossified. To those we propose to give the 

 name of osteal cells, as distinguished from lacunal and other cells. In microscopic characters, 

 the osteal cells closely resemble the granular cells of temporary cartilage ; so closely, indeed, 

 that the latter, when detached from the cartilage, could not well be distinguished from them. 

 They are, for the most part, spherical or oval in form, and lie on the surface of the growing 

 bone in a crowded mass, held together by an intervening and apparently structureless 

 matrix. Here and there we find a cell which has accumulated about itself an outer invest- 

 ment of transparent tissue, and has, in fact, become developed into a lacunal cell destined 

 to become a lacuna" (1. c. p. 23). 



The tissue, then, from which secondary bone immediately proceeds, is composed of a 

 homogeneous matrix, in which corpuscles, identical with the cartilage-corpuscles, are 

 imbedded: it is therefore identical, as Dr. Sharpey described it, with young connective 

 tissue; and as we have seen above (note, 101), and as the authors state, with foetal carti- 

 lage. Though not cartilage, therefore, it is homologous with it (as is, indeed, admitted by 

 Professor Koiiiker) ; a fact which is still more strongly evidenced by the transition of carti- 

 lage into a similar tissue, at its edges (Tomes andDe Morgan, 1. c. p. 24), which may readily 

 enough be observed, and which has been particularly shown by Reichert to occur between 

 the primary and secondary bones of the skull (" Zur Streitfrage fiber die Gebilde der Binde- 

 substanz, ober die Spiralfaser und iiber den Primordial-Schadel," Muller's " Archiv," 1S53). 



Now it seems to us that a tissue which is identical with the embryonic form of cartilage, 



