CONNECTIVE TISSUE. 



253 



assuming, as is generally done, that a division of cartilage corpuscles takes 

 place, it would be better to hold that, in the protoplasma set free by liquefac- 

 tion of the basis-substance, there is at certain intervals a new formation of 

 living matter, which results in the formation of the compact, glistening lumps. 

 The multinuclear protoplasmic bodies, the " myelopaxes," according to this 

 view, are simply freed territories of the cartilage tissue, and we can easily 

 understand that occasionally a number of such territories coalesce into a 

 common layer, before a further differentiation occurs. 



Unquestionably, the cartilage tissue is directly transformed into medullary 

 tissue. The question how bone-tissue arises from medullary tissue is answered 

 by the careful study of places where newly formed bone is closely attached to 

 calcined cartilage. Here we notice a regular layer of finely granular psteoblasts 



FIG. 104. KNEE-JOINT CAETILAGE OF A YOUNG CHICKEN, CLOSE TO THE 

 BORDER OF OSSIFICATION. HORIZONTAL SECTION. CHROMIC ACID SPECI- 

 MEN. 



C, calcified frame of basis-substance of hyaline cartilage ; H, zone from which the lime-salts 

 have been dissolved ; M, newly formed medullary space. Magnified 700 diameters. 



between the decalcified basis-substance of cartilage and the newly formed 

 bone. We can also trace every transition of free, uninfiltrated osteoblasts 

 from the first steps till they finally fade in the basis-substance. The delicate 

 granulation of the new osteogeneous basis-substance indicates that in the 

 formation of bone the structure of the osteoblasts has not been completely 

 lost. 



The bone of birds is essentially constructed like that of mammals. We 

 find systems of lamellae around vascular canals ; we also find in the cavities 

 of the basis-substance the bone-corpuscles, with their characteristic stellate 

 offshoots. How far the presence of living matter within the basis-substance 

 of the bones of birds corresponds with that of the mammal, further researches 

 must reveal. 



