216 CONNECTIVE TISSUE. 



difficult to convince oneself that the character of the cartilaginous 

 basis-substance, whether hyaline, striated, or fibrous, depends 

 upon the shape and the grouping of the original, indifferent 

 medullary corpuscles alone. 



The cartilaginous callus, obtained after subcutaneous fract- 

 ures of the leg-bones of dogs and cats, I found very suitable for 

 the study of the development of cartilage. Here the new forma- 

 tion of cartilage arises from nests, identical with medullary 

 spaces, which in their center contain blood-vessels, at their 

 periphery spindle-shaped elements, as the result of the inflamma- 

 tory new formation. The medullary elements close around the 

 blood-vessel* are globular, and are succeeded by layers of spindle- 

 shaped bodies, the nuclei of which are partly faded, indicating 

 that these formations are in the stage of transition from a uni- 

 form granulation into the stage of infiltration with glue-yielding 

 basis-substance. In such inflammatory nests, also, we observe 

 the transformation of capillary blood-vessels into solid strings, 

 and afterward into small medullary elements. The process is 

 the same as in the involution of bone-tissue, due to normal senile 

 changes. In the same cartilaginous callus we also encounter 

 numerous nests in which red blood-corpuscles and blood-vessels 

 arise from cartilage corpuscles (see page 98), and these forma- 

 tions precede the liquefaction of the calcified cartilaginous basis- 

 substance, which occurs previously to the production of new 

 medullary tissue and of bone. 



The embryonal or medullary elements are, under all circum- 

 stances, the formers of tissue. Those from which bone arises 

 have been termed " osteoblasts " by Gegenbaur, who considered 

 them to be, specifically and exclusively, bone-formers. We are 

 far from understanding the specific nature and limits of embry- 

 onal corpuscles, and the designation "osteoblasts" is therefore 

 superfluous. We might with equal propriety speak of " periosto- 

 blasts," " chondroblasts," etc., while, in fact, all these tissues 

 originate from one and the same source namely, the medullary 

 tissue. What character the territory will assume, what will be 

 the nature of the basis-substance in the territory, depends upon 

 the grouping of these many-named " blasts " in the stage of indif- 

 ference preceding the new formation of a tissue. 



In 1873, I admitted the possibility that, under certain physio- 

 logical conditions and changes, one variety of basis-substance 

 might be directly transformed into another ; periosteum, f . i., into 

 bone or into cartilage, hyaline into striated cartilage, etc. This 



