﻿210 Proceedings of the Royal Physical Society. 



uterine life, the young mesoblastic cells which are placed 

 in the axes of the limbs are so crowded together that they 

 become condensed. This we may well believe leads to 

 difficulties in obtaining adequate nutrition, and in carrying 

 on the necessary processes of cell life, and so, conforming 

 to the laws of multiplication of living organisms, individual 

 adaptation is substituted for rapid genesis. The specialisa- 

 tion is in the direction of the formation of cartilage cells, 

 and by them the embryonal cartilage is formed. It is 

 beyond the limits of the present paper to discuss the 

 reason why these cells specialise as chondroblasts. 



The older cells of the embryonal cartilage, that is to 

 say, those situated about the centre of the bone shaft-to-be, 

 gradually, but progressively hypertrophy, and by their 

 hypertrophy mark histologically the centre of ossification. 

 The meaning and results of this hypertrophy are interesting. 

 The cells are in some measure specialised, and have, therefore, 

 according to the theory of growth lost, in part at least, 

 their power of genesis. Their hypertrophy tells us that 

 their anabolism is in excess of their requirements, that 

 their enviroament is favourable ; but it is too favourable, 

 and, unable to divide, they increase in size until the 

 nemesis of cell growth overtakes them, and they degenerate 

 and die, because their surface is too small to support the 

 contained mass. 



The matrix in the neighbourhood, unrefreshed by the 

 activity of the cells, degenerates, and lime salts are deposited 

 in it. This interpretation of the meaning of the calcifica- 

 tion of the cartilage matrix, brings it into line with the 

 pathological calcifications, " which occur almost without 

 exception in degenerating, dying, or dead tissue."^ This, 

 in terms of the theory of growth, is the meaning of the 

 histological fact that, " on acquiring their maximum growth 

 the cartilage cells soon exhibit indications of impaired 

 vitality, as suggested by their shrinking protoplasm and 

 degenerating nuclei." ^ As the chondroblasts die out, 



1 Hektoen and Reisman, Text-Book of Pathology. Saunders, 1901, p. 113. 

 ^ Piersol, loc, cit. 



