PROBLEMS OF MODERN SCIENCE 



which cartilage is nourished is not properly under- 

 stood, and awaits explanation. 



The growth and expansion of cartilage is 

 apparently a simple process. The cartilage cell 

 periodically divides into two. Each of the two 

 resulting daughter-cells vigorously manufactures 

 embedding material, exuding it, as it were, all 

 round itself, and thus becomes separated from its 

 twin sister. Subsequently each daughter-cell will 

 in its turn divide, giving rise to two new cells, 

 and thus the process goes on. As many cells are 

 similarly engaged, the cartilage grows and expands, 

 each new cell adding its quota to the whole. 



There comes a time when, at one definite spot 

 situated at about the middle of the cartilaginous 

 miniature of the future thigh-bone, the cartilage 

 sickens and dies. This is the only possible inter- 

 pretation of the peculiar appearances presented 

 by the cartilage, and in very truth death first lays 

 his finger upon us before we are born. 



The dying cartilage is invaded from without 

 by a veritable army of cells which practically eat 

 their way in. This statement, simple though it 

 appears, is pregnant with interest. One is apt to 

 regard all the tissues of the body as working 

 harmoniously together for the common good, 

 every group of cells in its allotted place con- 

 cerned in its allotted task. This, however, is not 

 absolutely true. There is evidence to show that 

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