SEX-COKDS AND SPERMATOGONIA IN CHICK 403 



;iii(l is very far from resembling the large cavity pictm-ed by 

 Semon ('87) in stages of about this age. 



THE INTERSTITIAL CELLS AND THE MITOCHONDRIAL CRESCENT 

 OF THE SPERMATOGONIUM 



It is not possible to enter into any account of the various 

 opinions which have been advanced and held as regards the ori- 

 gin of the interstitial cells of the testis. For the various theories 

 on this subject the reader is referred to Sainmont's article which 

 appeared in 1905. However, to give a slight historical back- 

 ground a few leading articles will be cited. 



Tourneux (79) identified the interstitial cells in the testes of 

 various animals and described them as being differentiated con- 

 nective tissue cells. 



Niissbaum ('80) thought that the interstitial cells were de- 

 rived from cell columns, which were given off by the germinal 

 epithelium in early embryonic history. 



Plato ('97) described the different stages which exist between 

 the connective tissue cells and the differentiated interstitial 

 cells. He studied the question in the testes of the cat and vari- 

 ous other animals. In connection with this work he brought 

 forward a rather novel theory which ascribed a nourishing func- 

 tion to the interstitial cells. He beheved that they manufac- 

 tured fat, which was passed through the basement membrane 

 of the seminiferous tubule into the cells of Sertoli and used as 

 food in spermatogenesis. 



Allen ('03) and Whitehead ('04) believed that the connective 

 tissue elements of both testis and ovary of the pig and rabbit, 

 from which the interstitial cells were differentiated were de- 

 rived from the peritoneum. Allen says: "In early stages they 

 (the connective tissue elements) are not distinguishable from the 

 cells which make up the sex-cords, except that the latter are 

 marked off from the stroma by their membrana propria." 



Whitehead "found himself in accord with the conclusion of 

 Allen, that the mterstitial tissue of the testis is derived from 

 the peritoneum, meaning thereby the mesothelium of the genital 

 ridge." 



