170 The Development of the Interstitial Cells of Leydig 



Among recent text-books of histology, Boehm and Davidoff state that 

 Leydig's cells " are probably remains of the Wolffian body " ; Szymo- 

 nowicz says that we mnst assume that they are connective tissue. 



Thus it appears that there are two principal views as to the histological 

 nature of Leydig's cells. According to the one, they belong to the 

 connective tissues (Leydig, Koelliker, v. Ebner, Hofmeister, Hanse- 

 mann, Plato) ; according to the other, they are epithelial cells derived 

 from the germinal epithelium (Nussbaum, v. Bardeleben, v. Lenhossek). 

 It also appears that these views are, in the main, deductions from the 

 study of adult conditions. It is worthy of note that the two investi- 

 gators who have made a special study of the subject in mammalian 

 embryos, Hofmeister and Plato, both conclude that Leydig's cells are 

 derived from the interstitial tissue of the primitive testis. Their inves- 

 tigations, however, are incomplete, in that they were not made upon a 

 series of embryos extending into the early stages, but upon a few 

 isolated examples in the later stages of development. 



As my work upon this subject was nearing its completion, there ap- 

 peared a preliminary account of a study of the embryology of the ovary 

 and testis by Bennet M. Allen,' carried out upon pig and rabbit embryos, 

 in which the following statements are made concerning the interstitial 

 cells : " The connective-tissue elements of ovary and testis are derived 

 from the peritoneum. In early stages they 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 . . . the albuginea is 

 largely formed by the actual transformation of the basal parts of the 

 sex-cords into connective-tissue elements. The interstitial cells are char- 

 acterized by a large nucleus, distinct cell-boundaries, a centrosome and 

 centrosphere, and very granular cytoplasm. They first appear in the 

 stroma of both ovary and testis of the pig of 2.5 cm. length. They are 

 far more numerous in the testis than in the ovary. Their appearance 

 is coincident with that of a large number of fatty globules in the peri- 

 toneum and sex-cords. In the testis they persist for a long time. . . . 

 In both organs they divide by mitosis. This process soon ceases in the 

 ovary, while in the testis, on the other hand, division figures are found 

 in the interstitial cells at a stage as late as the 7.5 cm. embryo. In the 

 testis of the 15 cm. embryo they (the interstitial cells) have begun to 

 degenerate. This process manifests itself in a shrinkage of the cyto- 



" The Embryonic Development of the Ovary and Testis of the Mammalia. 

 Biological Bulletin of the Marine Biological Laboratory, Woods Holl, Mass., 

 Vol. V, No. 1. 



