174 INTERNAL SECRETIONS 



cells are a "secondary" sexual character genetically dependent 

 upon the interstitial cells. This may seem at first sight wholly 

 inacceptable. But there are some facts which support this 

 view. Ancel and Bouin stated that the interstitial cells in the 

 embryo of the pig are present before spermatogenesis begins. 

 The interstitial cells in the embryo of 30 mm. can be recognised 

 with certainty. Bouin records having observed signs of 

 secretory activity in the interstitial cells during embryonic 

 development (1903 c). In view of these facts Bouin and Ancel 

 (1903 d) suggested that the interstitial cells determine in some 

 measure the sex of the generative cells. In accordance with 

 Bouin and Ancel one might suppose that the cyclic spermato- 

 genesis under the influence of the increased or hypertrophied 

 interstitial cells occurring before heat is nothing else than the 

 recapitulation of what happens during embryonic life. The 

 suggestion of Bouin and Ancel has lately been supported by 

 Witschi (1921), who made observations on the frog. There has 

 been much discussion about a so-called "trophic" function, 

 the suggestion being that the interstitial cells prepare some 

 kind of material necessary for the nutrition of the spermatic 

 cells. This view is supported by many histologists, especially 

 by Plato, Kyvle (1911), Winiwarter, and recently by Kohn 

 (1914 a, 1920). Kyrle expressed the belief that the increase 

 of the interstitial cells in the neighbourhood of degenerated 

 tubules (or backwardly developed tubules, as I should prefer 

 to say) indicates that the interstitial cells have something to do 

 with the regeneration process which occurs in these tubules. 

 Such an assumption is in reality not very different from what 

 Bouin and x\ncel suggested. But no sufficient proofs exist for 

 this assumption, although some histologists claim that it is 

 definitely proved that the interstitial cells are no more than a 

 trophic organ in relation to the seminiferous tubules. It may 

 be useful to compare what such a critical histologist as Alfred 

 Kohn pointed out about this question. He claimed in 1914 that 

 there is " absolutely no proof " and that it is very "improbable " 

 that the interstitial cells of the testicle should be necessary for 

 the development of the seminiferous tubules. Later (1920), 

 without any new fact having been added, the same author 

 declared that the interstitial cells are probabfy a "trophic" 

 apparatus for the generative part of the testicle. Quoting 

 these two contradictory passages from Kohn, I should like to 



