142 On the Interstitial Cells in Testicle of Guinea-Pig. 



(llii) Benda, "Bemerk. z. norm. u. patholog. Histol. der Zwischenzellen d. Menschen 



u. d. Saugetier," 'Archiv f. Frauenkunde,' vol. 7 (1921). 

 (11c) Schulz, Eugen, 'Ueber Umkehrbar Entwicklungs-prozesse,' Leipzig, 1908. 



(12) Kyrle, "Ueber d. Begenerationsvorgange im tier. u. menscH. Hoden.," ' Sitzungsber. 



Akad. d. Wissensch., Wien.,' vol. 120, III. Abt., 1911. 



(13) Kohn, " Der Bauplan d. Keimdr.," ' Arch. f. Entwicklungsmech,' vol. 47 (1920) ; 



Stieve, " Entwickl., Bau u. Bedeut. d. Keimdriisenzwischenzellen,'' ' Ergebn. d. 

 Anat. u. Entwicklgesch.,' vol. 23 (1921) ; Tiedje, " Unterbindungsversuche am 

 Hoden, unter besonderer Beriicksichtigung der Pubertatsdr.-frage/' 'Deutsche 

 Medizin. Wochenschr.,' 1921, No. 13. 



DESCEIPTION OF PLATES. 

 (The figures are drawn by Miss L. Lehberfc, Dorpat.) 



Plate 1. 



Fig. 1. — Two sections through the testicle of a normal animal aged about 4g months 

 (Prot. No. 27). On the left : interstitial cells in form of a triangle between 

 tubules in full spermatogenesis ; on the right : interstitial cells embedded 

 in a granular mass in the neighbourhood of blood-vessels. 



Fig. 2. — Two sections through the testicle of a normal animal about three weeks old 

 (Prot. No. 32). The interstitial cells are rich in protoplasm, the nucleus is 

 large. In the left half the interstitial cells are embedded in the granular 

 mass. 



Plate 2. 



Fig. 3. — Section through the upper testicular fragment of an animal subjected to the 

 " complex " testicular section (Prot. No. 76). The hypertrophy of the inter- 

 stitial cells is enormous. The seminiferous tubules with only one stratum of 

 cells (cells of Sertoli). 



Fig. 4. — Section through the testicle of an animal subjected to the operation described 

 in D (p. 138). (Prot. No. 72). The seminiferous tubules are in the juvenile 

 stage, although the animal was fully grown when operated on. The operation 

 was performed about four months previously. The number of interstitial 

 cells is very markedly increased. 



All the testicles or testicular fragments were fixed in the solution of Helly (solution 

 of Midler with 5 per cent, formol) and stained by eosin and hematoxylin. Only fig. 4 

 is made from a fragment fixed in Flemming and stained by Heidenhain's iron-alum 

 hematoxylin. All the preparations were made by Dr. Wagner. 



