392 INTERNAL SECRETION 



with, but subsequent to, its external secretory function. Prenant 

 (1898), and later Born and Fraenkel, recognized that both in 

 genesis and structure the corpus luteum, which persists after the 

 ejection of the ovum and is of epithelial origin, possesses the 

 characteristics of an internal secretory gland. Later on, another 

 ovarian tissue formation of connective tissue origin, which had 

 long been known to histologists, but was first minutely investi- 

 gated by Limon (1902), was recognized by Bouin as possessing 

 internal secretory functions. 



In describing the secretory elements in detail, it is expedient 

 that the male and female glands should be treated separately. 



Testis. The germinative portions of the testicle are the semi- 

 niferous tubules which, in addition to the spermatic cells (sperma- 

 togonia, spermatocytes, spermatides and sperma), also contain 

 the syncytium of Sertoli's cells. In addition to these, however, 

 the testis of all mammals contains peculiar elementary constituents 

 which are known as " interstitial " cells or " Leydig's between- 

 cells." These cells have formed the subject of repeated investi- 

 gation and it has been shown that they are characterized by 

 special genetic and structural features. They are of mesodermal 

 origin and appear in the primitive genital trace at a very early 

 phase of embryonal development, before the seminal cells have 

 assumed their cytological character. Enclosed in the cytoplasm 

 of Leydig's cells are granules which stain with osmium and 

 haematoxylin-copper-lake (Regaud), acidophile and basophile 

 granules, pigment granules, and peculiar cell-crystals; and these 

 enclosures give them a structural resemblance to secreting gland- 

 cells. Leydig's cells are situated in the interstitial tissue be- 

 tween the seminiferous tubules ; they are sometimes few in num- 

 ber, but they may be present in extensive clusters, especially 

 where, owing to lack of development or atrophy of the semi- 

 niferous tubules, there is room for fission to take place. 



These between-cells were universally regarded as trophic 

 tissue elements, whose function it was to take up nutrient material 

 from the blood-vessels, and pass it on to the Sertoli's cells. This 

 theory received fresh support from the discovery by Regaud 

 (1901) that a substance passes from Leydig's cells to Sertoli's 

 cells. Reinke, however, who had proved that the cell crystalloid 

 discovered by him in the human testis passes into the capillary 

 lymphatics, suggested as early as 1896 that Leydig's cells might 

 elaborate an internal secretion which plays an important part in 

 the production of sexual instinct. Regaud and Policard, Loisel, 

 Mosselmann and Rubay also ascribed the internal secretory 

 function of the testis to this tissue element, but Bouin and Ancel 

 were the first to describe this tissue as the " glande inter stitielle 

 du testicule." In a large number of publications (1903-1904), 

 these latter authors brought forward the proofs in support of their 

 hypothesis, that this interstitial gland performs all the functions 



