174 The Development of the Interstitial Cells of Leydig 



is a mesench}anal structure differing in no essential from the mesenchyme 

 in general. 



During the next succeeding stages a number of interesting changes 

 may be noted. The Leydig's cells undergo rapid increase both in num- 

 ber and size, so that they soon come to be the predominating constituent 

 of the intertubular spaces. The fixed connective-tissue nuclei, on the 

 other hand, become smaller and relatively much less numerous. The 

 increase in the number of the Leydig's cells is due, in large measure, to 

 karyokinesis, as mitoses are fairly abundant; but doubtless it is also 

 due, in part, to the continued conversion of mesenchyme cells into 

 Leydig's cells. These cells now begin to assume a fairly typical form; 

 the majority of them are polygonal, and the nucleus, spherical in shape 

 and eccentric in position, contains much chromatin and a large nucleolus. 

 Various other shapes, however, are observed which seem to be due to 

 mechanical conditions. Occasionally they are arranged alongside the 

 tubules, so that the latter in cross section appear surrounded by a sheath 



of Leydig's cells outside of 

 the basement membrane. 

 Soon after they are first seen 

 in the more central intertub- 

 ular spaces they begin to 

 make their appearance under 

 the albuginea, where they 

 rapidly increase, particularly 

 large masses being found 

 along the points of attach- 

 ment of the septa. During 

 this time also the branches 

 begin to disappear, and soon 

 there is no evidence of a 

 syncytial arrangement. This 

 change seems to occur last in 

 the subalbugineal cells; quite 

 a marked branching can 

 sometimes l)e made out in this 

 situation in even as late a 

 stage as the embryo of 3.5 cm. 

 At the stage of 3.5 cm. (Fig. 3) the Leydig's cells present the greatest 

 size to which they attain in the early embryo, and are very striking ob- 

 jects in preparations made by Mallory's method, which can be used so 

 as to give a fair differential stain. They are very granular, and the 



Fig. 3. Pig 3.5 cm. A group of Ley- 

 dig's cells from just beneath the albuginea. A 

 delicate reticulum is forming-. C.B., centro- 

 sphere B.. ; Mallory's connective-tissue stain. 

 X 800 . 



