INTERSTITIAL CELLS OF THE CHICKEN TESTIS. 143 



agents being used especially because the internal secretion of 

 the testis has usually been described as appearing in the form 

 of fat or oil drops in the cells. 



For comparison with these, I have studied the testes of four- 

 teen older birds, ranging from 5 to 12 months in age. These were 

 all but three pure Barred Plymouth Rocks, one was a White 

 Leghorn, and two were cross-breds. They were killed at differ- 

 ent times of year, October, November, January, March and 

 April. In birds over six months of age, dividing germ cells were 

 found, all stages from spermatogonia to spermatozoa. The 

 testes from six of these birds had been put up previously for 

 other purposes for which the best cytological methods were not 

 necessary, but the general observations on these accord so well 

 with those on the very best fixed material, that I do not hesitate 

 to state that my observations cover fourteen birds. The other 

 eight testes were cut in small pieces and fixed in Gilson, Flemming 

 and Hermann. With two birds, every possible precaution to 

 secure absolutely normal fixation was taken: the testis was 

 removed from the living bird and put directly into Flemming, 

 heated to the temperature of the bird's body, and the testis 

 was then cut into thin slices with a razor, as it was held in the 

 hot Flemming. 



The ordinary method of clearing in xylol for embedding and 

 mounting was not used with all of the material, as xylol dis- 

 solves fat. From Mallory and Wright's "Pathological Tech- 

 nique," I found that chloroform and clove oil do not dissolve 

 fat fixed in osmic acid, so by clearing the Flemming material 

 in chloroform or clove oil, and mounting the sections in chloro- 

 form balsam, I got preparations showing fat. 



OBSERVATIONS. 



In sections of the just-hatched testis, one can see without 

 great magnification that about half the substance is interstitial 

 connective tissue (Fig. i). The seminal tubules are small and 

 far apart. Careful detailed study shows that the cells of the 

 seminal tubules have comparatively large round nuclei, with a 

 linin network and scattered chromatin granules; in fact, they 

 are typical resting germ cells. There were no signs of any 



