38 LEO LOEB. 



guinea pig which consists principally of tubules with several 

 layers of epithelium which are in the process of spermatogenesis. 

 Between these tubules there is very little stroma with blood 

 vessels and a very small number of polygonal cells. 



Sections through the tissue, taken from the place where nor- 

 mally the uterus is situated, show fibrillar connective tissue in 

 which are situated nests composed of rather large polygonal, 

 cylindrical or ellipitical cells, the protoplasm of which stains well 

 with eosin. The nuclei of these cells are round vesicle with 

 chromatic particles distributed rather diffusely. These cells 

 form the matrix of the neighboring fibrillar connective tissue. 

 Through rarefaction of the cytoplasm and through a condensa- 

 tion, backing together of the nuclear chromatin these cells are 

 transformed into the surrounding connective tissue. We also 

 studied in microscopic sections the fat tissue which filled the 

 space between the undescended testicle and the kidney, without 

 finding any trace of further testicular or of ovarian tissue. 



Mammary Gland.- The nipples of the guinea pig were distinct 

 and we cut out pieces from the tissue where normally the mam- 

 mary gland is situated. In the male a few scattered ducts lined 

 by epithelium in which mitoses do not usually occur represent 

 the mammary gland. 1 In our case, a very much furthergoing 

 development of the mammary gland was found on microscopical 

 examination. Sections through one of the two mammary glands 

 showed solid tissue consisting of a large number of lobules of 

 mammary gland tissue, joined together by thin strands of 

 fibrous tissue. The whole gland was surrounded by fat. Each 

 lobule consisted of acini lined by cuboidal epithelium of medium 

 size. The nuclei were vesicular and relatively large. The 

 lumen of the acini varied in size and often contained some colloid 

 material or desquamated cells. Occasionally an acinus cell was 

 found to be vacuolar. In the stroma between the acini there 

 were numerous small connective tissue cells. At some places, 

 where the interstices between the acini were somewhat wider and 

 the stroma was slightly edematous, polynuclear leucocytes 

 staining deeply with eosin were found. The largest ducts were 



1 In the ducts of the mammary gland of a young male guinea pig, about 30 days 

 old, we encountered however one mitosis. v 



