332 Kojirna 



nuclei generally are larger than usual (5a to 7*5/i). They contain abund- 

 ance of coarse chromatin granules and stain more deeph' than normally 

 with hematoxylin. The oxyphil cells are far fewer in number than in the 

 normal gland, and are smaller in size : their cytoplasm is compact. Scattered 

 about in the pars anterior are numerous vesicles occupied by hyaline sub- 

 stance, which is almost everywhere remarkably increased in quantity. The 

 nuclei of the cells of the pars intermedia are also more deeply stained 

 than usual by hsematoxylin. The pars posterior appears more compact 

 than in the normal gland : it shows abundance of hyaline droplets. 



The above changes are rather better marked with potassium iodide than 

 with sodium iodide. 



Summary of Observations on the Rat. 



1. The microscopic appearances of the several parts of the normal rat's 

 pituitary are described, with especial reference to the characters of the 

 dili'erent kinds of cells they contain. 



2. The result of total thyroidectomy is to produce the appearance within 

 the pars anterior of a number of large swollen cells wnth vacuolated proto- 

 plasm, as well as a considerable increase of hyaline substance which is for 

 the most part contained w^ithin vesicles in this part of the gland. The 

 pars intermedia is thickened. In the rat I have not observed the increased 

 discharge of hyaline substance through the pars nervosa described by 

 Herring in the dog, cat, and rabbit. 



3. The result of parathyroidectomj^ is to produce the appearance of a 

 few similar swollen cells; but the effect is far less than after thyroid- 

 ectomy. The cells of the pars intermedia become enlarged. 



4. Castration in male rats is followed by the production of a large 

 number of swollen cells in the pars anterior. The appearance of the cyto- 

 plasm in these cells is very like that seen after thyroidectomy and para- 

 thyroidectomy. But the outlines of the cells are indistinct, and their 

 nuclei are much larger and contain tine chromatin granules ; some of them 

 show an appearance suggestive of degeneration. The cells of the pars 

 intermedia are also eularu-ed and sw^ollen. 



5. The addition of thyroid substance to the ordinary diet of normal rats 

 causes at first diminution of the oxyphil cells in the pituitary body and 

 accumulation of hyaline substance both in the intraglandular cleft and in 

 the pars posterior. If the thyroid feeding is prolonged the number of 

 oxyphil cells again increases : this is also seen if parathyroid is substituted 

 in the diet for thyroid. In thyroid-fed, thyroidectomised, parathyroid- 

 ectomised, and castrated rats the changes caused by thyroid feeding are 

 still evident: indeed, there maj^ be an even greater amount of hyaline 

 substance produced within the gland. 



6. Feeding with anterior lobe of ox-pituitary causes an increase of 

 oxyphil cells in the pars anterior. 



7. Feeding with posterior lobe of ox-pituitary produces a large increase 



