284 . Herring 



In this dog there are also marked changes in the ependyma cells, con- 

 sisting chiefly of a budding otl" of small round globules into the infundibulum 

 and third ventricle. Fig. 4, Plate II., is a photograph of part of the internal 

 surface of the posterior lamina, and shows the formation and liberation 

 of these small globular bodies. The ependyma cells of the infundibular 

 region are not ciliated, and probably have a secretory power. The com- 

 bined products of the cells of the pars intermedia and of the ependyma 

 cells are mixed, and form a considerable accumulation in the infundibular 

 recess of the third ventricle. The nature and signiticance of this material 

 is as yet undetermined ; its formation in thyroidectomised animals appears 

 to be an exaggerated condition of a normal process. 



Summary. 



Thyroidectomy is followed by definite histological changes in the 

 pituitary body. The anterior lobe is apparently unaffected ; it shows no 

 immediate sign of increased activity as far as can be judged from the 

 animals examined. Whether or not it undergoes an alteration in animals 

 which survive for a long time remains to be determined. 



There is increased activity of the cells of the pars intermedia, and 

 probably an increase in the number of these cells in animals which live 

 for some time after the operation. In this respect the work of Rogowitsch 

 and others is confirmed. 



The most striking changes are manifested in the nervous part of the 

 posterior lobe and in the laminae forming the floor of the third ventricle. 

 In these situations granular, hyaline, or colloid bodies become very 

 numerous. They appear to be, in part at least, of a cellular nature, and to 

 find their way between the ependyma cells into the infundibular recess 

 and ventricles of the brain. 



There are also alterations in the ependyma and neuroglia cells in the 

 same regions. The former appear to have a secretory function and give off 

 small clear globular bodies into the infundibular recess and third ventricle. 

 There are also localised proliferations of neuroglia. 



The significance of these changes is as yet undetermined. The colloid 

 bodies appear to arise from the epithelial cells of the pars intermedia, and 

 their extensive production to be an exaggeration of a normal process. Further 

 work is being carried on to determine the nature of the colloid of the 

 pituitary, its relations to the active principles found in the posterior lobe, 

 and its influence in the production or amelioration of the symptoms, which, 

 in many animals, follow removal or disease of the thyroid. 



The expenses incurred in this work are assisted by a grant from the 

 Carnegie endowment for research purposes. 



