The Effects of Thyroidectomy upon the Mammalian Pituitary 283 



of the lobe, but occupy the thin anterior or post-optic lamina, with the under 

 surface of which the cells of the tongue-like process of pars intermedia are 

 closely associated. Changes in the ependyma and neuroglia cells are most 

 noticeable in this region. 



In the cats operated upon nervous symptoms followed within twenty-four 

 hours after removal of the thyroids (and parathyroids), and the animals 

 were killed from four to six days after the operation. In the pituitaries of 

 these animals there is comparatively little change. Colloid is still present 

 in the spaces in the pars intermedia' in which it is normally found. Varia- 

 tions in the amount of colloid in the pituitary of the healthy animal are 

 80 great that no change can be definitely asserted, but the amount of colloid 

 in the pituitaries of these recently thyroidectomised animals is not un- 

 usually large. The granular bodies and hyaline material in the posterior 

 lobe are more plentiful than is normally the case. Accumulations of colloid 

 cells are seen in numerous places immediately beneath the ependyma cells 

 both in the body and neck of the posterior lobe. They form papular pro- 

 jections of the ependymal surface, and the contents are frequently seen 

 escaping into the infundibular cavity. Localised proliferations of ependyma 

 or neuroglia cells are also found. The changes, as in the rabbit's pituitary, 

 are not confined to the body and neck of the posterior lobe, but extend 

 into the anterior and posterior laminai. They correspond in extent and 

 distribution with the presence of cells of the pars intermedia lying outside 

 the nervous part. There is no accumulation of colloid inside the epithelial 

 cleft. 



In the only dog as yet operated upon the thyroids (and parathyroids) 

 were completely removed, and no symptoms occurred until five days after- 

 wards, when the animal had attacks of tetany. It recovered, but tetan}^ 

 again developed and extreme weakness came on. The dog was killed nine- 

 teen days after the operation. The anterior lobe of the pituitary shows 

 no change. There are no cystic accumulations of colloid in the pars inter- 

 media, but a great formation of colloid is taking place at the junction 

 between pars intermedia and pars nervosa. The nervous substance of the 

 posterior lobe is granular in appearance, and contains masses of colloid 

 accumulated in certain situations. It is most abundant in the neck of the 

 lobe and at the lower end of the infundibular recess. In places the 

 epend\nna lining is distended by colloid, some of which bursts through into 

 the infundibular cavity. Here again most of the colloid is cellular, and when 

 it mixes with the cerebro-spinal fiuid it takes the form of large nucleated 

 cells full of granular or amorphous material. 



In the neck of the lobe appearances are seen of which fig. 3. Plate II., 

 presents an illustration. Cells of the pars intermedia pass inwards invading 

 the nervous substance and frequently accompanying blood-vessels. As they 

 approach the infundibular cavity the cells become swollen and look like 

 colloid masses. They accumulate below the ependyma and finally pass 

 into the cavitv either in a cellular form or as a hvaline debri.s. 



