282 ' Herring 



occupied in its upper portion by a ' colloid-like (? plasmatic) material which 

 is not bounded by a cell membrane." 



In a previous paper (3), histological evidence has been brought forward 

 to prove that the posterior lobe of the pituitary furnishes a secretion which 

 passes through the nervous portion to enter the infundibulum and ventricles 

 of the brain. The secretion has normally a colloid appearance, and is prob- 

 ably a product of the cells of the pars intermedia. The results which 

 follow thyroidectoni}" furnish additional and strong evidence in favour of 

 this view. 



My observations have up to the present been confined to rabbits, cats, 

 and one dog. Three rabbits, of which the thyroids had been completely re- 

 moved, were placed at mj'- disposal by Professor S chafer. These animals 

 showed no symptoms, and were apparently healthy when killed three months 

 after thyroidectomy. The pituitary bodies were removed along with 

 part of the brain, fixed in Flemming's fluid, and cut in serial sections. Un- 

 fortunately, during the process of removal the posterior lobe of one animal 

 was badly injured, and was not available for examination. In the other 

 two there is no apparent change in the anterior lobe. Clear cells, deeply 

 granular cells, and transitional forms are present, and there is no evidence 

 of colloid production by them. 



The cells of the pars intermedia are distributed as usual, but are some- 

 what increased in amount, and stain more deeply. Remarkable changes 

 are at once apparent in the posterior lobe, and especially in that portion of 

 it which lies next to the pars intermedia. Masses of a colloid nature lie 

 among the cells and fibres of the pars nervosa (Plate I., fig. 1), and extend 

 forwards and upwards into the neck of the lobe right up to the floor of the 

 third ventricle. Some of this material is irregular in outline, and appears 

 to lie in lymph spaces, but much of it is cellular. The presence of a swollen 

 nucleus occupying the centre of a mass is frequently seen, and in some cases 

 instead of the hyaline or colloid appearance distinct granules are evident. 

 The granular cells and hyaline masses can be traced into the pars inter- 

 media, from the cells of which they apparently take origin. 



In the neck of the posterior lobe the colloid is even more plentiful ; 

 approaching the floor of the third ventricle it becomes more cellular in 

 appeai'ance. Many of the cells in this situation are extremely vacuolated, 

 others are granular or filled with an amorphous material. In the infundi- 

 bular recess at the floor of the third ventricle are found numerous cells of 

 varying size and masses of granular and amorphous material. The cells lie 

 free in the cavity of the third ventricle (Plate I., fig. 2), having found their 

 way out of the neck of the posterior lobe b}^ passing between the ependyma 

 cells. After their escape into the cerebro-spinal fluid they become swollen 

 and disintegrate with the production of a granular and amorphous debris. 



In addition to this increased production of colloid, there is a distinct 

 budding of the ependj-ma cells which line the ventricle, and a proliferation of 

 the adjacent neuroglia. The colloid bodies are not only present in the neck 



