268 ' Herring 



injection to 42 drops in five minutes afterwards. Where the secretion is 

 very slow to begin with, the subsequent increase may be even more marked. 

 The secretion is independent of the increase of blood-pressure, as was noted 

 by Schafer and Herring in the case of extracts of the mammalian 

 posterior lobe ; it is, however, related to the expansion of the kidney, and 

 de;reases when that begins to pass off. 



A subsequent dose of the extract in the same animal, if administered 

 after the kidney and urine effect have passed off, is followed by a repetition 

 of the same changes, although there may be an initial fall of blood-pressure, 

 followed by a slow rise (fig. 3). 



Extracts of the posterior lobe of the fowl's pituitary have, therefore, an 

 effect on blood-pressure, kidney volume, and urine secretion which is very 

 similar to that produced by extracts of the posterior lobe of the mammalian 

 pituitary. It is impossible to determine whether the active principles in 

 the posterior lobe of the bird's pituitary are products of the epithelial cells 

 of the pars intermedia or are formed solely in the nervous substance. The 

 large preponderance of the latter in the bird might be considered as an 

 argument in favour of their nervous derivation ; but, on the other hand, if 

 the cells of the pars intermedia pour their secretion into the pars nervosa 

 of the lobe, it may accumulate there in larger quantities. There is evidence 

 in the mammalian pituitary that the secretion is emptied into the third 

 ventricle of the brain, and is furnished by the cells of the pars intermedia. 

 The posterior lobe of the bird's pituitary is so constituted that a similar 

 process may quite well be the normal one in it also. 



The Pituitary Body of Teleosts. 

 Histological Features. 



The pituitary body of the cod — Gadus morrhua — is taken as the type. 

 In this fish the pituitary is a prominent organ lying in front of and below 

 the lobi inferiores. The infundibular region is complicated by the presence 

 of a saccus vasculosus, which lies immediately behind the pituitary, between 

 the two large lobi inferiores. The pituitary body, although forming a single 

 organ, is seen to be composed of two different kinds of tissue, an anterior 

 portion, reddish or white according to the amount of blood in it, and 

 a posterior part, greyish in appearance. The two portions are directly 

 continuous with one another, and the line of division between them can only 

 be recognised by the change of colour in passing from one to the other. 

 On section, the pituitary is found to be a solid organ, and to resemble in 

 general structure the pituitary of mammals and birds ; it differs from these, 

 however, in the arrangement of its parts. 



In a median sagittal section (fig. 2 of Plate) the general relationship of the 

 different parts is readily appreciated. The pituitary is composed of three 

 varieties of tissue, two of which are epithelial and the third nervous, the 



