274 



Herring 



be absent. G antes further remarks that the presence or absence of the 

 saccus vasculosus brings about Jno modification of the nervous lobe. It is 

 very probable that the saccus vasculosus has, as Gentes believes, a function 

 similar to that of a choroid plexus. 



The Pituitaky Body of Elasmobraxchs. 



Histological Features. 



The pituitary body of the skate — Raja batis — is taken as the type. In 

 the skate the pituitary is a long, club-shaped body which lies for the most 

 part behind the small lobi inferiores. Its anterior extremity is thin, and 

 stretches forward to the optic chiasma. Close to it is the large saccus vas- 

 culosus which is bilobed. The lobes of the saccus vasculosus appear to arise 

 just above the anterior part of the pituitary by a common origin with it. 



Fig. 6. — Effect of the injection into the jugular of a cat of fi c.c. of an extract of the 



saccus vasculosus of the cod. (12 glands in 20 c.c. Ringer.) 



The effect upon the kidney is no greater than that produced by rapid injection of 5 c.c. Ringer alone. 



Each lobe passes backwards and outwards, and the body of the pituitary 

 lies between them. A fine prolongation of connective tissue passes from 

 the under surface of the pituitary body into the cartilage of the floor of the 

 cranium, binding it closely down to the latter. This is the remnant of the 

 neck of Rathke's pouch, from which the pituitary is developed, and was de- 

 scribed by Miclucho-Maclay (6) in the shark. In the skate all connection 

 between buccal mucosa and pituitary body is lost, but a string of connective 

 tissue persists in the cartilage. It is advisable for this reason, in removing 

 the pituitary body, to expose it by cutting away the cartilage of the floor 

 of the cranial cavity. 



On making a sagittal section through the pituitary, it is seen to extend 

 for a long distance backwards from the optic chiasma, and to be quite dif- 

 ferent in structure from the pituitary bodies of mammals, birds, and teleosts. 

 The main body of the organ lies posteriorly, and is the part which Haller 

 designates as the head of the pituitary. It at first sight appears to be com- 

 posed of tubules lined by large columnar cells, but on careful examination 



