270 ' Herring 



pituitary. It is freely invaded by cells of the pars intermedia — more so, 

 indeed, than is the case in mammals. It contains, moreover, the colloid or 

 liyaline bodies of mammals and birds, and like them it encloses an infundi- 

 bular cavity which communicates with the ventricles of the brain. The 

 pituitary of the cod furnishes another example of a brain gland similar 

 in its essential structure and relationships with the brain to the pituitary 

 of mannnals and birds. Pars intermedia — chromophobe portion of Sterzi — 

 and pars nervosa make up a structure strictly comparable to the posterior 

 lobe of mammalian and avine pituitaries. In the cod there is no epithelial 

 cleft, and anterior and posterior lobes are fused together. The fusion is in 

 some cases even more complete than is indicated in fig. 2 of Plate, for it not 

 infrequently happens that some of the chromophil cells of the anterior lobe 

 are found among the cells of the pars intermedia, and cells of the latter 

 occur in the true anterior lobe. It is almost impossible, for this reason, to 

 separate one portion from another exactly ; but the difference in colour of 

 the two parts is, as a rule, sufficiently obvious to enable one to divide them 

 for the purpose of making extracts. 



The saccus vasculosus of the cod is single and placed in the middle line. 

 According to Gentes, the saccus vasculosus varies considerably in size in 

 different species of teleosts, and may, indeed, be absent altogether, or present 

 only in a rudimentary state. In the cod it is well developed and forms a 

 wide-mouthed sac opening into the infundibulum immediately behind the 

 pituitary recess. It is lined by a single layer of columnar epithelium resting 

 upon a basement membrane. Numerous blood-vessels reach it in the 

 middle line in the interval between the two large lobi inferiores. The 

 columnar cells are large, with a nucleus in each situated near the basement 

 membrane, the part of the cell next the lumen of the sac being clear. The 

 epithelium is thrown into numerous folds which are suggestive of an in- 

 crease of surface for secretory purposes. The arrangement and structure 

 of the saccus vasculosus is such as indicates that it is a gland which secretes 

 into the ventricles of the brain, Gentes believes that it is to be looked 

 upon as a ventral choroid plexus, and that its function is to help in the 

 formation of the cerebro-spinal fluid. It was called an infundibular gland 

 by Rabl-Riickhard (9). The saccus vasculosus of the cod is attached to 

 the brain behind, and its epithelium is continued for a short distance over 

 the ventricular surface. The brain-tissue above it is remarkable for the 

 large ependyma cells which line its internal surface. 



Physiological Action of Extracts of the Lobes of the 

 Pituitary and of the Saccus Vasculosus of the Cod. 



Anterior Lobe. 



Extracts of the anterior lobe proper — chromophil portion of Sterzi and 

 Gentes — have little innnediate physiological effect (fig. 4). The blood- 



