140 WALTER E. DANDY and EMIL GOETSCH 



To secure an injection of the venous supplj^ alone, Prussian 

 blue was injected head wards into the internal jugular vein, there 

 being no valves in the canine jugular to prevent the reversed 

 stream from reaching the intracranial veins and venous sinuses. 

 After the gelatin had been hardened by coohng, a block of tissue 

 containing the hypophysis and its meningeal envelopes intact . 

 was carefully removed, preserved in gh'cerine or creosote, and 

 either studied by the aid of the binocular after clearing, or fixed 

 and sectioned for microscopical study. 



GENERAL CONSIDERATION OF THE CIRCULATION 



The blood supply of the hypophysis is so abundant as to seem, 

 were it actually an unimportant gland, more than commensurate 

 with its functional needs and the possibility of harm from vascular 

 disturbances. 



Situated in the centre of the circle of Willis, it receives the 

 first installments of blood to the brain, its numerous vessels 

 converging from all parts of the circle like spokes to the hub of 

 a wheel, while the venous outflow is equally abundant and the 

 vessels similarly disposed. 



There are three fairly independent circulations to the subdivis- 

 ions of the gland in correspondence with their structural indepen- 

 dence: (1) The supply to the anterior and intermediate lobes; 

 (2) to the posterior lobe; and (3) to a structure which has been 

 discovered during the course of these investigations and which 

 we shall designate the "parahypophysis." 



Vessels of the anterior lobe 



The anterior lobe receives its blood supply from numerous 

 small arteries which converge toward the stalk of the hypophysis 

 (fig. 2.) The great majority of these vessels arise from the anterior 

 half of the circle of Willis. Thus the anterior communicating 

 artery, which is usually small (cf. figure) in the dog, sends off 

 from eight to ten small branches in its course across the optic 

 chiasm; and each posterior communicating artery sends off from 

 three to five more. Furthermore, a pair of vessels on each side 



