172 



Herrinof 



stated, sought to derive the origin of the blood-vessels of the pituitary from 

 the tissue of the head of the notochord. The exact manner in which the 

 blood-vessels of the anterior lobe of the cat's pituitary are formed is some- 

 what difficult to make out, but in the pig embryo their origin is partly 

 sinusoidal. The cell columns of the anterior lobe grow into large blood- 



Fm. 



-Mesial sagittal section through part of head of 35-mm. kitten. 



remains of cavity of flathke's pouch now recognisable as the epithelial cleft of the pituitary ; 

 b, central cavity of infundibular process ; g, remnant of epithelial duct connecting hypo- 

 physial sac with the nasal mucous membrane ; ;', third ventricle of brain ; k, part of 

 epithelial duct which becomes the tongue - like process of pars intermedia ; I, cells of 

 anterior wall of hypophysial sac (pais intermedia); in, anterior lobe proper; n, vascular 

 knob covered with ependynia cells projecting into cavity of the infundibular process. 



sinuses, pushing the endothelial lining before them. In a pig embryo of 

 60 mm. the appearance of the anterior lobe is very like that of the develop- 

 ing liver. It is not, however, entirely sinusoidal, and some ingrowth of 

 blood-vessels with accompanying connective tissue takes place, the latter 

 being always small in quantity. This method of development of the blood- 

 vessels of the anterior lobe was first pointed out by Gaupp (10) in reptiles. 



