178 Herring 



from that of the anterior lobe, and it is because of the occurrence of colloid 

 vesicles in this situation that the mammalian posterior lobe has been 

 termed by K oil ike r (17) an infundibular gland. Whether the epithelium 

 of the pars intermedia of the mammalian pituitary has a similar function 

 to that of the saccus vasculosus of fishes is a difficult question to answer. 

 Extracts of the saccus vasculosus of the cod do not appear to have the same 

 physiological action as extracts of the posterior lobe of the mannnalian 

 pituitary when injected into the blood ; but ni}' investigations into the 

 comparative phj^siolog}" of the vertebrate pituitary are not sufficiently 

 advanced to make any conclusive statement on this point. The presence of 

 epithelial cells of the pars intermedia in the interior of the cavity of the 

 posterior lobe of the cat's pituitary renders it probable that they furnish 

 some material which passes in the direction of the brain. There must be 

 some significance in the fact that in all craniate vertebrates the cerebro- 

 spinal canal has in close proximitj' to its anterior end, and intimatelj' bound 

 up with it, a glandular organ connected with the mouth. In the Ascidian 

 larva a subneural gland or hypophj'-sis cerebri occupies the same position. 

 Andriezen (1) described in the Ammocoete and larval Amphioxus a sub- 

 neural gland, a duct lined with ciliated epithelium affording a communica- 

 tion between the buccal and the neural cavities, and a group of nerve cells 

 around and at the back of the upper opening where the duct widens into 

 the ventricular cavity ; an arrangement, in fact, which is veiy similar to 

 that found in the larval Ascidian. Andriezen believed that the buccal 

 ventricular duct serves as an inlet for oxygenated water to the .spinal cord, 

 the nerve cells acting as a sensory mechanism to test the quality of the 

 water admitted. In higher animals the water vascular duct disappeai's 

 and the posterior lobe gradually loses its nerve substance. The anterior 

 lobe or subneural gland alone remains functional, but its secretion is carried 

 to the brain by lymphatics and blood-vessels. Sensory structures have 

 been described in the infundibular region by Boeke (6) and by Gemelli 

 (11) in fishes. There are, as already stated, no appearances indicative of 

 such in the posterior lobe of mammals. Andriezen's view is to some 

 extent similar to the one expressed by Kupf fer, but his anatomical data 

 do not agree with the description of the larval Amphioxus as worked out 

 by Willey and other authorities. 



If the anterior lobe of the pituitary body is to be regarded as the 

 remnant of an old mouth into the neural canal, it is possible that such a 

 connection will occasionally show itself in the course of development. In 

 one cat embryo I have met with a communication between the epithelial 

 cleft and the central ca%'ity of the posterior lobe. The opening between the 

 two is at the postero-superior extremity of the posterior lobe, and it has 

 been rendered possible by the spreading of Rathke's sac further backwards 

 than usual. The cleft or remnant of the original lumen of the buccal 

 invagination is in open continuity through the infundibulum with the 

 cavity of the third ventricle. The opening is a median one, and 



