326 THE PINEAL ORGAN 



the special characters of an actively functioning endocrine gland. The 

 basal portion of the stalk or epiphysis in the frog, as was described in 

 Chap. 19, p. 228, Figs. 161 and 166, undergoes a certain degree of 

 development and differentiation ; in the rat, however, this segment 

 remains small and insignificant. It may be noted here that most of the 



Fig. 227. — Pineal Organ and Habenula of a Sheep's Brain seen from above. 



(After J. Wilkie.) 



A. Col. : anterior colliculus. Pin. : pineal organ. 



CN. iv. : fourth cranial nerve. Pulv. : pulvinar. 



Hab. : habenula. Str. Th : stria thalami. 



Par. T.B. : paraterminal body. Taen.Th. : taenia thalami. 

 P. Col. : posterior colliculus. 



experimental work that has been carried out on rats has been by way of 

 the injection of extracts of the epiphysis of the horse, or ox, or grafts 

 of the epiphysis ; Kolmer and Lowy have, however, cauterized the pineal 

 region in young rats, and Lehmann removed the gland in rats and mice 

 without any positive results. 



