38 Journal of Comparative Neurology. 



young animal of which we are treating. Such a difference of 

 development obtains in the case of the adult human pineal as 

 compared with that of the child. Since the chimpanzee pineal 

 by reason of the relatively greater development of an unpaired 

 hollow stalk leading to the pineal body, approaches nearer the 

 original form, it is justifiable to say that the latter shows a less 

 rudimentary character than the pineal of man, provided of course, 

 we here have to treat with constant relations. Whether such 

 be the case, with the present meager observations cannot be 

 stated with certainty. 



A third pineal of a chimpanzee presented some peculi- 

 arities and digressions from the relations just described, so that 

 they need a special investigation. There is such a reduction of 

 this organ that it is practically absent. There is neither a trace 

 of the pineal body nor of the unpaired stalk. The two ped- 

 uncles appear as two small projections with their tips directed 

 backwards, which, similar in size, are situated on each 

 side of the posterior edges of the trigonum habenulae, and are 

 united to each other by a narrow commissure. The latter forms 

 the posterior projection of the taeniae medullares which Wends 

 here. The trigona habenulae moreover, in comparison with 

 the first described cases, are very slightly developed since 

 they are much less strongly arched and are not so sharply sep- 

 arated from the neighboring region of the optic thalamus. An 

 explanation of this can be sought for in the defective develop- 

 ment of the epiphysis itself, particularly in the stalk and pedun- 

 cle, inasmuch as the nerve fibres of the latter, running over 

 the ganglion of the trigonum habenulae to the taenia medullares, 

 are here obviously reduced. The discussion then cannot con- 

 cern the pineal recess, but on the contrary a very significant de- 

 velopment of the recessus supra-pinealis which extends as a 

 pouch-like evagination of the tela choroidea posteriorly to the 

 middle of the anterior corpora quadrigemina. Here accord- 

 ingly, not only its upper but also its lower wall will be formed 

 of the tela choroidea, and not as in the other case from the 

 upper surface of the pineal. Finally, Moller states that he 

 found the pineal entirely absent in a human brain and adds that 



