MAY, 1921. BRAIN OF C^ENOLESTES HERRICK 157 



THE BRAIN OF C&NOLESTES OBSCURUS. 

 BY C. JUDSON HERRICK. 



Plates XXI-XXII. 



These notes are based on a single female specimen which had been 

 preserved in formalin and later transferred to alcohol. Since the cranial 

 cavity had not been opened before the specimen was put into the harden- 

 ing fluid, the preservation of the brain is not as perfect as might be 

 desired. In particular, the swelling of the brain tissue produced by the 

 formalin has caused considerable compression of the brain within the 

 endocranial cavity, thus possibly exaggerating somewhat the superficial 

 relief, so far as this conforms to the sculpturing of the endocranial cavity, 

 and obscuring some other features. 



The brain was very skillfully removed from the skull of the alcoholic 

 specimen in the Anatomical Laboratory of the University of Chicago 

 by Dr. G. W. Bartlemez and drawn under the Zeiss stereo-binocular 

 microscope by Mr. A. B. Streedain. Since it seemed desirable to pre- 

 serve the brain intact in the hope of a later opportunity to prepare it 

 for microscopic examination, this report must of necessity be limited 

 to the superficial anatomy. 



Measurements. The dimensions as measured on the alcoholic 

 specimen' are as follows: 



Total length, tip of olfactory bulb to first spinal nerve . 14. 1 mm. 



Length, tip of olfactory bulb to rostral end of cerebral hem- 

 isphere 2.6 mm. 



Length of cerebral hemisphere 10.0 mm. 



Length of cerebellum on longitudinal axis of brain in me- 

 dian plane 3.0 mm. 



Greatest width of both olfactory bulbs 7.6 mm. 



Greatest width of both cerebral hemispheres . . . . 1 1 . 8 mm. 



Total width of cerebellum and flocculi 1 1 . o mm. 



Width of cerebellum exclusive of flocculi 8.8 mm. 



For our most precise knowledge of the brains of lower mammals 

 we are indebted to the researches of Elliot Smith. Throughout this 

 account we shall make frequent references to his papers and base our 

 interpretations to a large extent upon them. His papers cited in the 

 appended bibliography give references to the other relevant literature. 



The general form of the brain of this little marsupial is evident from 

 the figures. It is apparent that we have here before us one of the 

 simplest types of mammalian brain hitherto described. The brain is 

 strongly macrosmatic, as shown by the enormous size of the olfactory 

 bulbs and secondary olfactory area. 



