THE BRAIN IN THE EDENl'ATA. 



295 



the clearly defined rliiual fissure in Tamandua, tlie non-delineation of a corresponding 

 fissvire in his figure of Cycloturus cannot he regarded as any indication of its absence. 



The illustrations which the earlier observers (Tiederaann, Leuret, and Rapp) have given 

 of the brain in the Sloths convey practically no information concerning those regions of the 

 brain which we have just been considering in the Aard-vark and Ant-eaters, and the figm-es 

 which Pouchet [op. cit.) has given of the Brady podiclce do not represent even a feature so 

 fundamental as the rhinal fissure. Professor Turner's representation * of the brain of 

 Choloepns Hoffmanni, so far as I am aware, is the only figure wiiich represents this feature 



Fig. 10. 



psalterium dors. 



psalterium ventr. / 

 '^corp. callos. / 



euJc. Umitans pallii 



bulb, olfact. 



fimbria 



hjppocamp. inversus 

 fascia dentata 

 -fiss. hippocampi 



fisB. rhinal. 



ped. olfact. -' ; 



taberoul. olfact. i 

 area praeoommiss. > 



\ tract, opt. 



lob. pyriform. 



i_ tuber, tr^ot. olfact. 

 .commiss. ant. 



lamiua terminalis 

 Mesial surface of right central licmisphere of Tamancliut. Enlarged 2. diam. 



in the brain of the Sloths. Of the two brains of Bradypus tridactylus at my disposal, 

 one had almost reached the adult state, whereas the other was much younger, since it was 

 taken from an animal measuring only 34 cm. from the nose to the anus. In the former 

 the anterior rhinal fissure begins in the ordinary manner and extends obliquely upward 

 and backward, and when it reaches a point midway between the anterior and posterior 

 poles of the hemisphere it joins the posterior rhinal fissure alino.st at a right angle (fig. 11). 



The posterior rhinal fissure forms an arc, the postei"ior extremity of which crosses the 

 posterior border of the hemisphere at about the same horizontal level as the cephalic 

 extremity of the anterior rhinal fissure. 



In the younger brain the two parts of the rhinal fissure approximate much more 

 closely to the horizontal, so that their angle of junction is very obtuse. The posterior 

 rhinal fissure is represented merely by a very shallow furrow. 



In Cholcepus didactylus and, jvidging from Turner's figure [op. cit.), also Choloepiis 

 Hoffmanni, the angle of meeting of the two parts of the rhinal fissure is quite as obtuse 



* AV. Turner, op. cit., Journal of Anatomy and Physiologj-, vol, xxv. 



41* 



