474 ANATOMICAL TECHNOLOGY. 



1195. Callosum (az.\ cl.Fig. 88, 104, 115, 117, 122, 125; PI. II, Fig 4; PI. Ill, 

 Fig-. 13 ; PI. IV, Fig. 15-17, 20. Gray, A, 623; Quain, A, II, 537. 



Syn, Corpus callosum, commissura magna, trabs cerebri. 



A broad band of nerve fibers connecting the mesal surfaces of the hemispheres along a 

 line dorsad of the fornix and curved ventrad at each end. The cephalic curvature is the 

 genu and the caudal the splenium. 



In nearly its caudal half, the callosum is in contact with the fornix at the meson and 

 for 1-2 mm. laterad (Fig. 122, 1149). With care the callosum may be dissected up from 

 the fornix, and at the splenium the two are then seen to be continuous. In fact, a simple 

 way of describing their relations is the following : 



The two hemispheres, originally separate, become united along two lines represented 

 by the callosum and the fornix. The former is approximately straight, excepting at its 

 ends, the cephalic corresponding with the genu and rostrum. The latter forms the seg- 

 ment of a circle, but the caudal end turns dorsad to become continuous with the caudal 

 end of the callosal line which is curved ventrad at the splenium. 



The fibers constituting the larger part of the callosum pass dorsad of the proc&lia and 

 thus constitute its roof ; the fibers of the fornix pass ventrad of the proccelia and thus 

 enter into the composition of its floor ; the fibers of the splenium are intermediate, and are 

 partly continued into the hypocampa and partly into the general caudal part of the hemi- 

 sphere. These relations are indicated in PI. IV, Fig. 19, 20. 



Notwithstanding the fact that the callosum exists only in mammals, is larger, as a 

 rule, in the higher members of the group, and presumptively has great physiological 

 importance, there are recorded several cases of its more or less complete absence from man, 

 once without serious lack of mental or physical power (Malinverni [Henry, 7]) ; and the 

 senior author has reported (13) a case of its complete absence in a cat which is not 

 known to have been peculiar during life. 



1196. Canalis centralis (myelonis), (az.\ Cn. ce. Fig. 99, 100, 109, 113, 117; PI. II, 

 Fig. 4. Gray, A, 68 ; Quain, A, II; 500. 



The central canal of the " cord." 



The mesal canal of the myelon, which expands cephalad and is opened up into the dor- 

 simesal fissure so as to form the metacodia. In the cat this canal persists through life, but 

 in man it is said to be commonly obliterated in the adult, excepting at the cephalic end. 



1197. Carina (ctz), en. This is a mesal ridge upon the vent ro caudal aspect of the 

 fornix, extending from the crista the entire length of the delta. It varies in distinctness 

 and does not appear upon any of the preparations here figured, but is very well marked 

 in Prep. 530, M. C. U. 



1193. Cauda striati, cd. s. This is not distinctly shown in the figures and has not 

 been accurately observed by us. 



The sbnder tail-like prolongation of the striatum. 



Former writers who mentioned this portion of the striatum (Todd, Gratiolet, Hirsch- 

 feld, and ("uvier, B, III, 51) gave it no special name. Recently it has been described by 

 Dalton (1, 12) under the name of surcingle. Having vainly requested him to substitute 

 for this vernacular term some equivalent technical one, the senior author reluctantly pro- 

 posed (9, 134) the name here employed, which is approved by Spitzka, 7, 165. 



1199. Cella media, eel. m.P\. IV, Fig. 15 ; 1147. Gray, A, 625 ; Quain, A, 

 II, 540. 



The central or intermediate portion of the procodia ; its limits are not defined. 



1200. Cerebellum (az.\ cbl. Fig. 88, 104, 113-117; PI. I, Fig. 1, 2; PI. II, Fig. 

 3, 4 ; PI. IV, Fig. 15 ; 1074 (C). Gray, A, 632 ; Quain, A, II, 515. 



Syn. Cerebrum parvum. 



