726 



THE NERVOUS SYSTExM OF THE DOG 



In the deep interpeduncular fossa are two small Isands which indicate the course of 

 the fasciculi retroflexi, tracts which connect the habenular and interpeduncular 



ganglia. The mammillary body is double. The 

 tuber cinereum is relatively large. The pituitary 

 body is circular and rather small. 



The cerebral hemispheres are very broad 

 behind and diminish in witlth anteriorly; there is 

 a sudden narrowing at the frontal poles, which 

 are flattened laterally. The tentorial surfaces 

 are concave and form a deep cavity which re- 

 ceives the anterior part of the cerebellum. The 

 arrangement of the fissures and gyri is simpler 

 than in the animals previously examined. The 

 chief fissures are as follows: 



1 . The lateral fissure (of Sylvius) extends up- 

 ward and backward from the sulcus rhinalis a little 

 behind the middle of the lateral surface of the hemi- 

 sphere. 



2. The ectosylvian fissure has approximately 

 the shape of an invert(>d u, and curves over the 

 lateral fissure. It is regarded as consisting of three 

 parts — anterior, middle, and posterior (F. ectosylvia 

 anterior, media, posterior). 



3. The suprasylvian fissure lies al)ove and ap- 

 proximately concentric with the preceding. It also 

 consists of three parts — anterior, middle, and pos- 

 terior. 



4. The ectomarginal or collateral fissure runs 

 forward on the dorsal aspect of the hemisphere 



almost parallel with the dorso-medial border. A little in front of the middle of 

 the surface it gives off a short ansate fissure (F. ansata) which runs obliquely 

 inward and forward, and is continued by the coronal f ssure. 



Fig. 642, — Cerebrum of Dog, Dorsal 

 View. 

 a, End of lateral fissure (of Syl- 

 vius); b, ectosylvian fissure; c, c' , c", 

 suprasylvian fissure; d, fissura ansata 

 minor; e, ectolateral fissure; /, ectomar- 

 ginal or collateral fissure; g, fissura an- 

 sata; h, coronal fissure; i, medilateral 

 fissure; A-, entomarginal fissure; /, post- 

 cruciate fissure; m, cruciate fissure; o, 

 presylvian fissure; p, fissura prorea. 

 (After Ellenberger, in Leisering's Atlas.) 



Fig, 543. — Fissures of L^tkr-^l Surface of Cere- 

 brum OF Dog, Right Side, 

 a, Fissura prorea; fc, frontal fissure; c, ol- 

 factory fissure; d, d\ sulcus rhinalis; e, presylvian 

 fissure; /. precruciate fissure; g, postcruciate fissure; 

 h, cruciate fissure; i, lateral fissure (of Sylvius); 

 /,-, k' , k'\ suprasylvian fissure; /, I', /", ectosylvian 

 fissure; w, fi.ssura ansata minoi ; n, ectomarginal or 

 collateral fissure; o, fissura ansata; p, coronal fissure; 

 (/, ectolateral fissure; ', medilateral fissure; s, 

 entomarginal fissure. (After Ellenberger, in Leiser- 

 ing's Atlas.) 



Jv A 



Fig. 544. — Right CivRkbhal IIeiiisphere of Dog, 

 Inner Side. 

 1, Corpus callosum; 1' , genu, 1" , splenium of 

 cori)us callosum; «, genual fissure; /), splenial fissure; 

 f, .sujjrasplenial fissure; rf, hippocampal fissure; e, 

 sulcus corpori.s callosi; /, postsplenial fissure; g, lesser 

 cruciate fissure; /(, cruciate fissure. (After Ellen- 

 berger, in Leisering's Atlas.) 



5. The coronal fissure is the continuation of the ectomarginal. It runs forward 

 and downward, curving around the cruciat(> fissure, and ends behind the middle 

 of the presj'lvian fissure. 



