THE NERVOUS SYSTEM OF THE DOG 



849^ 



The cerebral hemispheres are very broad behind and diminish in width an- 

 teriorly; 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 extends upward and backward from the sulcus rhinalis a little behind 

 the middle of the lateral surface of the hemisphere. 



2. The ectosylvian fissure has approximately the shape of an inverted 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 Ues above and 

 approximately concentric with the preceding. It 

 also consists of three parts — anterior, middle, 

 and posterior. 



4. The ectomarginal or. collateral fissure 

 runs forward on the dorsal aspect of the hemi- 

 sphere almost parallel with the dorso-medial bor- 

 der. A little in front of the middle of the surface 

 it gives off a short ansate fissure (F. ansata) 

 which runs obliquely medially and forward. It 

 is usually continued anteriorly by the coronal 

 fissure, and may be in continuity posteriorly 

 with the medilateral (or post-lateral) fissure. 



Longitudinal fissure 



Olfactory bulb 

 Frontal yole 



Fig. 679. — Brain Stem of Dog; Doksal Vibw. 



a, Spinal cord; I, dorsal median groove; c, c', funicu- 

 lus gracilis; c", clava; d, d' , funiculus cuneatua; d" , tuber- 

 culum cuneatum; e, funiculus lateralis; e', tuberculum cin- 

 ereum; /, medulla oblongata; Z, II, III, foveas of floor of 

 fourth ventricle (fossa rhomboidea); g, limiting groove; h, 

 median fissure; i, eminentia medialis; h, ala cinera; I, I'. 

 pons; m, posterior peduncle, and n. middle peduncle, of cere- 

 bellum (cut); o, anterior peduncle of cerebellum; p, v', cor- 

 pora quadrigemina, anterior and posterior; q, q', peduncles 

 (brachia) of corpora quadrigemina; r, thalamus; s, massa 

 intermedia;- t, stria meduUaris; u, anterior tubercle of 

 thalamus; c, pulvinar; w, corpus geniculatum laterale; x, 

 corpus geniculatum mediale. (After EUenberger, in Leiser- 

 ing's Atlas.) 



Cerebellum 



Medulla 

 1 oblongata 



Fig. 680. — Brain of Dog; Dorsal View. 

 Fissures: 1, Lateral; 2, ectosylvian; 3, suprasyl- 

 vian; 4, ectomarginal (or collateral); 4', ansate; 5, 

 coronal; 6, eotolateral; 7, entomarginal; 8, presylvian 

 (or orbital); 9, cruciate; 10, medilateral (separated 

 from entomarginal on right side, but connected with it 

 on left hemisphere) ; il, f. proreaj. 



5. The coronal fissure is usually the 

 continuation of the ectomarginal. It runs 

 forward and downward, curving around the 

 cruciate fissure, and ends behind the middle 

 of the presylvian fissure. 



6. The eotolateral fissure hes between 

 the posterior part of the ectomarginal fissure 

 and the suprasylvian fissure. 



7 The entomarginal fissure Kes between the anterior part of the ectomarginal fissure and 

 the dnrso-medial border. It is often indistinct and not rarely absent. , ,, , ,. ,. 



thedorsomemalDom ^_^^^^^^^^ t^.^ed the orbital-begms at the sulcus rhinahs, 



a Uttle in front of its middle, and curves over the anterior third of the lateral surface of the hemi- 

 sphere in front of the coronal fissure. 

 64 



