DISSECTION OF THE DOG 



213 



s. auprasylvius "- - _ ^ 



*. ectosylvius . 



^'S. orbUalis 



s. cruciatus 

 s. coronalis 



s. lateralis 



little moment — ectolateral and post-lateral — indent the surface of the hemisphere 

 in the neighbourhood of the occipital pole. Consequent upon the lateral 

 inclination of the coronal sulcus, an area of cerebral cortex, roughly quadri- 

 lateral in form, is isolated. In this area is the cruciate sulcus (s. cruciatus) 

 which crosses the border of the hemisphere and is continued onto its medial 

 surface. In the oral part of the lateral surface is the long, curved orbital 

 sulcus (s. orbitalis), one end of which lies close to the cruciate sulcus, while 

 the other joins the rhinal fissure. 



Medial surface.— 'The cruciate / ^__ Bldbm afactorius 



sulcus is prolonged, as has been 

 said, to the medial surface of 

 the hemisphere, where it is very 

 generally continuous with the 

 intercalary sulcus (s. intercalaris), 

 so named because of its inter- 

 position between the cruciate 

 sulcus on the one hand and the 

 calcarine sulcus on the other. 



The calcarine sulcus (sulcus 

 calcarinus), one of the most im- 

 portant of the cerebral grooves, 

 forms an angle with the inter- 

 calary sulcus with which it is 

 continuous, and is confined to 

 that part of the medial surface in 

 contact with the tentorium of the 

 cerebellum. Between the margin 

 of the hemisphere and the inter- 

 calary and calcarine sulci are one 

 or two secondary grooves of no 

 great depth and inconstant in 

 disposition. The medial surface 

 of the hemisphere oral to the 

 cruciate sulcus is also indented by a number of grooves of no great moment. 



A fissure of fundamental importance — the hippocampal fissure (fissura 

 hippocampi) — forms the medial boundary of the pyriform lobe. 



Dissection. — Part of one cerebral hemisphere should be removed to a 

 level with the corpus callosum. This must be done by making a suc- 

 cession of slices in planes parallel to that of the corpus. The specimen 

 in which the two hemispheres have been separated by a longitudinal 

 incision, is of service in acting as a guide to the direction and depth to 

 which the slices should be removed. As soon as the corpus callosum can 

 be plainly seen, it is well to remove the remains of the convolution 



s. postsylvius . 



i s. postlateralis 



s. eclolateralis 



Fig. 66. — Dorsal view of the cerebral hemisphere. 



