362 DISSECTION OE THE RABBIT 



iv. The pineal body is connected by a tubular stalk 

 with the hinder end of the velum interpo- 

 situm. 



Bemove the velum interpositum, so as to open the third 

 ventricle. 



V. The third ventricle, or cavity of the fore-brain, 

 is a median vertical cleft between the optic 

 thalami. It is very narrow from side to side, 

 and communicates through the foramina of 

 Monro with the lateral ventricles. 



Fig. 63. — Lepus cuniculus. Transverse section of the brain, passing 

 through the middle commissure of the third ventricle. The shading 

 indicates diagrammatically the distribution of white and grey matter. 

 The section is taken somewhat obliquely, so as to show different parts 

 on the two sides, (a. m. m.) 



A, optic thalamus, forming the side-wall of the third ventricle. B, part of 

 the third ventricle above the middle commissure. C, middle commissure. D, 

 infundibulum. E, corpus callosum. T", temporal lohe of the left cerebral hemi- 

 sphere. Q-, descending comu of the right lateral ventricle. H, hippocampus 

 major. 



e. The mid-brain, or mesencephalon. 



i. The corpora qnadrigemina, or optic lobes, form 

 the dorsal portion of the mid-brain, and are 

 now well seen. 



