264 



THE CAT. 



[CHAP. ix. 



IP. 



mm 



conical process, the infimdibukim. At the end of the infundibulum 

 is a small oval reddish mass called the pituitary body, which is 



received into the pituitary fossa 

 (or sella turcica) of the sphenoid 

 bone. 



Between the diverging crura 

 and the corpus albicans, is a 

 depressed surface of greyish 

 matter perforated by numerous 

 small vascular openings, whence 

 it is termed the locus perforatus 

 posterior. 



The tuber cinereum is a 

 lamina of grey nervous matter 

 extending forwards from the 

 corpus albicans to the median 

 junction of the optic tracts, or 

 optic commissure. 



The pituitary body is very 

 vascular, and in structure is 

 like a ductless gland, consisting 

 as it does of connective tissue 

 with granular matter and nu- 

 cleated cells. 



Another grey space with 

 vascular openings called the 

 locus perforatus anterior is 

 placed on each side just in 

 front of each optic tract. 



Anterior to and beside these 

 small median parts are those 

 voluminous masses the cerebral 

 hemispheres, which thus form 

 a very large part of even the 

 under surface of the brain. 



The great longitudinal fissure 

 is seen in the middle line in 

 front, and another but small 

 (Fig. 125) lateral fissure (called 

 the Sylvian fissure) separates 



the anterior (or frontal) lobe from the one behind (or temporal 

 lobe) of the same hemisphere. The temporal lobes form two 

 great prominences on each side of the brain's under surface. 

 Each is bounded behind by the cerebellum, and is well marked 

 off in front by the Sylvian fissure. 



In a groove on the under surface of each frontal lobe is a body, 

 shaped something like a life-preserver, with an oblong head and a 

 thick stalk. This is the olfactory lobe or bulb. It is made up 

 largely of grey matter, but also contains white fibres. The stalks 



Fig. 128. BASE OF THE BRAIN. 



F. Frontal lobe. 

 T. Temporal lobe. 

 ol. Olfactory lobe. 

 m. Medulla oblongata. 



cb. Cerebellum. 



p. Pituitary body. 

 pv. Pons Varolii. 



cc. Crura cerebri. 

 s. Sylvian fissure. 



mm. Corpora mammillaria or corpiis albicans. 

 Ip. Locus perforatus anterior. 

 ct. Corpus trapezoideum. 

 pa. Anterior pyramid. 



I. Source of olfactory nerves. 



II. Optic nerve. 



///, IV, VI. 3rd, 4th, and 6th nerves (those of 



eye-muscles). 

 V. Trigeminal nerve. 



VII. Facial nerve. 



VIII. Auditory nerve. 



IX. Glosso-pharyngeal. 



X. Pneumogastric. 

 XL Spinal accessory. 

 XII. Hypo-glossal. 



