552 THE CEREBRUM. 



The pineal body or gland (conarium) is a small reddish body, which is 

 placed beneath the back part of the corpus callosum, and rests upon the 

 anterior elevations of the corpora quadrigemina. It is attached to the under 

 surface of the velum interpositum, so that it is liable to be torn away from 

 the brain in removing that membrane. It is about the size of a small 

 cherry-stone. Its base of attachment, which is its broader part, is directed 

 forwards, and is connected with the rest of the cerebrum by white substance. 

 This white substance is principally collected into two small rounded 

 bundles, named peduncles of the pineal gland, which pass forwards upon 

 the optic thalami along their upper and inner borders, and may be 

 traced as far as the anterior pillars of the fornix, in conjunction with which 

 they descend. These peduncles are connected with each other behind, and 

 the band of union between them is adherent to the back of the posterior 

 commissure. 



This band is represented by Reichert as folding forwards and then backwards, so 

 as to leave a hollow, which he calls recessus pinealis, opening backwards above the 

 pineal body. Some anatomists have described two inferior peduncles, which descend 

 upon the inner surface of the thalami. 



The pineal gland is very vascular. It is hollowed out into two or more 

 cells, which, sometimes at least, open anteriorly into the ventricle, and 

 almost always contain, besides a viscid fluid, a quantity of gritty matter, 

 named acervulus cerebri. This consists of microscopic round particles, 

 aggregated into small compound masses, which are again collected into 

 larger groups. It is composed of the so-called amylaceous or amyloid 

 bodies, and of earthy salts combined with animal matter, viz., phosphate 

 and carbonate of lime, with a little phosphate of magnesia and ammonia 

 (Stromeyer). It is found at all ages, frequently in young children, and 

 sometimes even in the foetus. It cannot, therefore, be regarded as the 

 product of disease. 



This sabulous matter is frequently found on the outside of the pineal body, or 

 even deposited upon its peduncles. It is found also in the choroid plexuses ; and 

 scattered corpora amylacea occur in other parts of the membranes of the brain. 

 Huschke has pointed out that the pineal body is larger in the child and the female 

 than in the adult male. In the brains of other mammals it is proportionally larger 

 than in the human subject, and less loaded with the matter of acervulus cerebri. 



The corpora or tubercular quadrigemina are four rounded eminences, 

 separated by a crucial depression, and placed two on each side of the middle 

 line, one before another. They are connected with the back of the optic 

 thalami, and with the cerebral peduncles at either side ; and they are 

 placed above the passage leading from the third to the fourth ventricle. 



The upper or anterior tubercles are somewhat larger and darker in colour 

 than the posterior. In the adult, both pairs are solid, and are composed of 

 white substance on the surface, and of grey matter within. 



They receive bands of white fibres from below, the majority of which are 

 derived from a fasciculus named the fillet. A white cord also passes up 

 on each side from the cerebellum to the corpora quadrigemina, and is 

 continued onwards to the thalami : these two white cords are the pro- 

 cessus a cerebello ad cerebrum, or superior peduncles of the cerebellum. At 

 each side of the corpora quadragemina there proceed outwards two white 

 bands, which pass to the thalami and to the commencements of the optic 

 tracts. These bands are prominent on the surface, and are sometimes named 

 brachia. 



