INTERNAL PARTS 551 



matter, viz., phosphate and carbonate of lime, with a little phosphate 

 of magnesia and ammonia (Stromeyer). It is found at all ages, fi'e- 

 quently in young children, and sometimes even in the foetus. It 

 cannot, therefore, be regarded as the product of disease. 



Beneath the peduncle of the pineal gland, is a collection of grey 

 matter distinct from the rest of the thalamus and called the ganglion of 

 the peduncle of the pineal gland (ganglion of the habenula). Fibres 

 arise from it and pnss down to the crus. 



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 coi"pora amylacea occiu- 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 propor- 

 tionally larger than in the human subject, and less loaded with the matter of 

 acervulus cerebri. 



^^Tiether the pineal gland consists of nerve-tis5ue is still uncertain, lileynert 

 regards it as one of the centres for the fibres of the crus, but Henle and others 

 consider that it resembles most the supra-renal capsules. 



The corpora or tiiTberciila quadrigeniina are four roundea emi- 

 nences, separated by a crucial depression, and placed two on each side 

 of the middle line, one pair before the other. 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 {nates) are somewliat larger and 

 darker in colour than the posterior (testes). In the adult, both pairs 

 are solid, and are composed of white substance on the surface, and 

 of grey matter within. (See p. 5G3.) 



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

 are derived from the fillet (see p. 55 G). 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 cerehello ad cerebrum, or superior peduncles of the cerebellum. 

 At each side of the corpora quadrigemina there proceed outw^ards two 

 white bands, prominent on the surface and sometimes named anterior 

 and posterior hrachia. The fibres of the anterior pass to the thalamus 

 opticus, the inner corpus geniculatum, and the optic tract ; those of the 

 posterior to the inner corpus geniculatum and the crus cerebri. Ac- 

 cording to Meynert, many of their fibres pass directly to the cortical 

 substance of the hemisphere. 



In the human brain the quadi-igeminal bodies are small in comparison with 

 those of animals. In ruminant, soliped, and rodent animals, the anterior tuber- 

 cles are much larger than the posterior, as may be seen in the sheep, horse, and 

 rabbit ; and hence the name nutcs, formerly apphed to the anterior, and testes to 

 che posterior tubercles. In the brains of carnivora, the posterior tubercles are 

 rather the larger. In the foetus of man and mammals these eminences are at fii'st 

 single on each side, and have an internal cavity communicating with the ventri- 

 cles. They are constant in the brains of all vertebrate animals ; but in fishes, 

 reptiles, and bu-ds, in which animals they receive the name of optic lobes, they 

 are only two in number, and hollow : in marsupialia and monotremata, they are 

 also two in number, but are solid. 



Optic tracts and corpora geniculata. — The optic tracts, which 

 have already been referred to in connection with the base of the cere- 



