Human Idiot, compared with that of the perfect Brain of Man. 325 



DISSECTION OF THE BRAIN OF A MALE IDIOT. 



The cerebrum was small, and the anterior lobes especially so. The cerebellum 

 projected beyond the posterior lobes of the hemispheres. The convolutions of the 

 cerebrum were small, particularly those of the anterior lobes on the left side, — 

 they were so imperfectly developed, and so closely connected to each other, that 

 they had more the appearance of a tuberculated than of a convoluted surface. 

 The olfactory nerves were small, and very deficient in grey substance, indeed all 

 the coloured parts of the brain were rather pale. The pyramids could scarcely be 

 distinguished, being extremely small, and confounded in the projection of the 

 corpora olivaria ; they did not appear to decussate ; the one on the left side was 

 particularly small. The left hemisphere of the brain was smaller than the one 

 on the right side. The tubercula quadrigemina were of an equal size, and a grey 

 colour on their surface. The pineal gland was large, semi-transparent, and con- 

 tained very little of the gritty matter. On the surface of the left crus of the 

 cerebrum there was a green tinge observed, which, on being cut into, proved to 

 be the locus niger in a disorganized and nearly dissolved state. There were no 

 white strice in the fourth ventricle. The plexus of white filaments at the roots of 

 the olfactory nerves was very plain on the right side, but very imperfect on the 

 left. The brain was tolerably firm. The spinal marrow was hard, and the cere- 

 bellum was soft. The structure, as well as form of the parts in this brain, was 

 imperfect throughout, but most remarkably so on the left side ; the want of agree- 

 ment between the two sides would necessarily impair the functions of the brain. 



The first deviations from the perfect brain of man appear to be with respect 

 to the following parts : — The locus niger, the corpus fimbriatum, the white strice 

 in the floor of the fourth ventricle, the decussation of the pyramids, the distinc- 

 tion of the anterior crura of the fornix, the corpora olivaria, the degree of inter- 

 mixture of the sentient or white filaments in the arbor vitce, the corpora candi- 

 cantia, and the existence of calcareous granules in the pineal gland. 



It is remarkable, that many of these parts are not found in the first stages 

 of foetal life, and some of them not until after birth. The pineal gland, accord- 

 ing to Meckel, is not perfect until the seventh year of infancy. The same parts, 

 also, first decline, and ultimately disappear in animals, according to their scale of 

 organization ; and further, it is chiefly with respect to these parts, that varieties 



