718 NERVOUS SYSTEM. (NERVOUS CENTRES. ABNORMAL ANATOMY.) 



mater and arachnoid immediately near it, 

 tubercular meningitis ; and this may affect more 

 or less of the substance of the brain in its 

 vicinity, causing red softening. 



Cerebral tubercle is seldom or never alone. 

 Other organs of the body are almost invariably 

 affected at the same time, the lymphatic or the 

 mesenteric glands, or the lungs. It is most 

 commonly found in children, and it is not im- 

 probable that it may lie dormant for years until 

 roused to action by some newly-developed 

 morbid excitant. 



Connected with diseased states of the mem- 

 branes of the brain, it should be remarked that 

 in many instances acute affections of the mem- 

 branes of the brain find their point of departure 

 in inflammation of the sinuses. The sinus 

 which is most frequently inflamed is the lateral ; 

 the inflammatory state of this spreads to the 

 neighbouring arachnoid and pia mater, and 

 induces all the consequences of a primary me- 

 ningitis. 



Of the abnormal states of the bruin. The 

 abnormal conditions of the brain may be con- 

 sidered under the heads of 1, congenital, 

 2, acquired or morbid. 



1. Congenital abnormal conditions. A total 

 defect of the brain is found in that state in which 

 the head is wanting ( Aceplialla ) ; and also 

 where there is deficiency of the parietal bones 

 of the cranium, the occipital, temporal, sphe- 

 noid, and frontal being present in an imperfect 

 state, and there being also, in general, spma 

 bifida of the upper cervical vertebrae, there is a 

 deficiency of a considerable portion of the en- 

 cephalon, the medulla oblongata or a portion 

 of it being alone present (Anencephalia). 



The acephalic state is very frequent. It is 

 always associated with complete or nearly com- 

 plete absence of the cranial bones, and frequently 

 more or less of those of the spine. In some 

 the trunk and extremities are perfect, but in 

 very many there are deficiencies to a greater or 

 less degree in the formation of these parts. 



In anencephalia there is a defective state of 

 encephalon, but not an absence of it ; and it 

 seems highly probable that this condition is 

 due, not so much to an original arrest of deve- 

 lopement as to the occurrence of an hydroce- 

 phalic state at an early period of intra-uterine 

 life, the accumulated fluid breaking down the 

 newly formed nervous matter, which wants the 

 support of the cranial bones. 



The extremest degree of this defect is when 

 a large portion of the cranial bones is wanting, 

 and also when there is a large fissure in the 

 spine. In other cases the spinal fissure does 

 not exist. The cranium is largely open on its 

 posterior and superior aspect, the head thrown 

 back, the neck very short and thick, the eye- 

 balls very large and prominent, and the mouth 

 partially open, giving to the features a very 

 hideous expression. 



The hollow of the base of the cranium is, in 

 these cases, filled up by a red, soft, highly vas- 

 cular substance, continuous with the pia mater 

 of the spinal cord. This, in general, appears 

 to be nothing more than the cranial pia mater, 

 which has collapsed into this state by the de- 



struction of the nervous matter, and in which 

 sometimes small masses of nervous matter may 

 be discovered here and there. It is covered by 

 a smooth membrane, which may be an imper- 

 fect arachnoid. In some instances, however, 

 the tumour is of considerable size, more volu- 

 minous, according to Geoffrey St. Jlilaire, than 

 even the normal brain. It is disposed in lobes, 

 which resemble somewhat those of the brain, 

 and which sometimes contain a considerable 

 quantity of serum. 



In less degrees of this condition the cranial 

 bones are more developed, the skull is less 

 open, and the brain and its membranes exhibit 

 a greater degree of perfection. In all the cases 

 water is accumulated in the cerebral cavities. 

 The following case quoted from Penchienati by 

 Breschet in his article Anencephtille, in the 

 Dictionnaire de Medecine, illustrates the ap- 

 pearances in a by no means advanced stage of 

 the deformity. The subject was a girl which 

 had lived three days. The corpora stnata, 

 optic thalami, were present with the hemi- 

 spheres. The lateral and third ventricles were 

 greatly enlarged. The tubercula quadrigemina 

 retaining their vesicular condition were likewise 

 present, and also the pineal gland. These 

 parts presented at the superior part of the cra- 

 nium a red eminence which was uncovered by 

 the skin. 



In some cases where the degree of openness 

 of the cranium is reduced to a fissure, in front 

 or behind, a tumour is found protruding through 

 either fissure, consisting of the brain, imper- 

 fectly developed, inclosed in its membranes. 

 This condition is frequently combined with a 

 greater or less extent of spina bifida. 



The partial deficiencies of the brain itself 

 are infinitely various. Those parts which are 

 most frequently either altogether absent or im- 

 perfectly developed, are those which are not 

 essential to the production of the organic vital 

 phenomena. The commissures are very fre- 

 quently wanting, the smaller ones oftener than 

 the larger, such as the corpus callosum and the 

 pons Varolii. The hemispheres of the bra.n 

 are frequently very imperfectly developed. 

 The medulla oblongata and mesocephale rarely 

 exhibit any material imperfection. 



In all cases of idiotcy there is a manifest 

 imperfection in the developement of the brain. 

 This is sufficiently plain to the most super- 

 ficial observer from the ymall size of the head 

 which is so frequent a character of this state, 

 and which is more especially remarkable in 

 adult life, where the developement of the cra- 

 nium by no means keeps pace with that of the 

 rest of the body. 



As an example of the class of changes which 

 take place in the brains of most idiots, I shall de- 

 scribe the appearances observed in the brain of 

 an adult idiot which I examined in October, 

 1844. 



On the upper surface of the brain the convo- 

 lutions were not developed ; the surface of both 

 hemispheres was perfectly smooth. The fissure 

 of Sylvius was very deep and well marked, 

 extending upwards and backwards; at its pos- 

 terior extremity there was a slight puckering 



