2. Morbid conditions of the brain.—Hy pertrophy. — The examples of hypertrophy of the brain which are on record are not numerous, and it is difficult to attribute the appearances, which are said to indicate this condition, to a mere increase in the nutrition of the organ. Adopting the terni, however, in deference to the high authorities who have ap plied it, it may be stated that the anatomical characters of a hypertrophic brain are as fol lows :— The brain appears too large for the skull; on the removal of the calvaria the dura mater seems perfectly tense and filled by the brain ; it appears thinner and more transparent than is quite normal, and there is no trace of fluid in the subarachnoid space.
The hemispheres are large, and their convo lutions lie closely packed beside each other, and flattened. The ventricles of the brain are small, exhibiting the same condition as the fissures between the convolutions. The surface of the arachnoid as well as of the intra-ventri cular eminences is dry or nearly so.
The substance of the brain is universally firm, and cuts somewhat like cartilage ; it is exsangueous, the principal accumulation of blood being in the pia mater. The colour of the grey matter becomes so changed as to be scarcely different from the white.
It is as yet uncertain what is the precise change which the brain undergoes in this con dition. We know that there is an increase of substance, but whether that be an increase in the normal size of the fibres and vesicles of the two varieties of nervous matter which are found in the brain, or in their number, or whether it be a deposition of new material, with or with out increase in the size or number of the ele mentary parts of the organ, has yet to be deter mined by microscopical examination.
It is most probable that the disease consists not merely in an increased, but also in a per verted nutrition, and that new material is depo sited between or in the proper anatomical ele ments of the brain.
In some instances there is, along with the signs of increased nutrition in the brain,evidence of a similar condition of the cranial walls. The bones of the skull are, in such cases, much thicker than usual. In others, however, the bones seem to yield under the pressure from within, and they become thin, and more or less transparent in parts.
There appear to be two classes of cases in which an hypertrophic state of brain occurs. In
one class the functions are carried on well, and the only sign of the morbid change is derived from the undue enlargement of the head, which becomes almost too large for the body, and too heavy for the muscles of the neck to support conveniently ; in the other there may or may not be enlargement of the head, but there are marks of cerebral disturbance in more or less dullness of intellect, and in the frequent re currence of epileptic fits.
Dr. Watson has placed upon record two in stances of this enlargement of the brain's sub stance which are highly interesting and will serve to illustrate the varieties above alluded to.
One case was that of a young woman wt. 19. Her countenance was sallow, lips pale. She complained of pain in her chest and limbs, of great and increasing debility and wasting, and of nightly perspimtions, and she was subject to attacks of epilepsy. She died in a prolonged epi leptic paroxysm. The following appearances were observed at the post-mortem examination.
" When the surface of the brain was exposed by the removal of the skull-cap and dura meter, it was observed that the convolutions were re markably' flattened, so that the little furrows be tween them were nearly effaced, and the sur face of the arachnoid membrane was perfectly dry. These are not very unusual, although they are unnatural appearances. I had often seen such before ; and I ventured to say we should find some cause of strong pressure in the central part of the brain, effusion of serum into the ventricles, or a large extravasation of blood. But to my great surprise, and much to the discredit of my prophecy, we found nothing of the kind. The ventricles were even smaller than natural, and contained scarcely any moisture. The skull-cap was afterwards exa mined, and the bone was found to be uncom monly thick, dense, and heavy ; and its inner surface without being rough was very irregular." The state of the bloodvessels of the brain was not noticed. It is to be regretted likewise that the weight of the brain has not been stated, for it is obvious that a gradual and pretty uniform diminution of the cranial cavity by the thick ening of the bone might have produced the flat tening and condensation of the brain described.