The brain itself is seldom or never in a healthy condition; the morbid changes to be distinguished in it differ greatly in degree in different cases, but still, in almost every case, some morbid change is to be discerned. These changes consist of an altered state of its substance, or of its cavities, or of both. The most usual change apparent in its substance is a higher degree of vascularity than natural. This increased vascularity is sometimes confined to the surface; sometimes it is more manifest deep in its substance; and, while common to both, it may exhibit different degrees of intensity in either. When on the surface, this preternatural vascularity is denoted by a greater fullness of the vessels, and, apparently by an increase in their number; when within the substance, by a greater number of bloody points, which are rendered visible by an incision with the scalpel. And in both situations it may exist in all degrees, from a faint blush to a deep and vivid redness. The substance itself is sometimes softer, sometimes firmer than natural. The softening differs in degree and in extent. Sometimes the entire cerebrum is manifestly and considerably softer than natural; at other times, only particular portions of it are found in this softened state. Now and then, but very rarely, abscess is discovered within its substance. It is remarkable that the cerebellum is always considerably softer than the cerebrum: whence these two portions of the organ are often observed to be in opposite states, the cerebrum being frequently preternaturally firm, and the cerebellum being almost always softer than natural. The pituitary gland also is very constantly softened, and often in a state of suppuration. When the cerebrum is preternaturally firm, the firmness is usually general. The morbid change observable in the cavities of the brain consists in their containing an excess of secretion. This increase of secreted fluid is usually accumulated in the lateral ventricles: the quantity varies from a drachm to several ounces; when thus great, the lateral ventricles themselves are enlarged, the third and fourth ventricles are likewise distended with fluid, and the passages connecting them are proportionally full. Common as it is to find a preternatural quantity of fluid in the ventricles, it is still more common to find it in excess between the membranes; often between the dura mater and the arachnoid, almost always between the arachnoid and the pia mater. It has been already stated, that the fluid effused between the arachnoid is of a gelatinous appearance and aspect; every where else it possesses the physical properties of serum, being thin, transparent, and of a straw colour: now and then it is thicker in consistence, opake, and even bloody, and sometimes that beneath the membranes contains flakes of lymph, or is mixed with pus.