The cord may be the seat of an effusion of blood, and rnay thus present the condition of apoplexy, like that m hich is of so frequent occurrence in the brain. In such cases there may be more than one small clot occupying the central part of the cord. They are of rare occurrence, and are generally found in the upper part of the cord.
Tubercle may occur in the cord, and, as in the brain, connected with the pia mater, either deposited in a group or forming a mass whidi gradually encroaches upon the substance. The cervical region is that in which it most fre quently is found, and it forms tumours of va rious sizes, each of which is generally enclosed in membranous cyst.
Cancer of the cord is a lesion of extremely rare occurrence. 011ivier relates several cases of it, but Rokitansky remarks that he has seen but one example of a cancerous tumour in the spinal cord. It is in cases where the cancerous diathesis prevails, and where cancerous matter is deposited throughout various parts of the body, that we may look for it in the cord.
Abnormal anatomy of the brain and its mem branes.—The remarks already made with re ference to the membranes of the cord apply equally to those of the brain. The latter mem branes, however, are more frequently found in an abnormal state than the former.
The dura mater.—There may be a general or partial deficiency of the dura mater and of the other membranes according as there is a general or partial defect in the brain itself.
The partial defect is mostly observed in the falx cerebri or in the tentorium cerebelli. The cribriform appearance of the former process is of frequent occurrence and is unaccompanied by any obvious defect in the brain, and some times even a considerable portion of it is want ing, while the brain is quite normal.
Acute disease of the dura mater is rare, and only occurs as an effect of wounds or injuries of the cranium, or in connection with syphilitic or strumous disease of the bones ; or, inde pendently of diseased bone, as an effect of the syphilitic poison, like that which occurs on ex ternal fibrous membranes. A syphilitic in flammatory state of the durarnater is frequently the cause of serious affection of the brain. A condition analogous to that of node will cause pressure on the brain and paralysis ; and, whilst it resists the ordinary antiphlogistic treatment,will speedily yield to antisyphilitic re medies, such as mercury and iodide of potassium.
We meet with great variety as regards the firniness of adhesion of the dura. mater with the cranium. There is a tendency in some perverted states of nutrition for this membrane to become incorporated with the inner table of the skull. This seldom takes place conti nuously, but in patches, so that in removing the calvaria a portion of the inner table of the skull remains in connection with the fibrous mem brane, or a hole is left in the latter when the conversion of the fibrous membrane into bone may be complete. It is in the more advanced periods of life that this mor bid condition is chiefly found ; indeed we seldom open the skull of a person who has passed the age of threescore without finding more or less of it. At that period of life it may be regarded rather as one of the series of changes which accompany advancing years than as a diseased state. When, however, it occurs at the earlier ages, it must be viewed as resulting from a morbid process.
Patches of bone are frequently found in the processes of the cranial dura mater, as in the falx, tentorium. They occur more frequently in the former than in the latter. In size they vary much : they are placed between the layers of the dura mater, and are completely enclosed by,them ; sometimes, however, they encroach upon these layers, which then seem as if they had been completely converted into bone.
Fibrous tumours are sometimes formed at various parts of the dura mater. These vary considerably in size and number. They pro ject inwards upon the brain, and indent that organ more or less according to their size, and sometimes they project outwards, and by causing absorption of the bone by pressure form depressions for themselves, and even wear holes in the bone by their outward growth.
Tubercles of a strumous character are some times deposited in connection with the dum mater. The most remarkable example I have seen of these morbid tumours is a preparation in the museum of King's College, London, taken from a patient who suffered severely from epilepsy. The internal surface of the dura tnater and of the falx is covered with numerous tumours of this kind, some of which are nearly as large as a walnut, others not larger than a small filbert. This specimen belonged to the collection of the late Dr. Hooper, who has given an excellent delineation of it in his plates of the morbid anatomy of the brain.