Neuropathology

Pathology of the Cerebrospinal Fluid.—Pathological changes in the cerebrospinal fluid are important in the diagnosis of nervous diseases. Normal cerebrospinal fluid is clear like water; it has a specific gravity of 1.006 and resembles in its com position the blood minus its corpuscular and albuminous constit uents. Being secreted by the choroid plexus, if any cause, such as tumour or meningitis, should interfere with its escape from the ventricles it gives rise by pressure to internal hydrocephalus and cerebral anaemia which may occasion epileptic convulsions and various degrees of drowsy stupor, lethargy, unconsciousness and even coma. Lumbar puncture has proved of some use in treat ment, but is invaluable in the diagnosis of various diseases of the central nervous system. The fluid withdrawn should be centri fuged and the deposit examined microscopically if necessary after staining by suitable methods; the existence of cells indicates dis ease of the central nervous system. In general paresis, cerebro spinal syphilis and tabes dorsalis even in early stages, the deposit consists almost entirely of lymphocytes. Some evidence of the progress of the disease and the effect of treatment may be ob tained by counting the number of cells at different periods. In tuberculous meningitis there are also lymphocytes in abundance; tubercle bacilli cannot readily be found, but if the fluid be in jected into a guinea pig, the animal will develop tubercle. In epi demic cerebro-spinal meningitis the cells in the deposit are poly morpho-nuclear leucocytes and in the leucocytes can be seen Diplococcus intracellularis. Septic, pneumonic and pyogenic or ganisms may also invade the central nervous system giving rise to meningitis, and in these cases the deposit will be polymorpho nuclear leucocytes, and perhaps the specific organisms may be seen in stained preparations; but if not, they can be obtained by cultural methods.

Other formed elements which may be found are large cells, macrophages containing blood pigment ; these cells indicate that haemorrhage has occurred. One of the most important uses of lumbar puncture has been the discovery of the cause of African sleeping sickness. The fluid withdrawn and centrifuged is found to contain large numbers of lymphocytes and plasma cells in addition to specimens of the actively moving organism Trypanosoma gam biense, a flagellate. In the forms of disease here described as containing cells in the centrifuged deposit, there is also in the fluid an appreciable amount of proteins. If pathological cerebro spinal fluid be added to an equal quantity of saturated solution of sodium sulphate there will be a distinct turbidity indicating the presence of proteins in appreciable quantity. This appreciable quantity of proteins is especially significant in the case of fluid withdrawn from cases of general paralysis or tabes, for it goes pari passu in amount with the Wassermann sero-diagnostic reac tion for syphilis.

African sleeping sickness is characterized by a progressive lethargy, paresis, tremors and the signs and symptoms of neural exhaustion without neural destruction; it comes on slowly and insidiously often years after infection and eventually terminates fatally by intercurrent disease or paralysis of the bulbar centres. Examination of the central nervous system explains the fatal lethargy; the perivascular and meningeal lymphatics are filled with lymphocytes and plasma cells and the neuroglia supporting cells have undergone a rapid proliferation. The effect of this morbid

process is to deprive the neural elements of oxygen and nutrition; the neurones in consequence, although not destroyed, are never theless unable to function for more than a brief period.

Poisons Introduced into the Body.

The most widespread and potent cause of nervous and mental disease is the abuse of alcohol-containing liquids. At least 20 per cent of the inmates of the asylums of London are admitted with a history of alcoholism. Whether alcoholism is a cause or a result is still debatable. In not more than io% is alcohol the efficient cause of the mental disease; in many it is only a contributory factor, and in not a few the lapse from moderation to intemperance is one sign of a mental disturbance. To people with unstable nervous systems a relatively small quantity of alcohol may act as a poison. Thus epileptics, imbeciles, criminals, potential lunatics, and the subjects of head injury are liable to become anti-social and dangerous to them selves and others by indulgence in quantities of alcohol which would have no harmful effect upon the mentally stable and sound individual. However, chronic alcoholics form a large proportion of those convicted for crimes of violence, homicide, suicide, and sexual offences. Another common effect of alcohol is peripheral polyneuritis (see NEURITIS), although frequently changes occur as well in the ganglion cells, from which the axis cylinders of the nerves have their origin. (See NERVOUS SYSTEM.) Alcoholic poly neuritic psychosis affecting women in many ways resembles delir ium tremens (see DELIRIUM) ; the fact that neuritis occurs much more frequently in women is probably associated with the fact that when the female breaks through the resistance to her con flicts by the use of alcohol her regression is deeper and her in dulgence greater. Many other poisons, notably lead and arsenic, the specific fevers before mentioned, syphilis and alterations of the blood due to imperfect metabolism, such as occur in diabetes and gout, may produce, or become important factors in producing, peripheral neuritis. The outbreak of arsenical neuritis from beer containing this poison in Manchester in 1900 (see ADULTERATION), is of interest from that fact that the symptoms closely resembled acute alcoholic neuritis. A distinctive feature, however, was the pigmentation of the skin and the severity of the nervous symp toms. A disease, common in the East, termed beriberi (q.v.), is a form of neuritis. Anaesthetic leprosy is an interstitial inflam mation of the nerves due to the Lepra bacillus. Among the ner vous diseases due to occupation may be cited lead-poisoning (q.v.). Lead also produces a chronic inflammation of the cerebral cortex, Encephalitis saturnina, causing a complex of symptoms, namely dementia, loss of memory, weakened intellect, paresis and epilepti form seizures, hallucinations of sight and hearing, and mental exaltation or depression. Mirror-makers suffer with characteristic fine tremors, from the slow absorption of mercury into the sys tem. Workmen at indiarubber factories may suffer from severe mental symptoms, owing to the inhalation of the fumes of carbon bisulphide. Serious nervous symptoms have followed carbon monoxide poisoning. Cases which have recovered from the im mediate effects have suffered with dementia and symptoms of disseminated sclerosis, the result of multiple haemorrhagic sof ten ings.