indications of acute changes, both parenchymatous and interstitial,* have been found in them, although in some cases they have been apparently normal. In addition to the enlargement of the spleen observed during life and found also after death, the mesenteric glands have been found swollen, and also the closed follicles of the intestines. Organisms were found in the glands by Baumgarten, but most observers have searched for them without success in all cases of typical character.

These negative facts, taken in conjunction with the conditions under which the disease occurs, and with the course of the malady, have suggested the idea of a toxic influence acting on the nerve-centres; and this idea receives support from the discovery that acute swelling of the spleen is common, and of the lymphatic glands not rarelesions that indicate a morbid blood-state. The limitation by function of many toxæmic palsies, e. g. that of accommodation, affords confirmation of this view, since the isolated acute paralysis of a functional centre, not anatomically separate from others, is known only as a consequence of a toxic influence. Further confirmation is afforded by the fact that cases of acute multiple neuritis, certainly due to a toxæmia, may run a similar course, and that indications of such commencing neuritis may actually be found in this disease. But this does not exclude a central process. It has, indeed, been conjectured that the nerves are always the structures impaired, but this view is rendered unlikely by the common absence of altered excitability of the muscles, since the motor nerves seem never to escape invariably in peripheral neuritis of any variety, however common their freedom from affection in the type. At the same time this does not exclude the periphery: the nerves may suffer also in some cases, and there may, indeed, be gradations to the cases of acute multiple neuritis of ascending course described at p. 128. If we ask on what nerve-structures this toxic influence is usually exerted, we meet with the difficulty that while it is clearly upon some part of the motor path, the integrity of the muscles shows that the interruption is not in their nerves or nerve-cells, and their relaxation, with the prolonged impairment of myotatic irritability, suggests that the structures interfered with are not far from the motor centres. Curara abolishes the function of the termination of the lower segment of the motor path, i. e. of the nerveendings in the muscles. It may be that, in this disease, some toxic influence impairs in an analogous manner the function of the termination of the upper segment, paralyses the ramification in which, as we have seen (p. 175), the pyramidal fibres must end in the grey matter, and by which they are connected with the lower segment. It has been already pointed out (p. 213) that the nutritional stability of the termination is probably lower than that of any other part of each segment, since it is the part furthest from the nerve-cell from which the fibre proceeds, and on which its nutrition depends. The greater Eisenlohr, Deut. med. Wochenschr.,' 1890, No. 38.

length of the fibres for the lumbar region may render their termination more susceptible than that of the fibres for the arm, and hence the ascending course of the paralysis. It is, moreover, readily conceivable that the effect extends in slight degree to other structures in the grey matter-those, for instance, which intervene between the sensory and motor cells; and thus the loss of reflex action and myotatic irritability is explained, as well as the muscular relaxation, since, as we have seen, muscular tone must be ascribed to a reflex process. The structures affected may vary somewhat in different cases, and thus the state of reflex action may vary. The facts of diphtheritic paralysis also show that the effects of such a toxic influence may be revealed, in varying degree, by visible changes having the characters of inflammation, and we can thus understand that indications of such inflammation in the

grey matter may be occasionally met with. The bulbar symptoms come under the same explanation. The motor path through the nuclei of the medulla has the same pathological relations as that which passes through the grey matter of the spinal cord. The separate affection of nerve-structures, distinct from others only in function, is common in the phenomena of toxic actions. There are no facts to show the nature of the blood-state, except those that suggest its alliance with the influences that act on the peripheral nerves; multiple neuritis should be studied in connection with this disease. These facts suggest that the virus is a product of the preceding growth of organisms, at least in some cases; and if so, it is natural that the organisms themselves should not be found.

DIAGNOSIS.-The disease is recognised by the rapid development of paralysis, usually ascending, with relaxation of the muscles, and with loss of reflex action, without considerable pain or loss of sensation, and if the patient survives, without wasting of the muscles or change in electrical irritability. The latter characteristic distinguishes the disease from acute atrophic paralysis, while the absence of pain in the back and of spasm is a distinction from meningeal hæmorrhage. The diagnosis from general ascending myelitis has been already considered; it rests especially on the involvement of all the functions of the cord in inflammation. The distinction from multiple neuritis has been mentioned in the account of that disease (p. 140), but, it may be, is not always absolute, since the nerves probably suffer, as well as the cord, in some cases of ascending paralysis. The distinction from polyneuritis, founded on the course of the ascending form, is subject, moreover, to the reservation that while ascension to the arm through the trunk is a feature of the central disease, this is not excluded by a more irregular course, and the character of the individual symptoms must be taken into consideration (see also p. 383).

PROGNOSIS.—The affection is one of extreme gravity. The danger to life is in proportion to the interference with respiration and with the functions of the medulla oblongata, especially with the cardiac centre, and also to the rapidity with which the palsy comes on. But

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the cases which develop with comparative slowness are not devoid of danger. Even when the symptoms only reach their height at the end of three or four weeks, death may occur in the same way as in the more rapid cases. On the other hand, recovery has been known although the patient has lost all power of motion at the end of the second day. The danger is great as long as the symptoms are increasing, and only when distinct improvement can be recognised is it justifiable to anticipate recovery. The earlier the bulbar symptoms appear, the more serious is their significance. Mental symptoms also increase the gravity of the prognosis, as they usually indicate a severe blood-change, the effects of which on the nervous system are likely to reach a high degree.

TREATMENT.-During the early stage of an attack of acute ascending paralysis, in the absence of other indications, the treatment should be that suitable for myelitis, since, at the onset, the diagnosis between the two diseases can never be certain. A warm bath, or still better, a vapour bath, should be given if the symptoms followed exposure to cold. It should be followed by counter-irritation over the spine by a long, narrow mustard plaster. More energetic counter-irritation, even the actual cautery, has been recommended. The body should be kept in as perfect rest as possible. In a very few cases have drugs appeared to exert any influence on the course of the disease, and the malady is so rare that experience accumulates slowly. Salicylate of soda seems to deserve a trial in cases that follow exposure to cold. Ergotin has been given, and one case in which it was used deserves special mention. The patient was a man aged fifty-seven, who, a week after exposure to cold and wet, complained of a feeling of weight and weakness in the legs; the temperature rose to 103°; the loss of power gradually became complete in the legs and spread to the arms, without loss of sensation. At the end of the second day there was difficulty in swallowing, in articulation, and in breathing, and death. seemed near. Ergotin was given every hour, and during the night the patient took twenty grains. In the morning the bulbar symptoms were better, the arms stronger, and there was a trace of motor power in the legs. The patient rapidly improved, and at the end of a week was well. If swallowing becomes difficult, care must be taken to administer a sufficient amount of nourishment, either by the rectum or by the nasal tube. Several cases have been recorded in persons who had had syphilis, in whom arrest of the disease followed the administration of iodide of mercury. The chief lesson of modern researches is certainly that we must look for the means of effective treatment to the neutralisation of the toxic influence on which the malady apparently depends. At present, however, nothing has been ascertained regarding antidotal agents available in the acutely active stage of these toxæmic states. It is, however, probable that mercury is capable of doing this in some cases, and that when the causation is obscure, and the disease develops slowly enough to permit mercurial

treatment, it is wise to adopt this irrespective of the fact of preceding syphilis. In cases that follow traumatic lesions, especially if there have been any indications of septicemia, full doses of perchloride of iron offer, I believe, the best means of destroying the activity of the blood-state. Urgent symptoms require the same treatment as in myelitis.

PARALYSIS FROM LESSENED ATMOSPHERIC PRESSURE; DIVERS' PARALYSIS.

Divers, and especially those who work in caissons, at such a depth beneath water that they are exposed to considerable pressure, may become paralysed soon after their return to the surface.* Apoplectic attacks and hemiplegia also sometimes occur, but paralysis of the legs is by far the most common effect, and it is, therefore, clear that the spinal cord suffers in greater degree than any other part of the nervous system. Miners have been said to suffer also, but this is doubtful, because a pressure equal to at least an additional atmosphere seems necessary for the production of the symptoms. Most of the subjects of the disease have worked at a depth of from forty to ninety feet below the surface of water, and under a pressure of two to four atmospheres. In the extensive works involved in laying the foundations of bridges, in which many men have been employed, a considerable proportion of the workers have suffered in some measure; but severe degrees of affection are rare, because the conditions under which they occur can be avoided. They only occur in those who have been exposed for more than a certain time, which is the shorter the greater the pressure. At a depth of ninety feet beneath the surface, immunity from severe symptoms (and commonly from all symptoms) is obtained by reducing the periods of work to an hour. The danger is greater in those who have had several previous periods of work on the same day, and especially if slight symptoms have been experienced after one of these. It is also greater in those unaccustomed to the conditions. I have met with one case of hemiplegia in a diver after only half an hour's work in a well at ninety-six feet, but the man had been down twice before with only intervals of rest of half an hour, and the attack passed off in the course of an hour. In another case paraplegia occurred after working for an hour under only fifty feet of

See, on this subject, Babington and Cuthbert, Dubl. Quart. Journ.,' 1863, p. 312 (cases at Londonderry); Eads, Med. Times and Gaz.,' 1871, p. 291 (cases at St. Louis); Leyden, Arch. f. Psychiatrie,' ix, Heft 2; and Moxon, Laucet,' 1881, ii, 529.

water, but the man had worked on the preceding day at a depth of one hundred and twenty feet below the surface. It is evident, therefore, that the power of resisting the dangerous influence varies, and that predisposition to suffer may be caused by the conditions which also induce an attack.

It is not during exposure to the abnormal conditions, but on returning to the normal atmospheric pressure, that the symptoms come on; often immediately, and always within half an hour or at most an hour of the return to the surface. The onset is usually preceded by other symptoms, and especially by pains in the ears and in the joints. The latter is very common, and occurs after a much slighter degree of exposure than is needed to produce paralysis. They are felt chiefly in the larger joints, and may continue for days and even longer. Very rarely there is also swelling of the joints.

It is important to note the conditions under which the symptoms come on. Not only do those who are unused to such work seem especially liable to suffer, but there are also considerable individual variations in the degree of liability.

Paraplegia or hemiplegia may occur, but the former is far more common. The onset of the paralysis is sudden. The legs feel heavy and are found to be weak, and in a few minutes the patient is unable to move them. Sensation is often lost as well as motion, and in all severe cases the sphincters are affected. The arms are seldom involved. In slight cases the loss of power is incomplete, and one leg may be more affected than the other. The impairment of sensation is often imperfect or irregular. If the paralysis is incomplete the power may return in the course of a few days, but in severe cases the palsy usually lasts for weeks or even months, and it may be permanent. Death may occur at the end of a week or more, in the same way and from the same causes as in acute myelitis. When the paralysis is hemiplegic it is generally moderate in severity and transient, passing off in a few hours or days. It may be even still more brief, as in the case referred to above, in which a diver, after half an hour's work ninety-six feet below the surface, suddenly felt tingling across his loins, and that his right arm and leg were almost powerless; in half an hour he had recovered sufficiently to walk home. If cerebral symptoms are more intense, they are generally very severe, with sudden loss of consciousness, continuing as deep coma, irregular breathing, and indications of cardiac paralysis. Such cases usually end in death in the course of a few hours.

PATHOLOGY.-The most probable explanation of these cases ascribes them to the escape from the blood of gases, with which it has become charged during the exposure to the high pressure. It is certain that a great excess of gas must be dissolved in the blood during the exposure, and that the amount, at least of oxygen and of carbonic acid, contained in the blood when the person emerges from the caisson must be vastly greater than normal. It must, moreover, be greater the