DIAGNOSIS.—The diagnosis of rabies and hydrophobia is not usually difficult if the disease has progressed to its paroxysmal stage. The most pathognomonic features are the fact of a bite by a rabid animal and the evidence of lesions and an extraordinary irritability of the medulla oblongata, inducing severe reflex spasms of the muscles of deglutition and respiration under the influence of any peripheral irritation. The clonic nature of the spasms and the entire absence of trismus serve to distinguish it from tetanus. From pharyngeal anthrax and diphtheria attended with spasm it is diagnosed by the extreme exaltation of the special senses and the absence of any marked febrile reaction; from acute mania by the difficulty of breathing and deglutition, the more rapid heart-beats during a paroxysm, and by the marked hyperæsthesia and exalted reflex susceptibility, as well as by the perfectly lucid intermissions; and from epilepsy, in that the latter is not associated with the same hyperæsthesia, that the paroxysm is not developed by noise, movement, attempts to swallow, sight of water, etc., that the spasms are more universal, and that they do not recur often, nor can they be roused by the causes immediately producing those of hydrophobia. Hysterical cases can usually be recognized by the imperfection of the symptoms; the subject, not knowing all the manifestations of hydrophobia, naturally fails to produce them.
The most difficult to distinguish from the genuine disease are those cases in which hydrophobia occurs as a disease of the imagination, the result of fear—the lyssophobia or hydrophobie non-rabique of the writers. In these there is always the history of a bite; the cicatrix even may have become the seat of congestive redness, itching, or neuralgic pains, and these, acting on a susceptible brain, develop a disease which is hardly distinguishable from true hydrophobia, and which is quite as fatal if left to run its course. These cases have usually less reflex susceptibility than genuine hydrophobia; the attack mostly occurs shortly after some conversation on the subject, and especially about the effects of the bites on others; and the victim is seen to have a nervous organization, and may even be known to have been subject to hysteria or other nervous disorder. At the same time, the concentration of the mind on this subject sometimes produces even structural changes in the medulla, and the reflex susceptibility in co-ordination with the other symptoms may be almost perfect. In a case reported a few years ago by Hammond the symptoms appeared perfectly characteristic, and at the necropsy circumscribed points of congestion were found near the roots of the vagus; yet the dog that bit this man was said to be alive and well, and in the absence of any successful inoculation from biter or bitten the case must be presumed to have been lyssophobia.
Many cases with a more favorable issue are recorded. Bellenger had a patient who had been bitten by his cat, and manifested violent paroxysms of hydrophobia, but was instantly cured by the sight of the animal in good health. Bouardel records that a man was bitten by his dog, which afterward disappeared. He was seized with severe hydrophobia, which continued for two days, when the lost dog was found and presented to him, and the symptoms disappeared. Trousseau speaks of a magistrate whose hand had been licked by his hound, which immediately after attacked a flock of sheep, so that many of them died of rabies. The master then manifested hydrophobia, but as death was deferred beyond the usual time, he concluded it was not genuine and recovered. Prof. Dick was called to visit a man who had been bitten by a favorite dog while suffering from distemper, had manifested severe hydrophobic symptoms, and had been given up by the attending physicians. He succeeded in convincing the subject that as the dog had had distemper, and as no two great diseases could coexist in the same system, it could not have had rabies. In spite of the false premises, this reasoning had the desired effect and the patient recovered. A few years ago a boy twelve years old in Ithaca, N.Y., was bitten by a dog supposed to be rabid, and in due time manifested hydrophobia, which advanced rapidly until he was having a violent paroxysm every half hour, and it was pronounced impossible for him to survive another day. At this time I saw him, observed that he had a nervous organization, and was somewhat lacking in the hyperæsthesia of rabies, learned that he had recently been gorging himself with Christmas delicacies, and was now very costive; and, as there was no satisfactory history of the dog, I at once suspected lyssophobia. The friends and strangers who had come to condole with the parents and feast on the horror were excluded, and the boy's attention fully engaged in amusing pictures and conversation; the paroxysms were omitted, and in two hours the patient, overcome by weariness, went to sleep. Next morning he was still kept secluded and quiet, and two enthusiastic students took up the rôle of keeping his attention constantly engaged on whatever would interest him. The prima viæ was relieved by medicine, and under a course of tonics the boy quickly recruited, and at the end of a week went back to school.
In doubtful cases the test by inoculation may be tried. Inoculation with the saliva of a man suffering from hydrophobia is manifestly useless, since he must die before we can hope for the development of the disease. But in the case of a dog having bitten one or more people the inoculation of the virus on the brain of one or two other dogs would ensure the development of the affection in the course of one or two weeks, provided the first was rabid. The non-success of this operation when practised on two dogs would provide the best possible medicine for the diseased mind of the person bitten.
PATHOLOGICAL ANATOMY.—Post-mortem lesions are rather remarkable for their inconstancy than for their specific characters. Hardly a single lesion can be specified which may not be absent in particular cases, yet some are so characteristic that, when taken along with the symptoms during life, they very materially assist in diagnosing the disease. Of the pathological appearances common to man, dog, and other animals the following may be named: The body is greatly emaciated; the rigor mortis is normal or nearly so; decomposition usually sets in early; a white skin is livid, cyanotic, or petechial; the cicatrix is often hardly noticeable even after the animal has been shaved; the superficial veins, especially those of the neck and head, are filled with black inspissated blood; the external mucous membranes are of a dark livid hue, those of the mouth and nose being covered by a tenacious mucous or muco-purulent secretion (in dogs they are usually covered with earth or dust); the fauces, pharynx, and tonsils are usually of a dark livid hue, and sometimes swollen; in other cases the dark red hue and manifest swelling that obtained during life disappear after death; similar lesions are found in the larynx, and I have seen extensive erosions; the bronchial mucous membrane is reddened and coated with a muco-purulent secretion (and in dogs with earth and foreign bodies); the lungs are usually congested, often to the extent of showing death by asphyxia; the heart and large blood-vessels are filled with a black thick, venous blood, and the muscles, charged with the same blood, have a dark reddish-brown hue; the stomach is usually congested, sometimes to a port-wine hue, and is the seat of blood-extravasations and even erosions; this congestion is often present, though to a less degree, in the intestines; the mesenteric glands and those in the vicinity of the pharynx are not unfrequently enlarged and congested; a very constant feature is the entire absence of proper food in the stomach and of chyme in the small intestine; the liver is usually hyperæmic, exuding on pressure the characteristic dark blood, and it may be the seat of some granular degeneration, but it usually retains its normal consistency; the spleen is normal; the kidneys are hyperæmic and leaden or bluish gray, and slightly cloudy on the surface (in dogs fatty degeneration of the inner cortical layer is common even in health); the urinary bladder is usually empty or contains a little turbid, yellowish, slightly albuminous urine, while the mucous membrane is often covered with dark reddish-brown petechial spots; the brain is usually hyperæmic, and, together with its membranes, slightly oedematous, yet the lesions are not constant either in kind or degree; the medulla oblongata usually shows a similar condition, and even minute points of acute congestion, but neither these nor the hyperæmia and oedema of the spinal cord can be found in every case.
Some conditions are especially pathognomonic in the dog. In nearly all cases of furious rabies the stomach is gorged with foreign bodies, such as hay, straw, wood, coal, leather, portions of textile fabrics, fæces, earth, sand, stones, pieces of iron, lead, etc., and the same materials are usually found in the small intestine, while the large intestines are empty. Portions of these foreign bodies are often found in the bronchia as well, giving rise to circumscribed lobular pneumonia. The significance of such matters when found in large amount in the stomach of a dog which has been given to biting or other symptom of rabies is very great, and if the stomach contains none of the natural food of the animal and the duodenum no chyme, it may be held pathognomonic of rabies. If, however, the materials are small in quantity and mingled with natural food, and if the duodenum contains chyme, the dog was probably not rabid. Dogs frequently chew and swallow fresh leaves of grass, and those in detention gnaw and swallow pieces of wood, cloth, horn, etc.; but these are used either as an emetic or a teething-ring, and virtually imply that digestion is not entirely abolished. Their presence, therefore, along with food does not indicate rabies.
PROPHYLAXIS.—In view of the almost or quite constantly fatal issue of rabies in man and animals, the main attention should be given to the question of prevention. As the disease is perhaps never in our time developed except as the result of contagion, we have the most perfect guarantee that by suitably devised measures it may be absolutely suppressed and excluded from any country. Even if we allow that a rare case is at long intervals developed spontaneously, it is none the less certain that the disease can be practically abolished, as nothing can be easier than to nip the disease in the bud in the locality where it first shows itself. Thus in Australia, Tasmania, and New Zealand rabies has not yet appeared, though prevailing in the same latitude and climate in both hemispheres. It reached Mauritius in 1813, and has prevailed uninterruptedly since, while in Bourbon, immediately adjacent and almost identical in geology, climate, flora, and fauna, it is still unknown. The same truth is told in the entire extinction of rabies in Berlin by the universal muzzling of dogs, as recorded above. The immunity lasted for nine years, during which muzzling was enforced. A more recent example of the same kind is found in Holland. In 1875 universal muzzling was made obligatory in all communes where rabid animals had been and in adjoining communes. From 1877 on the disease was unknown save on the borders of Belgium and Prussia and in a very few dogs recently imported. Nearly all cases of hydrophobia in man and animals being due to bites by rabid members of the canine fraternity, a fundamental condition of all success in prevention is the prohibition of its diffusion by dogs. For this reason the following measures are requisite: 1st. All dogs should be registered and heavily taxed. The number of useless dogs kept in every community affords the greatest opportunity for the speedy diffusion of the rabid germ whenever that has been introduced. Whatever tends to reduce this number directly tends to the restriction and extinction of rabies. 2d. Every dog should be made to wear a collar with plate bearing the name and residence of his owner. All stray dogs without such badge should be summarily shot by the police. This will secure the payment of the taxes and the destruction of superfluous and dangerous dogs. 3d. In all cities and counties where rabies has existed within a year, and in the counties adjoining them, every dog should be muzzled except when securely shut up or tied. All dogs found at large without a muzzle should be promptly shot by the police. The objection to muzzles is satisfactorily met by the use of the wire muzzle, which impedes neither breathing nor drinking. 4th. Dogs and cats suspected or known to have been bitten by rabid animals should be at once destroyed, or if considered sufficiently valuable may be confined in a secure cage for six months under veterinary supervision. 5th. Dogs which have bitten and are supposed to be rabid should be similarly caged and placed under veterinary supervision. If rabid, the symptoms will be fully developed in a few days, whereas if destroyed at once the bitten party is liable to develop lyssophobia. 6th. Dogs imported from countries where hydrophobia is known to exist should be subjected to a period of quarantine of six months. 7th. Foxes, wolves, badgers, martens, skunks, must be indiscriminately destroyed in localities where they have become infected with rabies. 8th. The disinfection or burning of the kennels where rabid dogs have been is a natural corollary of the above.
Other measures less thorough and efficient are often advocated and resorted to, but should be discarded whenever it is possible to practise a method of absolute extermination. Among these may be named the flattening of the teeth, and especially of the canines, with a file, as advocated by Bourrel, and later by Fleming. While this is a measure of protection, it does not remove the desire to bite, nor the power of wounding the skin when that is delicate or tender. Another method is to hang a block of wood from the neck, so that it may impede the movements of the forelegs and prevent a rush and sudden attack. The futility of such a resort need hardly be remarked upon. The emasculation of dogs is another preventive measure advocated. The single advantage of this is that it does away with the host of suitors that follow a rutting bitch, and the mutual worrying and biting that ensue. But it is not yet proved that the disease is produced by privation of the generative act, while if it were it is still certain that cases of spontaneous rabies are extremely rare; that the rabid dog bites the castrated one as readily as the perfect male; that the emasculated one contracts rabies as readily as others when bitten, and that he communicates it no less persistently. Galtier's method of intravenous injection of the rabic saliva, which seems to have proved effectual in sheep and rabbits, utterly failed in the hands of Lussana and Pasteur in dogs. Besides this objection, that it is useless for the animal which is beyond all comparison the main propagator of rabies, it has the serious disadvantages that its practice would necessitate the maintenance of a constant succession of cases of rabies, that great danger attends this production and handling of the virus, and the expense and risk of a general application of the measure must absolutely forbid it.
More recently Pasteur has found that the virus when transmitted through several monkeys in succession becomes so weak as to be harmless to the animal inoculated, and yet protects the animal against the more virulent poison. This fact he utilizes by inoculating this mitigated ape-virus on the brain of the animal just bitten, so as to render that refractory to the disease when the poison from the bitten wound shall reach it by its ordinary slow channel. At the time of writing, the method is being attempted on a man bitten by a mad dog.
Another precautionary measure which is always in place is the diffusion among dog-owners of correct information as to the premonitory symptoms of rabies, and the necessity for careful seclusion when any such symptoms are manifested.