783 



HYDROPHOBIA. 



HYDROSTATICS. 



78G 



licked the hand or face of a person on which there was any raw 

 surface. However, it is only a small portion of the bites which a mad 

 animal gives that convey the disease ; if, for example, he bites through 

 the clothes, there is a great probability that all the saliva will be wiped 

 off from his teeth as they pass ; and hence wounds of the hands and 

 face are generally the most dangerous. It is probable, too, that the 

 saliva differs in the degree of its virulence in different animals ; the 

 bite of the mad wolf seems generally more fatal than that of the dog. 

 In a case known to John Hunter, twenty-one persons were bitten by 

 the same dog, and only one had hydrophobia ; in another, a wolf bit 

 seventeen persons at Brive, and of these ten died by hydrophobia ; in 

 a third, fifteen persons were bitten by a dog, in ten of whom the wound 

 was on the flesh, and three died. In none of these cases had any pre- 

 ventive measures been used ; and from the evidence collected from 

 various sources, Dr. Hamilton (' Remarks on Hydrophobia/ vol. i.) 

 thought that whether preventive means were employed or not, only 

 one person in twenty-five of those bitten by mad dogs would have 

 hydrophobia. It appears that animala are more subject to the disease 

 than man ; for in a case where a dog bit four persons and twelve dogs, 

 all the dogs died, but not one of the men. These results, although 

 they should not prevent the surgeon from employing those measures 

 which prevent the disease, fully explain how empirical remedies have 

 obtained so much credit, the immunity from the disease being attri- 

 buted to their influence, when it would have been as complete if they 

 had never been used. 



The period after the inoculation at which the symptoms of hydro- 

 phobia may exhibit themselves varies greatly. In the ten persons 

 already mentioned who were bitten by the wolf, one was affected on 

 the sixteenth and another on the sixty-eighth day after their wounds 

 were received ; in the five bitten by the same dog, the deaths occurred 

 between the thirtieth and sixty-third days. In general the disease 

 appears between the thirtieth and fortieth days from the injury ; but 

 cages are known where it has been delayed as long as eighteen months, 

 and Dr. Bardsley believes that a person who has been bitten and used 

 no preventive measures cannot be considered as perfectly safe till at 

 least two years have elapsed. Cases are indeed recorded in which there 

 was no evidence of injury for ten and twelve years before the disease 

 manifested itself, but at present neither the number nor the accuracy 

 of such histories is sufficient to allow any safe conclusion to be drawn 

 from them. 



The bite of a rabid animal generally heals up like that of a healthy 

 one ; there is nothing whatever which would indicate danger from it, 

 and the patient is attacked when he has forgotten that he was ever 

 bitten. In some cases, however, before hydrophobic symptoms appear, 

 the scar of the wound becomes painful, red, and swollen, and pain is 

 felt shooting from it along the course of the nerves of the part, as if it 

 were going to ulcerate. The first decided indication of the disease is 

 that the patient has headache and general uneasiness ; he loses his 

 appetite, and when he is about to drink he suddenly feels an aversion 

 to any liquid, and is choked by any attempt to swallow it. He gene- 

 rally discovers this inability to drink accidentally, and often expresses 

 his wonder that he should not be able to quench his thirst. The 

 symptoms, once set in, rapidly increase in severity ; any attempt to 

 drink, and even anything that can suggest the idea of drinking, as the 

 sound of liquid poured from one vessel into another, or the bright 

 shining surface of polished metal looking like the surface of water, is 

 sufficient to bring on the most frightful spasms of the throat, threatening 

 instant suffocation, and producing the most severe pain. The convul- 

 sions, which were at first limited to the muscles of the throat and of 

 deglutition, after a short time extend to other parts of the body ; 

 there is a constant agitation of the limbs, and a remarkable degree of 

 nervous excitement ; the patient is restless, anxious, and timid ; his 

 eye has a peculiarly unsteady glistening appearance, and he is often 

 delirious, and talks with the greatest rapidity and earnestness to 

 persons who are not pesent, or he thinks that his attendants are going 

 to rob or murder him, and is haunted with frightful visions. As the 

 disease proceeds, the convulsions of the throat become more frequent 

 and severe ; a breath of cool air, or the slightest noise or vibration of 

 the room, is sufficient to excite them : there are severe headache, a 

 rapid pulse, a foul tongue, and other symptoms of a generally disordered 

 condition of the system. A copious secretion of thick tenacious mucus 

 clogs up the air passages, and increases the feeling of suffocation, and 

 it is in his attempts to free himself from this that the patient coughs 

 and makes a loud harsh noise, which has been supposed to resemble 

 the barking of the animal by which he was bitten. Sometimes there 

 is furious delirium ; but often for the last few hours of life the patient 

 becomes quiet : he falls perhaps into a tranquil sleep, as if fatigued by 

 his exertions, or he lies perfectly still, without spasms, and rational ; 

 but it is only a deceptive calm which presages his death ; he rouses 

 from his tranquillity, and, after one or two comparatively slight con- 

 vulsions of the throat or of the whole body, expires. The duration of 

 the disease is very rarely more than six days, and it often terminates 

 fatally in twenty-four hours. In the latter cases the patient usually 

 dies suffocated by one of the spasms of the throat ; in the former he 

 may have several remissions, in which the severity of the affection 

 greatly decreases, and which may for a time seem to afford a hope of 

 recovery. In moat canes solids can be swallowed without much diffi- 

 culty ; and it is remarkable that hi those who have been bitten by mad 



ARTS ASD SCI. DIV. VOL. TV. 



cats there is far less aversion to water than in those who have received 

 the disease from the other species. 



Nothing can at present be regarded as certainly known of the true 

 nature of hydrophobia. Dissections of those who have died of it have 

 shown the effects, but not the causes of its symptoms ; as redness and 

 turgescence about the throat and larynx, and general congestion from 

 the frequent suffocative attacks. With this ignorance of its nature 

 there is unfortunately an equal ignorance of any mode in which it may 

 be treated with a prospect of success ; for of all the medicines recom- 

 mended (and probably no disease has been more variously treated) 

 there is not one which has sufficient evidence to prove that it has been 

 of the least avail, except in temporarily mitigating the symptoms. 

 Opium in very large doses will produce quietude and great comfort to 

 the patient by warding off the attacks of spasm, and will prolong, 

 though it will not save life ; and large bleedings have been useful in 

 lessening the severity of the convulsions, and large doses of hydrocyanic 

 acid have controlled the symptoms for days. But the only question 

 that can be satisfactorily considered is that of prevention, which is 

 accomplished by the removal of the morbid saliva from the wound 

 before it has had time to produce its fatal influence on the body. 

 Excision is at once the safest and most simple means, and whenever it 

 is practicable should be employed as early as possible ; the parts bitten 

 should be completely cut out, with some of the sound tissues around 

 them, and care should be taken that the very bottom of the wound is 

 removed ; for if a portion of the wounded surface remain, the patient 

 is not secure. In some cases, however, as where the wound is super- 

 ficial but extensive, or where it is situated on the face, or near an 

 important organ, excision may be deemed unadvisable, and in these the 

 best remedy is some violent caustic : pure nitric acid, or fused potash, 

 or nitrate of silver, should be applied freely over the whole surface of 

 the wound, so as to decompose every particle of the saliva. A third 

 means is the careful washing of the wounds, but it is one on which 

 it would be imprudent entirely to rely, though it should always be 

 diligently employed until medical assistance can be obtained, and is 

 useful after the parts have been cut out. The best mode of washing 

 the wound is to pour water at a temperature of 90" or 100 on it, from 

 a height of four or five feet, through the spout of a tea-kettle, and it 

 should be continued for two or three hours, unless the other means 

 are resorted to. It is not yet known at how late a period after the 

 infliction of the injury it would be useful to remove the parts bitten ; but 

 considering the length of tune during, which the poison remains latent, 

 and the probability that during that time it has only a local influence, 

 it would certainly be prudent to remove the wounded parts after a 

 lapse of even many days. Of course the value of these means is open 

 to the objection already mentioned, that even when the patient does 

 not suffer from hydrophobia it is uncertain whether his immunity 

 depends on the measures employed ; but it may be sufficient to state, 

 that while every other remedy has frequently been unavailing, 

 excision, when carefully employed, has been invariably successful, and 

 the caustic has very rarely failed. 



As a large majority of the cases of hydrophobia which occur in this 

 country are the consequence of the bite of the mad dog, it may be 

 useful to add the symptoms which he presents when in that state. He 

 grows sullen and snarly ; he leaves his home and runs about wildly, 

 biting at whatever approaches him, though he\ will seldom go out of hi* 

 way to attack, and he constantly gnaws grass and straws and pieces of 

 wood or stone. To those, however, with whom he associates his 

 demeanour is at first unaltered, and he caresses them as usual ; and 

 hence the cases in which death has followed the licking of a wound by 

 dogs who showed no symptom of hydrophobia. It is an error to 

 imagine that the mad dog avoids the water, for he will both drink it 

 and swim in it as usual, and without presenting any of that horror of 

 it which characterises the disease in man. Towards the close of the 

 disease he grows more furious, gnawing and biting at everything 

 around him, and frothing at the mouth. The disease is as incurable 

 in the dog as in man, and usually lasts about the same length of 

 time. 



HYDROP3 PERICARDII, or HYDROPERICARDIUM (from 

 SSup, water, and trtpiKitpitov, the pericardium), is a collection of an 

 unnatural quantity of fluid in the sac containing the heart. [HEART, 

 DISEASES OF.] 



HYDRORHODEORETIN. [CouvoLvuuc ACID.] 

 HYDROSTATIC BALANCE. [SPECIFIC GRAVITY.] 

 HYDROSTATIC BELLOWS. [HYDRODYNAMICS.] 

 HYDROSTATICS is the science which relates to the pressure and 

 equilibrium of the fluids commonly called non-elastic, or incompressible, 

 as water, mercury, &c., and to the equilibrium of bodies immersed in 

 them. The elastic fluids, as air, steam, &c., are the subjects of 

 pneumatics. 



The two books of Archimedes, entitled, in Latin, 'De Humido 

 Insidentibus,' contain all that is known concerning hydrostatics, properly 

 so called, among the ancients. That philosopher showed from experi- 

 ment that a mass of fluid will be in equilibrio when each of its particles 

 is pressed equally in every direction. He explained that a floating 

 body is held in equilibrio when its centre of gravity and that of the 

 displaced fluid are in one vertical line ; and that when bodies are 

 immersed in a fluid of less specific gravity than themselves, they lose 

 certain portions of their weights. The latter principle led him to the 



