794 CHRONIC INFECTIOUS DISEASES. 



extreme casss. Moreover, there is an essential difference between the 

 character of the fever in this and other acute infectious diseases. 



In lyssa, among the symptoms are some nervous ones, slightly analo- 

 gous to the neuralgias which occasionally occur, instead of the fever 

 in malarial infection. Lyssa humana most resembles tetanus, although 

 I cannot understand how it is possible to deny the occurrence of lyssa 

 as an independent disease, and to identify it with tetanus. In the 

 well-observed cases, neither continued tension of the spinal muscles 

 nor pain in the contracted muscles has been mentioned, while neither 

 is ever wanting in true tetanus. The difference between lyssa and 

 tetanus is, that the spasms, which may be termed tetanic, only occur 

 in some paroxysms, and are limited to certain nerves, and more par- 

 ticularly to those which are by no means chiefly affected in traumatic 

 or rheumatic tetanus. When Homberg terms lyssa a toxoneurosis, he 

 says all that we actually know of the nature of the disease. 



Without the experience that the poison is reproduced in the body 

 of the patient, we might most reasonably suppose that a toxic neuritis, 

 or a toxic neuropathia, spread from a peripheral nerve, on which the 

 poison had worked, to the medulla oblongata and cerebrum; and, 

 since in many cases changes in the wound or in the cicatrices precede 

 the outbreak of the malady, and the time between these changes and 

 the outbreak is very short, it would be most probable that the poison 

 had remained latent at the seat of injury, but afterward had rapidly 

 spread in a centripetal direction. This latency would most remind 

 us of that of syphilis between the different outbreaks of the disease. 

 However, all this reasoning lacks a solid foundation. 



Lyssa, or rabies, in its stricter sense, is a disease which origi- 

 nates in pnimals of the dog kind, and which indisputably is propa- 

 gated, in most instances, by infection of one animal by another. 

 We shall not discuss the question whether this be its only mode of 

 propagation, or whether, under certain circumstances, it may develop 

 spontaneously. The rabies of other races of animals and the hydro- 

 phobia of human beings are purely contagious maladies. This 

 poison, which exists in the saliva, blood, and perhaps in other 

 fluids of the body, is not volatile, but fixed in character ; it cannot pass 

 through the epidermis, and hence does no mischief, unless brought ir 

 contact with an ulcerated or excoriated surface. 



The most common cause of human rabies is the bite of a mad dog. 

 More rarely the disease originates in the bite of some other rabid 

 animal, such as the wolf, the fox, the cat, or the ox. The possibility 

 of infecting a healthy man by the bite of a man suffering from hydro- 

 phobia has not yet been proved positively ; but the inoculation of the 

 disease from human beings to brutes has reoeatedlv been successful 



