420 THE QUESTION OF IMMUNITY AND ANTITOXINS 



Although rabies was mentioned by Aristotle, and has been studied 

 by a large number of workers since, the contributions of Pasteur 

 have been greater than all the other additions to our knowledge of 

 the disease put together. Professor Eose Bradford has pointed out 

 that Pasteur's discoveries concerning rabies may be said to be four 

 in number : (a) that the virus was not only in the saliva, but also in 

 the central and peripheral nervous system, yet absent from the 

 blood; (b) that the disease was most readily inoculated in the 

 nervous system; (c) that by suitable means the virus could be 

 attenuated ; and (d) that by means of an attenuated virus preventive 

 and even curative methods might be adopted. 



The disease takes two chief forms: (1) furious rabies, and (2) 

 paralytic or dumb rabies. The former is more common in dogs. 

 The animal becomes restless, has a high-toned bark, and snaps at 

 various objects; sometimes it exhibits depraved appetite. Briefly, 

 the animal passes from a melancholy to a maniacal and then a 

 paralytic state, ending in coma and death. In man, the incubation 

 period is fortunately a very long one, averaging about forty days. 

 Nervous irritability is the first sign; spasms occur in the respiratory 

 and masticatory muscles, and the termination is similar to rabies in 

 the dog. The symptom of fear of water is a herald of coming 

 fatality. 



Although a number of the workers at the Pasteur Institute and 

 elsewhere have addressed themselves to the detection of a specific 

 microbe, none has as yet been found, although, in the opinion 

 of Pasteur, such an agent may be suspected as the cause. 



Pathologically, rabies and tetanus are closely allied diseases, and 

 the recent remarkable additions to our knowledge of the latter 

 disease only make the similarity more evident. There are in rabies 

 three chief sets of post-mortem signs. First, and by far the most 

 important, are the changes in the nervous system. Here we find 

 patches of congestion in the brain, and breaking down of the axis 

 cylinders of the nerves. The stomach, in the second place, exhibits 

 haemorrhagic changes, not unlike acute arsenical poisoning. Thirdly, 

 the salivary glands show a degenerative change in a breaking down 

 of their secretory cells. Eoux has pointed out that in life the 

 saliva of a mad dog becomes virulent three days before the appear- 

 ance of the symptoms of disease. The poison appears to be present 

 mainly in the nervous system and the saliva ; it is not present in 

 the blood. 



The method of treatment by inoculation was introduced by 

 Pasteur. Before his time cauterisation of the wound was the only 

 method adopted. But if more than half an hour has elapsed since 

 the bite, cauterisation is of little or no avail. The basis of Pasteur's 

 treatment was the difference in virulence obtainable in spinal cords 



