RABIES. 459 



guinea-pigs or rabbits. This antitoxin is possibly secreted by special 

 glands, such as the thymus and thyroid ; and, according to Brieger 

 and others, extracts of the thymus gland are antitoxic to other 

 toxins, as well as the tetanus toxin. 



These experiments have resulted in the employment of tetanus 

 antitoxin as a therapeutic agent (p. 63). 



RABIES. 



Rabies, or hydrophobia, is a disease like tetanus, the symptoms 

 being produced by a virus acting upon the nervous system. The 

 specific virus appears to originate in dogs, wolves, and jackals ; and 

 by wounds inflicted by rabid animals, or by inoculation, the disease 

 may be communicated to man, cattle, sheep, deer, cats, rabbits, and 

 swine. 



Among the early symptoms observed in the dog are sulkiness 

 and restlessness, depraved appetite, and irritability. A peculiar 

 expression of the countenance may be noticed, with twitchings of the 

 eyes and face, and the animal's attention appears to be fixed upon 

 some imaginary object. 'A rabid dog is constantly trying to drink, 

 and at times howls or barks in a peculiar tone, whilst the breathing 

 becomes very irregular. On the fourth day, or later, death follows. 

 After death the glands are enlarged and congested, the tonsils are 

 inflamed, and the vessels of the epiglottis injected. In some cases 

 there is inflammation of the lungs, and the stomach may contain a 

 mass of straw, hair, and horse-dung. The membranes of the brain 

 and the spinal cord may be also congested. All these symptoms 

 may be present, or some only, or they may be .entirely absent ; and 

 it is partly for this reason that Pasteur's researches have been of 

 such enormous value. Very little was known of the experimental 

 production of rabies until Pasteur commenced his investigations ; and 

 the test, which can be applied by inoculating rabbits, is invaluable 

 as a means of diagnosing rabies with absolute certainty. Dogs 

 suffer from symptoms simulating those of rabies ; and formerly, when 

 human beings were bitten, it was impossible in some cases to 

 determine whether the dog had been suffering from rabies or not. 

 We are indebted to Pasteur for the only reliable test which can 

 be applied ; and we are now in a position, when a human being is 

 bitten by a dog supposed to be, but not really, rabid, to remove 

 all cause for the anxiety which would otherwise remain for months 

 and even years. 



In man the period of incubation lasts from eight days to 



