DISEASES OF THE NERVOUS SYSTEM. 153 



brought in contact with the unbroken mucous membrane of the digestive 

 canal, is confirmed by the experiments of Hertwig; at one time he intro- 

 duced the saliva and mucus of a rabid dog into the mouths and throats of 

 healtby animals; again he fed dogs on food with which not only the in- 

 fected saliva and mucus had been mixed, but to which also warm blood 

 taken from rabid animals had been added, all with negative results. He 

 placed healthy dogs in stalls where others affected with rabies had just 

 previously been kept, so that they were brought in frequent contact with 

 the same straw, chains, food, and drinking basins that had been used by 

 the diseased animals, but in no instance was rabies produced; and the 

 same may be said of placing healthy animals in the stall with dogs which 

 had recently died of the disease. 



It is an acknowledged fact, demonstrated by numerous experiments that 

 the milk and flesh of rabid animals ( dogs, sheep, cattle ) may, as a rule be 

 consumed by man and animals without any ill effect. 



The theory that the poison is very rarely communicated in any other 

 way than by the bite of a rabid animal, is fully confirmed by the most 

 wearisome experiments. No instance is as yet known where the virus has 

 been transferred by intermediate vehicles. An ingenious theory has been 

 suggested, thatif minute particles of the poison suffice to propagate infec- 

 tion, possibly certain parasites, fleas, lice, which are nourished by the 

 blood of the dog, and which the more often infest them, may transfer the 

 poison by means of their blood-drawing apparatus, and thus produce 

 inoculation. It is inferred that an analogy exists with other infectious 

 diseases, as for instance small-pox which has been unquestionably trans- 

 ported by flies, and the same is true in cases of malignant pustule. In the 

 latter contagious and very fatal malady, it is believed that flies which 

 have alighted on the ulcers of diseased animals convey the virus, and in- 

 fect other animals and human beings. 



Little or nothing is known as to a predisposition of rabies, it being esti- 

 mated that less than two-thirds of the animals inoculated or bitten are 

 infected by the disease. According to the experiments of some, a rich 

 feeding of the dogs that had been inoculated, favored the outbreak of the 

 disease, while on the other hand it was retarded by poor nourishment. 

 Many dogs have resisted an infection ; in three years Hertwig made nine 

 attempts to inoculate his famous poodle. Some have been known to have 

 been bitten four times by rabid animals and still remain unaffected, as in 

 the case of a dog in the veterinary school at Lyons. 



Symptoms.— The wound from the bite of a rabid animal heals very 

 readily, being but rarely accompanied by inflammation. 



The period of incubation, or development of the disease, is variously 

 estimated by different authors ; in the majority of cases it lasts from three 



