Differential Diagnosis. 485 



resulting from dislocation of the inferior maxilla, the mouth 

 is continuously open, while in rabies the jaw moves slightly up 

 and. down but only in limited degree. Finally a trigeminal or 

 facial paralysis sometimes develops independently or in the 

 course of distemper; however, in such cases the total absence 

 of other symptoms of paralysis, especially in the hind limbs, is 

 against rabies. 



In cats, dogs, and cattle, perhaps also in other animals, 

 rabies is easily confounded with paralysis bulbaris infectiosa, 

 which disease is to be considered especially when the animals 

 rub and gnaw at the place of the bite (see p. 496). 



Finally, owing to confinement of hitherto free animals, to 

 the lack of opportunity for copulation, nymphomania and saty- 

 riasis, removal of the young from their dams, as well as in 

 many acute infectious diseases, attacks of frenzy may occur, but 

 they may be readily distinguished from rabies by proper obser- 

 vation of the accompanying conditions, particularly the absence 

 of paralytic symptoms. 



As to the post-mortem diagnosis, the absence of normal food 

 and the presence of foreign bodies in the stomach form the 

 only finding that is in any way characteristic, but even 

 this does not afford any real proof, because, in exceptional 

 cases, foreign liodies are also found in the stomachs of dogs 

 not suffering from rabies, especially in young dogs and in those 

 with digestive troubles (in the latter the bodies are usually 

 found with normal food). On the other hand, the presence 

 of food substances in the stomach does not by any means exclude 

 the possibility of rabies. The presence of sugar in the urine 

 strongly supports the diagnosis of rabies, but even this does 

 not constitute a full proof, because sugar is also found in the 

 urine in other diseases. The difficulty of diagnosis is enhanced 

 by the fact that many rabid animals are killed before the com- 

 plete development of the symptoms, so that even partially char- 

 acteristic changes have no time to develop. 



The existence of rabies is established definitely by animal 

 experiments and also by microscopical examination of the brain, 

 at least if the results are positive. 



Complement fixation with nerve substance as antigen, has not yet succeeded in 

 showing the presence of the complement fixing amboceptors in the serum of immunized 

 or rabid animals (Centanni, Heller & Tomarkin, Friedberger). 



Microscopical Diagnosis. In this connection the detection of Negri 

 bodies has a very high diagnostic value, while the examination of the 

 nerve ganglia gives less certain results. 



1. Detection of Negri Bodies. The numerous experiments follow- 

 ing the discovery of these formations (see p. 465) have shown uni- 

 formly that they are only present in animals or human beings suffering 

 from rabies, and that, through their detection, the diagnosis of rabies 

 may be definitely established. On the other hand, they may not be 

 present in the initial stage of the disease, and rabid animals are often 

 killed shortly after the affection develops ; therefore the negative result 



