DISEASES OF CATTLE 239 



that the gastric juice has a pronounced deleterious effect upon the 

 virus of rabies. 



Anatomy. If the animals which have succumbed to rabies be 

 examined postmortem, very slight evidence of disease will be found 

 in any of the organs, and, indeed, the absence of any specific lesions 

 may be considered as characteristic. The blood is dark and imper- 

 fectly coagulated. The throat is frequently reddened, and there may 

 be small spots of extravasated blood in the intestines. The stomachs 

 are usually empty. In the spleen there may be hemorrhage en- 

 largements (infarcts). The cadavers rapidly undergo decomposition. 



Differential Diagnosis. It is not an easy matter to decide defin- 

 itely that a given animal has rabies, since the symptoms given above 

 belong in part to a variety of other diseases, among which may be 

 mentioned the excitement seen in young animals following close con- 

 finement, certain vegetable and mineral poisons, acute enteritis, and 

 alterations of the central nervous system in cattle, the most common 

 of which is tuberculosis of the brain and its covering membranes. 

 However, the postmortem lesions should assist in making correct diag- 

 nosis. Tetanus may readily be differentiated from rabies by the per- 

 sistence of muscular cramps, especially of the face and abdomen, 

 which cause these muscles to become set and as hard as wood. In 

 tetanus there is also an absence of a depraved appetite or of a wilful 

 propensity to hurt other animals or to damage the surroundings. 

 The cow remains quiet and the general muscular contraction gives 

 the animal a rigid appearance. There is an absence of paralysis 

 which marks the advanced stage of rabies. The dumb form of rabies 

 in dogs is characterized by the paralysis and pendency of the lower 

 jaw, while in tetanus the jaws are locked. This locking of the jaws 

 in cattle renders the animal incapable of bellowing as in rabies. Fi- 

 nally, tetanus may be distinguished from rabies by the fact that the 

 central nervous system does not contain the infectious principle, 

 while in rabies the inoculation of test rabbits with the brain or cord 

 of a rabid animal will produce the disease with characteristic symp- 

 toms after an interval of fifteen to twenty days. This period of incu- 

 bation is much longer than in tetanus, since the inoculation of rab- 

 bits with tetanus cultures invariably results in death after a short pe- 

 riod and usually within three days. The positive evidence that a 

 rabid dog has been near cattle would greatly assist in making a de- 

 cision in doubtful cases. The disease in dogs is pretty well recog- 

 nized by most people, but in case a suspected dog is killed it is desir- 

 able to open the animal and examine the contents of the stomach. 

 While food is absent, a variety of odd things may be present which 

 the abnormally changed appetite of the rabid dog has induced it to 

 swallow. Among such things may be straws, sticks, glass, rags, earth, 

 pieces of leather, and whatever the animal may have encountered 

 small enough to be swallowed. This miscellaneous collection in the 

 stomach of dogs, together with absence of food, is regarded by 

 authorities as a very valuable sign, and may be made use of by lay- 

 men in case of doubt. In important cases, however, the head of the 

 dog, cow, or other suspected animal should be removed and sent to 



