DIFFERENTIAL DIAGNOSIS 273 



digestive tract may show areas of congestion and ecchymoses. 

 The duration of the disease varies in different species and 

 in different individuals of the same species. In the horse it 

 may last for two or three days only or it may continue for 

 several weeks. In cattle the course is usually less rapid, but 

 it rarely runs longer than two weeks. In sheep it usually 

 terminates fatally within a week and often in two or three 

 days. 



§ 195. Differential diagnosis. Tetanus, while possess- 

 ing quite characteristic symptoms, may be mistaken for a 

 number of other affections or specific diseases. Among those 

 which should receive special attention are cerebro-spinal men- 

 ingitis and rabies (for the symptoms and lesions see those dis- 

 eases), rheumatism, eclampsia, catalepsy, convulsions in the 

 nevvly born and pyemic polyarthritis in lambs and foals. 



The symptoms of tetanus which are perhaps the most 

 diagnostic are (i) the continuous tonic spasms of different 

 groups of muscles, (2) the apparent clearness of mind (if we 

 may attribute such a quality to animals), and (3) the absence 

 of fever in the beginning of the symptoms. The general atti- 

 tude of the animal is also of much value. If the infected 

 wound c^n be found, it is often possible to obtain cover-glass 

 preparations in which the tetanus bacilli can be found. Nega- 

 tive results are in this case not to be considered as final, for it 

 is practically impossible to make these examinations suffi- 

 ciently thorough to be sure of the absence of these bacilli, if 

 they are not found. If they are found the diagnosis may be 

 considered as positive. 



In poisoning with strychnine, there are symptoms which 

 at first may be more confusing. This form of poisoning 

 usually occurs in dogs where tetanus is rare, and again in 

 strychnine poisoning the suddenness of the attack, the rapidity 

 of the course and the increased reflex irritability are valuable 

 diagnostic features. In differentiating tetanus from other 

 afEections in the newly born, the bacteriological examination 

 of cover-glass preparations made from the end of the umbilicus 

 may be of much assistance. 



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