Diagnosis. 41 



all the horses that contract the worst type of the disease 

 are sure to die with the frequent recurrence of febrile 

 attacks. Horses, which have apparently recovered, are 

 liable to become ill again by certain unsanitary condi- 

 tions, especially by unfavorable climate or hard labor. 

 Such patients usually die of another attack after a few 

 months or in the following year. But in case the course 

 of the disease is good, the patient acquires immunity 

 and febrile fits come no longer. Not only do such 

 patients look healthy (despite the fact that they are 

 still the virus-carriers) but they can stand any ordinary 

 labor. 



VIII. DIAGNOSIS. 



During febrile exacerbation, one can easily diagnose 

 the disease from the symptoms already mentioned. But 

 both in chronic cases with normal temperature and 

 during interfebrile periods, differential diagnosis is ex- 

 tremely difficult, or almost impossible. One has to infer 

 simply from such symptoms as emaciation, alterations 

 of the mucous membrane and a peculiar change in the 

 cardial sounds. In such cases the only sure method of 

 diagnosis is to inoculate the blood of a suspected patient 

 to a healthy horse and to watch the development of 

 typical symptoms in the horse inoculated. 



Diagnosis by serum reaction : — 



1. Complement fixation test. 



a) Experiments using the patient's serum as anti- 

 gen and the immune serum as antibody. 



b) Experiments using aqueous or alcoholic extracts 

 of the patient's bone-marrow, liver, spleen and 

 suprarenal body as antigen and the immune 

 serum as antibody. 



