22 STRONG AND TEAGUE. 



I. SERUM THERAPY AND VACCINATION. 



Antibodies against trypanosomata have been demonstrated in the 

 sera of animals suffering from a chronic form of the disease and it has 

 even been shown that such sera when injected simultaneously with the 

 tiypanosomata of nagana into rats will sometimes protect the latter from 

 infection. However, all attempts to obtain a therapeutic serum against 

 the trypanosoma infections have thus far failed. Laveran and Mesnil 

 (1902) tested the effect of injecting human serum into nagana-infected 

 rats and mice on the supposition that man is not susceptible to nagana. 

 It is claimed that marked improvement followed the injection of human 

 serum. However, the disease in these animals was not cured. 



The vaccine treatment, that is, the injection of blood containing 

 killed trypanosomata, seems likewise to have no influence on the course 

 of the disease. 



Martini suggested that the inoculation of cattle and horses in infected 

 districts with an avirulent strain of the trypanosoma in question might 

 protect them against later infection with a more virulent form of the 

 disease. In our opinion this would be a very dangerous experiment; 

 for it seems possible that the avirulent trypanosomata might regain 

 their virulence in the course of time and that the "parasite carriers" for 

 which we were responsible might become a fearful menace to all the 

 stock of the district. In this connection it is interesting to note that 

 a number of observers have shown that animals which have recovered 

 from trypanosomiasis by treatment are not immune on reinoculation. 

 Manteufel also found that a previous combined treatment with virulent 

 trypanosomata and a highly immune specific serum does not as a rule 

 result in the production of an efficient immunity. 



TREATMENT BY DRUGS. 



In observing the results of any form of treatment, usually the more 

 acute the course of the disease, the more readily can conclusions be 

 formed in regard to the efficacy of any particular drug. This fact 

 should be borne in mind in the selection of the experimental animals for 

 testing the various remedies. The extremely chronic character of sleep- 

 ing sickness in man explains why such a long time has elapsed before 

 anything like a unanimity of opinion with regard to the efficacy or 

 inefficacy of certain drugs has been achieved. 



Since small animals very generally tolerate larger doses of medicine 

 in proportion to their body weights than do larger ones, theoretically it 

 should be easier to destroy parasites in the blood of the former than of 

 the latter. It will be seen later in the discussion that this actually has 

 been found to be the ease. It therefore follows, and should be borne in 

 mind in the following discussion of the literature, that results obtained on 

 the smaller animals with a given drag can not also be assumed to hold 

 good for larger ones. 



