634 APPENDIX. 



With regard to immunity, we know that one attack 

 of malaria may linger a long time, and seems rather to 

 favor than to prevent a new infection. There is, 

 however, a natural susceptibility to the disease which 

 is very variable. Different races of men especially 

 seem to possess in variable degree the power of resist- 

 ance to malarial infection. This is shown not only in 

 a diminished tendency to contract the disease, but also 

 in the form by which they are affected. For instance, 

 the negroes in the Southern parts of the United States 

 are much less liable to contract malaria than the whites; 

 and Martin reports that the Europeans living in Suma- 

 tra are far more frequently and severely affected by 

 malaria than the natives, who, if they are attacked at 

 all, it is only with the simple intermittent tertian and 

 quartan fevers. 



The Action of Quinine on the Parasites. Laveran 

 showed that a solution of 1 to 10,000 of quinine, run 

 under the cover-glass, would check at once the move- 

 ments of malarial organisms. As demonstrated by 

 Marchiafava and Celli, however, a like effect is pro- 

 duced either by the water or by the salt solution in 

 which the quinine is dissolved, and we meet with an 

 almost insuperable difficulty in the study of the direct 

 action of the drug upon the parasites themselves. 



Many careful experiments have been made to deter- 

 mine the effect of quinine on the parasites circulating 

 in the blood, and Romanowsky, Golgi and others have 

 reported a diminution in the activity of the amoeboid 

 movements. Osier stated that, as a result of careful 

 hourly examinations made in a series of cases with a 

 view of ascertaining the direct influence of full doses of 

 quinine, he was unable to make up his mind that any 



