LAVERAN'S DISCOVERY 39 



in conformity with the spirit of investigation of the 

 age. It had already, in the hands of the bacterio- 

 logists, led to the discovery of the anthrax bacillus 

 as the cause of the disease anthrax, the tubercle 

 bacillus as the cause of tuberculosis, the typhoid 

 bacillus as the cause of typhoid fever, the cholera 

 bacillus as the cause of cholera, etc. Considerations 

 like these no doubt stimulated one of Pasteur's dis- 

 ciples to patiently investigate the blood of patients 

 suffering from malaria, for Laveran succeeded in 1880 

 in discovering the parasite in the blood of all cases 

 of malaria. His researches were published in his 

 well-known work " La Paludisme," a work based 

 upon extensive observations made in Algeria. After 

 these observations, which were soon confirmed by dis- 

 tinguished obser\'ers all over the world, there remained 

 no possible doubt that the only cause of the disease 

 known as malarial fever was a microscopic parasite 

 which multiplied in enormous numbers in the blood of 

 the infected patient. Then, as invariably happens, 

 it was soon proved that related organisms could be 

 found in numerous species of animals ; in other words, 

 that this parasite was a widely distributed blood 

 parasite both in the blood of man and animals. 



This discovery was an immense advance. The para- 

 site which caused all the characteristic symptoms was 

 now seen, and for the first time described and classified. 

 But whence did it come ? How did it get into the 

 blood of men ? Did it gain access to the body of 

 man in some finely divided form in miasm or vapours 

 from the marsh ? You will recollect that Dr. Beau- 



