206 JAMES CARROLL. 



blood. He encountered most serious difficulties before he could 

 achieve his end, but it was finally accomplished, and without 

 it the yellow fever experiments would undoubtedly have been 

 far less useful to mankind. The points which were established 

 by Carroll's individual efforts during this visit are : 



1. That the specific agent of yellow fever is present in the 

 blood during at least the first, second, and third days of the 

 disease. 



2. That the specific agent is destroyed, or at any rate attenu- 

 ated by heating up to 55° C. for ten minutes. 



3. That yellow fever can be produced by the injection of a 

 small quantity of diluted serum taken directly from a patient 

 and passed through a Berkefeld filter. 



4. That, as the specific agent is capable of passing through 

 a Berkefeld filter, it must belong to the class of organisms known 

 as ultra-microscopic. 



Yellow fever was not the only disease which Carroll em- 

 ployed his knowledge of bacteriology to investigate. In 1898 

 he was sent to Camp Alger to study the blood of the fever 

 patients there and it was he who first showed that the illness 

 prevailing among the troops there was typhoid fever and not 

 malaria. On several other occasions he was employed to inves- 

 tigate typhoid fever. 



After his return to the United States in 1901, Carroll continued 

 to disseminate the valuable knowledge which he had acquired 

 on the subject of yellow fever through the medium of the medi- 

 cal press. The first paper which he published independently, 

 on "The Treatment of Yellow Fever," is the first contribution 

 to the therapeutics of the disease after its mode of transmission 

 became known ; his last is the section on yellow fever in the 

 second volume of Osier's " System of Medicine." 



For some years Carroll's services received no official recog- 

 nition, but during the last year of his life honors began to come to 

 him in which he took a manly and justifiable pleasure. He was 

 promoted from the rank of Lieutenant to that of Major, and two 

 universities, the University of Nebraska and the University of 

 Maryland, conferred upon him the honorary degree of LL.D. 

 In the summer of 1907 the heart lesion, which originated in his 



