346 ANNUAL REPORT SMITHSONIAN INSTITUTION, 1952 



scientists, observed the destruction of the red blood corpuscles of cattle 

 sick with tick fever. In the following year three important discoveries 

 were made in the Bureau of Animal Industry with reference to ticks 

 and tick fever: (1) Smith observed a parasite in the red blood cells of 

 the affected animals (pi. 1, fig. 1) and, on the basis of this discovery, 

 explained the breakdown of the erythrocytes and the various lesions 

 he observed while conducting postmortem examinations of cattle that 

 had succumbed to the disease. (2) While Smith was carrying out 

 these studies, Kilbourne, who was in charge of the modest experiment 

 station aforementioned, started an experiment which ultimately led 

 to the elucidation of the mode of transmission of Texas fever. What 

 Kilbourne did in 1889 is contained in the following statement, written 

 by Smith as part of his contribution to the Sixth and Seventh Annual 

 Reports of the Chief of the Bureau of Animal Industry for the years 

 1889 and 1890 : 



During the summer of 1889 Dr. F. L. Kilbourne in arranging the various en- 

 closures at the experiment station for the exposure of native cattle to the in- 

 fection of Texas fever, conceived the happy idea of testing the popular theory 

 of the relation of ticks to the disease. This he did by placing southern (North 

 Carolina) cattle with native cattle in the same enclosures and picking the ticks 

 from the southern cattle as soon as they had grown large enough to be detected 

 en the skin. This prevented any ticks from maturing and infecting the pasture 

 with the eggs, and hence prevented any ticks from infesting native cattle subse- 

 quently. At the same time in another enclosure the ticks were left on the south- 

 ern cattle. The natives in the latter field died of Texas fever : those in the former 

 did not show any signs of the disease. 



(3) Curtice worked out the life cycle of the fever tick for which he 

 created a new genus, naming it Boophilus, and determined for the first 

 time, in connection with tick life-history studies, that this parasite 

 spent its entire developmental cycle, beginning with the seed tick, on 

 the same host, instead of dropping off the host after each molt. This 

 important discovery made it possible to apply certain measures to con- 

 trol these ticks, and paved the way for tick eradication, which finally 

 resulted in the extermination of bovine piroplasmosis from the United 

 States. 



Additional investigations, carried out jointly by Smith and Kil- 

 bourne between 1890 and 1892, established conclusively that neither 

 the soil from pastures on which ticky cattle had grazed, nor direct 

 physical contact of healthy with affected animals, was involved in the 

 transfer of the disease from parasitized to susceptible cattle. More- 

 over, by placing on susceptible cattle the seed ticks that had hatched 

 from the eggs deposited by gravid female ticks, the symptoms and 

 lesions of tick fever, as well as the causative microparasites, were 

 observed in the animals which became experimentally infected. 

 Finally, it was shown by blood inoculations that the microparasites, 



