568 ANNUAL REPORT SMITHSONIAN INSTITUTION, 1921. 



of the United States Department of Agriculture. Dr. Theobald 

 Smith was a young man who had graduated at Cornell University 

 in 1880 and had afterwards taken his degree in medicine at Albany. 

 He had taken special studies which admirably fitted him for this 

 work and became connected with the service at Washington. In 1889 

 he succeeded in discovering a peculiar microorganism in the red 

 blood corpuscles of an infected cow which corresponded in every 

 respect with what one would expect as the true cause of the disease. 

 Doctor Smith was associated at that time with Dr. F. L. Kilborne, 

 who had charge of the field experiment end of this work, and he soon 

 succeeded in showing that the cattle tick was somehow necessary to 

 the transmission of the disease. These observations were fully con- 

 firmed in 1890. In the autumn of that year it was found that when 

 young ticks which had been artificially hatched were placed on 

 cattle there was a sudden astonishing loss of red blood corpuscles 

 which could by no means be explained by the simple abstraction of 

 the blood. Additional experiments showed that the fever was caused 

 by putting recently hatched cattle ticks on susceptible cattle. These 

 results were confirmed in the summers of 1891 and 1892. 



Here again results confirmed an idea current among the people but 

 not indorsed and even derided by scientific men. In 1868 Dr. John 

 Gamgee, who had been brought over from England to study the 

 plague for the United States Government, wrote : 



The tick theory has gained quite a hold during the past summer, but a little 

 thought should have satisfied anyone of the absurdity of this idea. 



The great importance of Smith's work consists in the demonstra- 

 tion that the infection is carried from the adult ticks into the eggs 

 and from them to the young and that they later introduce the virus. 

 The first thing that occurred to the discoverer was that the tick drew 

 out the causative organism from the blood of the cattle and dis- 

 tributed it on the pasture and that the cattle ate it with their food ; 

 but it was not until 1891, when he accidentally found that he could 

 obtain eggs from the ticks in confinement, that it was possible to 

 begin experiments to prove the transmission by the bite. His dis- 

 covery of the causative organism had enabled him to recognize mild 

 cases of the disease produced experimentally, since only by an exami- 

 nation of the blood microscopically and with the blood counter could 

 such a diagnosis be made. 



The remarkable benefits to the people of the United States that 

 have resulted from this discovery are, of course, well known. South- 

 ern cattle after having been " dipped " to free them from ticks can 

 now be carried north beyond the " tick line " without the slightest 

 danger that the southern fever will be transmitted to northern 

 cattle. And. much more than that, the southern country is being 

 rapidly freed from the cattle tick, and by rotation of pasturage and 



