318 EXPERIMENT STATION RECORD. 



cattle business in the Southern States. The tremendous losses 

 incurred as the result of attempts at traffic in cattle between the North 

 and South brought the matter prominently before the Federal Govern- 

 ment in 1868, after which Dr. Curtice and others, under the direction 

 of Dr. D. E. Salmon, carried on investigations regarding the nature 

 of the disease and practical means of controlling it. 



After a long series of experiments by the Bureau of Animal Indus- 

 try, Drs. Smith and Kilborne demonstrated, in 1893, that the disease 

 is transmitted from one animal to another by means of the cattle 

 tick. It was also shown that susceptible cattle could be rendered 

 immune to the disease by inoculating them with the blood of other 

 cattle which had recovered from the disease. The elaboration of this 

 method by the Missouri and Texas stations and others rendered it pos- 

 sible for northern breeders of blooded stock to immunize the animals 

 which they wished to ship south, and thus avoid the serious losses which 

 the} T would otherwise suffer. 



Promising as this method has become, it has long been apparent 

 that objections attach to it. In the first place, the immunity thus 

 produced is not absolute. In some portions of the quarantined area 

 native animals immunized by gradual tick infestation from early calf- 

 hood may subsequently succumb to Texas fever as a result of excessive 

 infestation with ticks, or from infestation with unusually virulent 

 ticks. Moreover, the method of immunization is not a permanent 

 remedy for Texas fever, but requires a continual outlay and treatment 

 for all susceptible animals, including native southern cattle on tick- 

 free pastures as well as cattle north of the quarantine line intended for 

 shipment into the South. 



Obviously, the most perfect system of immunization does not remove 

 the quarantine line, or permit the transportation of cattle from the 

 Southern States to the northern markets without the inconveniences 

 and restrictions which are required in dealing with such cattle. On 

 account of this inadequac} 7 , a number of investigators have for several 

 years been working along another line of attack which gives hope of 

 ultimate success. Drs. Cooper Curtice, Tait Butler, Prof. H. A. 

 Morgan, and other investigators have demonstrated that by a simple 

 method of pasture rotation, ticks ma} T be eradicated from infected 

 pastures within a single year. During the past four years Dr. Butler 

 has practically eradicated ticks from twelve counties in North Carolina 

 at a total cost of $15,000, and in this time not a single case of reinfes- 

 tation in the area of operation has occurred. 



The method of eradication is based upon known facts concerning the 

 life history of the cattle tick, without the agency of which Texas fever 

 can not be transmitted. The engorged cattle tick drops to the ground 

 from infested cattle, la}s its ^gg^, which hatch into young so-called 

 seed ticks, and these remain upon the grass until opportunity is offered 

 to attach themselves to cattle. After attachment they remain upon 



