Protozoan Cattle Fever. Texas Fever. Paludism of Cattle. 567 



with the northern cattle on more than equal terms. Living in 

 the open air, they would in the main escape tuberculosis and the 

 other stable-propagated diseases of the north, and their dairy and 

 beef products would enter the market free from suspicion, and 

 command a readier sale, if not a higher price. The stock them- 

 selves could be moved to northern markets at all seasons without 

 restriction, and escape the serious losses that now come from a 

 sudden transfer, while pyroplasma-infected and susceptible, to the 

 violent excitement of travel, and the frost-bound destination. 

 Their owners could watch the markets and sell in the best, in 

 place of being compelled, as at present, to hurry them in during 

 November and December, and to sell often at a ruinous sacrifice. 

 With the extinction of the boophilus the present unrestricted 

 pasturage and all other privileges now enjoyed would return, 

 freighted with a value never borne before, and the few Southern 

 cattle and cattle products need fear no competition in the markets 

 of the world, and could no longer be justly subjected to any 

 restriction. 



There would remain the constant danger of the introduction of 

 the boophilus anew from Mexico, the West Indian Islands and 

 the Central and South American States, where in the absence of 

 frosts the boophilus cannot be extirpated in the same way, and 

 here accordingly all importation must be forbidden. Cattle from 

 Southern Florida and from islands on our Southern Coast may 

 demand a similar exclusion. There is too much at stake to per- 

 mit any laxity, and no infected area should be allowed to send 

 out its cattle until it has been abundantly well proved that such 

 district or State is absolutely tick-free. 



2d. Immunization : Encreasing the Resistance to the Piroplasma 

 Bigeminum. That cattle can be fortified to resist the attacks of 

 the piroplasma is shown in the immunity possessed by the in- 

 digenous herds generally, in the regions infested with this para- 

 site and the boophilus. To begin with, there may be a survival 

 of the fittest, the more susceptible strains of blood having been 

 long ago cut off. But the immune southern cattle if kept for 

 years outside of the infested area and then returned to it, suffer a 

 mortality about as great as that of northern cattle in the same 

 circumstances. Their earlier immunity, therefore, is not merely 

 a racial difference, but must be due in greatest part to an acquired 



