Protozoan Cattle Fever. Texas Fever. Paludism of Cattle. 549 



in a field September 14th and 15th. The new generation of ticks 

 was retarded by the cool season, so that few larvae appeared on 

 the native stock yet one of the three sickened. 



These results were confirmed by a series of other similar ex- 

 periments. 



In a further experiment, September 13th, thousands of ticks, 

 mostly mature, from North Carolina, were scattered over a sound 

 lot and four native cattle turned into it next day. Three sickened 

 and one, to outward appearance, escaped. 



These results were corroborated by experiments made in suc- 

 ceeding years. In addition the disease was produced regularly 

 in native stock by placing on their skin the six-legged larvae of 

 boophilus bovis, which had been hatched in glass vessels in the 

 laboratory. It was also shown that the Washington winter de- 

 stroyed the ticks in infected pastures so that native cattle could 

 be safely turned on them the following spring or summer. 



To summarize : — 



1. The blood of southern cattle containing the piroplasma pro- 

 duced the disease wheu injected into a healthy susceptible ani- 

 mal. 



2. The animal with piroplasma in its blood, did not convey the 

 disease, in the absence of ticks, to a susceptible animal kept with 

 it. 



3. The animal with piroplasma in its blood and covered with 

 ticks conveyed the disease to a susceptible animal kept with it. 



4. The ticks hatched and raised in glass vessels in the labora- 

 tory, when put on susceptible animals, infected them. 



5. Ticks taken from cattle harboring the piroplasma, and put 

 on the skin of susceptible animals, or on their pastures in the 

 warm season, infected the exposed stock. 



6. The six-legged larvae developed in the laboratory from the 

 eggs of mature ticks, taken from cattle having the piroplasma, 

 conveyed the disease. 



7. On bare pastures as far south as Washington the winter 

 frosts destroyed the ticks so as to render the pastures safe on the 

 following season. 



8. Ticks artificially raised in a warm laboratory, produced the 

 disease when placed on susceptible cattle in a warmed stable 

 (65 to 8o° F.) in winter. 



