Protozoan Cattle Fever. Texas Fever. Paludism of Cattle. 593 



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, aud 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 80° F.) in winter. 



9. In the Gulf states, in stables which the cattle occupy con- 

 stantly or enter twice daily for milking or feeding, the ticks may 

 live through the entire winter. The same has occurred in the 

 warm swill stables in the north. 



ID. When taken into a new locality, it is rarely the mature 

 ovigerous ticks that bite and infect the native cattle of the place, 

 but the next generation of larvas, so that time must be allowed 

 for the laying and hatching of ova. 



1 1 . Ovipositing usually occupies about a week, while hatching 

 varies with the temperature from two to six weeks. 



12. Cases can be adduced in which native cattle followed, on 

 the same pasture, the tick-bearing infecting cattle, and remained 

 for a week or more, and yet escaped, the larvse being as yet un- 

 hatched from the ova. Other native cattle, following these two 

 or three weeks later, perished almost without exception. 



13. This delay in the hatching may be indefinitely prolonged, 

 and thus in the southern states, the winter may be tided over, 

 without the loss of vitality in the ova", especially if it is covered 

 by leaves, moss, wood, or decaying vegetable matter. 



14. When dealing with liing plague in Chicago in 1888, I 

 noted the facts that every cow that entered a city stable through 



38 



