424 BLOOD DISEASES. 



eggs in from eight to fifteen days ; the ticks which take the 

 longer time lay the larger number of eggs. In hatching these 

 eggs in glass dishes, with damp soil or leaves, the dishes being 

 kept close to prevent the escape of the young brood, it was found 

 that the period of incubation varied according to the surround- 

 ing temperature. When the weather was very hot, the hatching 

 w.is completed in from fifteen to eighteen days. When the 

 season is more advanced, or the temperature lowered, the period 

 of hatching is prolonged to twenty-five, thirty, or even forty days. 



Conclusions. — (1.) Texas cattle fever is a disease of the blood, 

 characterised by a destruction of red corpuscles. The symp- 

 toms are partly due to the anaemia produced, partly to the large 

 amount of cUhris in the blood, which is excreted with difficulty, 

 and which causes derangement of the organs occupied with 

 its removal. 



(2.) The destruction of the red corpuscles is due to a micro- 

 organism or micro-parasite which lives within them. It belongs 

 to the protozoa, and passes through several distinct phases in 

 the blood. 



(3.) Cattle from the permanently infected territory, though 

 otherwise healthy, carry the micro-parasite of Texas fever in 

 their blood. 



(4.) Texas fever may be produced in susceptible cattle by the 

 direct inoculation of blood containing the micro-parasite. 



(o.) Texas fever in nature is transmitted from cattle which 

 come from the permanently infected territory to cattle outside 

 of this territory by the cattle tick (Boojjhilus hovis). 



(6.) The infection is carried by the progeny of the ticks which 

 mature on infected cattle, and is inoculated by them directly 

 into the blood of susceptible cattle. 



(7.) Sick natives may be a source of infection (when ticks are 

 present). 



(8.) Texas fever is more fatal to adult than to young cattle. 



(9.) Two mild attacks or one severe may prevent a subsequent 

 fatal attack. 



(10.) Sheep, rabbits, guinea-pigs, and pigeons are insuscep- 

 tible to direct inoculation. (Other animals have not been tested.) 



(11.) In the diagnosis of Texas fever in the living animal the 

 blood should always be examined microscopically, if possible. 



The regulations of the American Department of Agriculture 

 provide for the prevention of the introduction of the disease into 



