DISEASES OF CATTLE 325 



tick within a week molts, and the second or nymphal stage of the 

 parasite's life is thus ushered in. After this change it has four pairs 

 of legs. Within another week another molt takes place by which 

 the tick passes from the nymphal to the sexual, or adult, stage. Im- 

 pregnation now takes place, and, with the development of the ova in 

 the body, the animal takes an increased quantity of blood, so that it 

 becomes very much larger in a few days. That the rapid growth is 

 due to the blood taken in may be easily proved by crushing one. 

 The intestine is distended with a thick, tarry mass composed of 

 partly digested blood. When the female has reached a certain stage 

 of maturity she drops to the ground and 'begins to lay a large number 

 of eggs, which hatch in the time given above. 



The life of the cattle tick is thus spent largely on cattle, and 

 although the young, or larvae, may live for a long time on the ground 

 in the summer season, they can not mature excepting as parasites on 

 cattle and horses. We have purposely omitted various details of the 

 life history, including that of the male, as they are not necessary to 

 an understanding of our present subject Texas fever. How this is 

 transmitted we will proceed to consider. 



Southern cattle sent North during the spring and summer 

 months carry on their bodies large numbers of the cattle tick. These 

 when matured drop off and lay their eggs on Northern pastures. 

 These hatch, and the young tick soon gets upon any Northern cattle 

 which happen to be on the pasture. As soon as they have attached 

 themselves to the skin they inoculate the cattle, and Texas fever 

 breaks out a week or more thereafter. For many years there had 

 been a growing suspicion that the cattle tick was in some way con- 

 cerned in the spread of Texas fever, and the facts which supported this 

 supposition finally became so numerous and convincing that a series 

 of experiments were inaugurated by the Bureau of Animal Industry 

 which served to show that the tick was abundantly able to carry the 

 disease to a herd of healthy cattle, and in fact was probably the only 

 agent concerned in the transmission of the disease from Southern 

 cattle to susceptible Northern animals. 



The regulations which have been enacted by the Department of 

 Agriculture for the control of cattle shipments from the infected dis- 

 tricts have for their initial purpose the prevention of the transporta- 

 tion of cattle ticks from infected regions to those that are nonin- 

 fected, either upon cattle or in stock cars or other conveyer, and the 

 exclusion of these parasites from noninfected territory has in every 

 instance been found a certain method of excluding Texas fever. 



INJURIOUS EFFECTS OF CATTLE TICKS. 



Many cattle owners who have always been accustomed to see 

 both ticks and ticky cattle on their farms are unfortunately not in- 

 clined to attach much importance to cattle ticks, and, as a rule, 

 through lack of appreciation of their damaging effects, placidly con- 

 sider them as of little consequence. That ticks may be detrimental 

 to their hosts in several ways has probably not suggested itself to 

 these stockmen, who are most vitally affected, and it therefore seems 

 necessary to emphasize the fact that, in addition to their relation to 



