MOSQUITOES 



73 



ing houses of the United States. If this worm is found in 



these carcasses, they are condemned and burned because 



it is by eating them that human beings get the Trichina 



in their bodies, which may cause death. Many more 



examples might be given of parasites 



that live in more than one host. So, 



after all, the fact that the malarial 



germ lives in both man and mosquitoes 



is not a new and anomalous discovery, 



having no parallel in animal life, for 



many similar examples have been long 



and well known. The nearest parallel 



we have is the germ causing what is 



known as Texas fever or tick fever, in 



the cattle of the Southern States. 



The parasite causing this disease is 



very similar to the human malarial 



parasite and acts on the blood of 



cattle in a similar way, namely, by 



destroying the red blood corpuscles. 



It causes fever and chills in the cattle 



quite similar to those caused in man 



by the malarial parasite. In fact, many writers call 



Texas fever Cattle Malaria. This germ spends one part 



of its existence in the common cattle tick and the other 



part in the blood of cattle. The germ is conveyed from 



one animal to another and injected into the blood by the 



bite of the tick very similar to the manner in which the 



malarial germ is carried to a person and injected into the 



blood by a mosquito. It has been demonstrated again 



and again that if cattle be kept free from ticks, they will 



not have Texas fever. On the other hand, it has been 



Fig. 29. — Trichinella 

 spiralis embedded 

 in human muscle, 

 much enlarged. 



