688 MICROBIOLOGY OF THE DISEASES OF MAN AND ANIMALS. 



ticks which have dropped to the ground. In the United States, cattle 

 on some farms are kept free from ticks, and consequently from red 

 water, by a manoeuvre which takes advantage of the way in which the 

 tick transmits the disease. The adult tick remains upon her host until 

 she is ready to deposit her eggs; she then drops off, lays her eggs and 

 dies. The young ticks, hatched from these eggs, attach themselves to 

 new hosts; and it is through their bites that the disease is transmitted. 

 Therefore, since the disease is transmitted by the progeny of ticks which 

 have fed upon infected mammals, susceptible cattle may be protected 

 from the disease by preventing young ticks from reaching them. This 

 may be done by not allowing them to feed over fields where ticks may 

 have been dropped until sufficient time, about ten months, has elapsed 

 for all the ticks and their progeny to have died of starvation. 



SARCOSPORIDIA. 



Different species of this order are frequent parasites of all the domestic 

 animals, of mice and, occasionally, of man. Mice are killed by them and it is 

 possible that they may produce ill effects in men and domestic animals; but 

 no definite illness is associated with their presence. Though they may occur 

 in any part of the body, they are most numerous in muscles, such as those of the 

 larynx and oesophagus, which are near the alimentary canal. For this reason 

 it seems possible that they may enter the bodies of their hosts with food; but 

 nothing is known with certainty of their life history. 



MYXOSPORIDIA. 



One member of this order, Myxobolus pfeifferi, is mentioned as a type of 

 the parasites which are parasitic beneath the skin of fishes and produce diseases 

 characterized by the presence of boil-like lesions. 



MICROSPORIDIA. 



Protozoa belonging to this order do not produce disease in man. They 

 are the cause of a disease of bees, and they are of particular interest because one 

 of them, Nosema bombycis, causes Pe"brine. 



PEBRINE. 

 Nosema bombycis. 



This is a disease of the silk worm; it was the first disease proved to be 

 due to an infection by a microscopical parasite. At the middle of the 



