320 



BIOLOGY: GENERAL AND MEDICAL 



very dangerous and destructive malady is 

 transmitted. African relapsing fever is trans- 

 mitted to man by the African tick, Ornitho- 

 dorus moubata, and in the Rocky Mountains a 

 febrile affection, known as bitter root fever, 

 has also been traced to the bites of ticks. 

 The spirillosis of fowls and ducks is spread by 

 the ticks (large lice) that infest them. 

 Of the Mites large numbers frequent plants, 



FIG. 114. Spirochaeta duttoni. Rat blood. X 1500. (After Novy.) 



sucking the juices and causing the leaves to dry 

 and curl. Grain mites, that normally frequent 

 and undoubtedly live upon the stems and hulls 

 of grains seem quite ready to infest man when 

 opportunity offers. Thus an extremely minute 

 mite of this kind, Pediculoides ventricosus, 

 much too small to be seen without the aid of a 

 lens, and commonly found upon straw, some- 

 times renders miserable the lives of those that 



