CHAPTER II. 

 PHTHIRIASIS. 



The term phthiriasis is applied to infestation of the sldn with Hce. 



Causation. Tliese diseases are due to the presence of various para- 

 sites \Yhich live Ijy destroying the epidermic scales, or by piercing the 

 superficial layers of the skin. They are of a greyish-yellow colour, and 

 belong to the genera H(ematopinus and Tricliodcrfes. 



The Hdvnatojiinus forms have pointed heads, and are equipped for 



Fig. 245. — Hceniatopinus cunjsfciinis of Fig. 246. — Hcemaiopinus of the calf, 



the ox, magnified 20 diameters. (After magnified 20 diameters. (After 



Neumann.) Nemnann.) 



penetrating the skin by suction. The Tricliodectcs have a large flat 

 head constructed for masticating. 



The ox harbours two forms of Hcematojnnus and one of Trichodectes, 

 the HieDiatopiuus ciiriistri-nui> and tenuirostriis, and the Tricltodectes 

 soda lis. 



The slieejo suffers from Trklmdcctes sphcrucciilialus and a Mdnpliagus, 



