ORDER ACARINA , 37 



it is absolutely dependent for existence. Generation after 

 generation may occur on the same animal. The mite 

 burrows under the skin, in tliis respect differing from scab 

 mites. 



The adult mites are flattened, rather circular in outline, 

 and may be separated from related forms by the character 

 of the feet and by the presence of six short spines or thorns 

 on the thoracic portion anfl fourteen on the abdominal 

 portion of the body. 



Eggs are deposited along the burrow as the mite extends 

 its channel into the deeper portions of the skin, and as they 

 hatch the young feed upon the surrounding tissues, and it 

 is said moult four times before maturity. When fully grown 

 they wander around and mate on the surface of the skin, 

 after wdiich the females begin a fresh burrow. 



Infection with this parasite is accompanied by intense 

 itching during the formation of pustules and inflamed areas, 

 and while in man it is usually confined to the base of the 

 fingers and between the knuckles, in aggravated cases the 

 whole hand and arm may become invaded. 



The "seven-year itch," "army itch," and "Jackson itch" 

 are simply aggravated cases, where from lack of good sani- 

 tation the mites are able to thrive better than usual. 



In the human subject the application of sulphur ointment, 

 in addition to frequent washing with soap and hot water, 

 and for domestic animals the use of washes and dips, as for 

 scab mites, are to be adopted. 



