24 ANIMAL PAEAS1TES. 



on almost all parts of the body, and not only on the hands, the 

 male organs of generation, and the nipples of women, if we only 

 search for it carefully everywhere. Nevertheless, the hands pre- 

 sent peculiarly favorable conditions for the discovery of the galle- 

 ries, because these become more slwongly marked in consequence 

 of the collection of dirt in their air-holes; and they are also 

 usually more numerous on the hands, and on the organs most fre- 

 quently touched by them, such as the male generative organs, or 

 the female breasts. Nevertheless, there are cases in which, whilst 

 the trunk is covered with passages, the hands are quite free from 

 them ; as is the case, for example, with those who, like painters 

 and lacquerers, soil their hands daily with fats and oils of all 

 kinds. According to Gudden, the hands of such individuals 

 especially remain unattacked, in whom the hands are always cold, 

 as, for instance, in potters, or those who have always wet, cold 

 hands, such as washerwomen. In individuals suffering from 

 habitual cold feet, who can only get warm with difficulty even in 

 bed, the whole body except the feet may be covered with mites. 

 For it is a fact abundantly proved by experience, that the mite 

 becomes more active at all times and in all places when warmed 

 (for instance, in the warm bed, by staying in the sun or at the 

 stove, by dancing, or heating movements or beverages in the 

 winter), but becomes more sluggish in the cold ; so that the 

 patient may diminish the troublesome itching immediately and in 

 a short time by leaving his bed in the winter, if he does not 

 sleep in a heated room. For all these reasons the mites do not 

 like the face, which is usually kept bare even in bed, and exposed 

 to the cold ; but they nevertheless nestle in it perfectly well in little 

 babies, which are completely packed up in bed. Mites were also 

 found in the face of a man who used to sleep upon his left side 

 and draw the bed-clothes carefully up to his chin ; but only in 

 the left cheek which was kept warm. 



At the moment of penetration it gives the mites the greatest trou- 

 ble to pierce through the uppermost horny layer of the epidermis; 

 and this the greater, the thicker, firmer, and coarser the uppermost 

 epidermal layer is. They effect this penetration in a nearly perpen- 

 dicular direction, placing themselves upon their anterior feet, and 

 supporting the body with their long posterior seta3. For the 

 boring in itself they require from ten to thirty minutes. For these 

 reasons the mites in general prefer the delicate, less firm, and 

 thinner spots of the body ; and therefore the space between the 

 fingers, the outside of the hand, the inner surface of the wrist, 



