ITCH MITES. 311 



CASE This horse, with the view of seeing the so-called scab mite (Acarus 

 exulcerans), was exposed to the sun. The scab on the hide was 

 loosened with our hands, and we took a magnifying glass to exa- 

 mine the scab with, but saw no scab mites. Then we took some 

 of the scab and laid it on white paper, and searched amongst it 

 again with the magnifying glass without seeing what we wished, 

 but instead, five days after the examination, we had scab pustules 

 on both hands. That we could not have got them in any other 

 way was certain, and a proof was, that five veterinary surgeons 

 besides ourselves were attacked from the same horse." 



In both of these cases (the latter more especially, for the itch 

 pustules are mentioned) the mites burrowed in the skin of the 

 horse. The way in which the Psoroptes equi proceeds is quite 

 different. As already said, the mandibles are not adapted for 

 burrowing, but for lancing — and accordingly it makes no burrow. 

 It lays its eggs on the skin to which they adhere by a gluey matter. 

 The mites themselves move about among the hairs, often crowded 

 in great numbers, and they feed by plunging their sharp mandibles 

 deep into the skin, and sucking out its juice, although they do not 

 and cannot penetrate so deep as to pass through the skin or reach 

 the blood. It is thus easy to say whether an itch infection is that 

 of the man or the horse mite. Indeed, from experiments made, 

 the horse mite does not seem capable of establishing itself 

 on man. Specimens have been transplanted on to him, and 

 all that he has felt has been a slight uneasiness from the mites 

 plunging their mandibles into the skin ; but that soon passed : 

 the mites went their way and disappeared, and no itch complaint 

 followed. 



On the sheep it is said by M. Delafond to give rise to the 

 disease called " black muzzle." The sheep attacked has the skin 

 of the face, lips, around the eyes, and the external surface of the 

 ears covered with a great quantity of furrows and mangy papillae 

 forming thick hard adherent greyish crusts under which the mites 

 live and breed, and the fleece falls off in great flakes. 



