162 GEKLACH ON THE ITCH AND MANGE. 



the scales are laid with their under surface uppermost on the 

 arm. In the course of twelve hours they pass from the 

 scales on the arm and burrow into the skin at the part 

 covered by the scab. On removing the latter, the parasite 

 is seen as a white spot on a somewhat reddened skin, or 

 upon the small red papula. With the point of a needle the 

 white summit of the epidermic vesicle is punctured, and the 

 sarcoptes is obtained. If the inflammatory nodule be allowed 

 to pass to the state of a bladder, then the mite is rarely 

 found. If there be only a few of the acari on the scales 

 applied to the arm, the red points or nodules are only seen 

 next day, and before the appearance of this eruption the 

 insects are not, as a rule, to be found on the skin ; if many 

 of the parasites exist on the scales, then in the course of a 

 few hours they may be obtained on the arm. 



The dermatodectes, especially of cattle and horses, are very 

 readily found in a similar way. Sometimes the scales need 

 only be on the human skin one hour. 



The symbiotes are not discovered by this procedure, but 

 they are readily obtained from beneath the scales, by laying 

 the latter on a paper in the sun, where next day they are 

 found in small clusters. 



When sarcoptes are sought by placing scabs on the skin 

 of the arm, lest any should have remained behind, the skin 

 should be rubbed with a little turpentine oil or some oatmeal. 

 With the other forms of parasites mentioned this precaution 

 is unnecessary. 



Gerlach's descriptions of the itch insects are excellent. With 

 reference to the scarcity of male in comparison to the num- 

 ber of female acari to be found in cases of itch, he believes 

 that though there is, no doubt, a majority of females, never- 

 theless the males, in a great measure, elude detection. They 

 are small, and very active, burrowing only in short grooves, 



