190 PHTHIRUS INGUINALIS. 



insects. A decoction of the seeds of stavesacre, of black pepper, 

 kindly accompanied me to the House of Industry there, to examine 

 a patient whose body was very full of the pustules of this disorder ; 

 but though we used a good magnifier, we could discover nothing 

 like an insect. I must observe, however, that our examination 

 was made in December, in severe weather, when the cold might 

 perhaps render the animal torpid, and less easy to be discovered. 



" From the above facts it seems fair to infer that this animal is 

 not invariably the cause of scabies, but that there arc cases with 

 which it has no connexion. Now, from this inference, would not 

 another also follow, that the disease produced by the insect is 

 specifically distinct from that in which it cannot be found? Sau- 

 vages and Dr. Adams are both of this opinion, the former assign- 

 ing it to the trivial name of vermicularis ; and the latter proving, 

 by very satisfactory arguments, that it is different from the other. 

 If they were both animate diseases, but derived from two distinct 

 species of animals, (for it seems not impossible that even our 

 common itch may be caused by a bite more minute than the other, 

 and so more difficult to find), they would properly be considered as 

 distinct species ; much more, therefore, if one be animate and the 

 other inanimate. Nay this, I should think, would lead to a doubt 

 whether even their genus were the same. I shall dismiss this 

 part of my subject with the mention of a discovery of Dr. Adams, 

 which seems to have escaped both Linne and De Geer — that the 

 Acarus Scabiei is endowed with the faculty of leaping ; (in this 

 respect resembling the insect found by Willan in Prurigo senilis,) 

 for which purpose its four posterior thighs are incrassated.* 



" I shall now produce two instances where mites were evidently 

 concerned. Dr. Mead, from the German Ephejneridcs, relates 

 the miserable case of a French nobleman, from whose eyes, nostrils, 

 mouth, and urinary passage, animalcules of a red colour, and ex- 

 cessively minute, broke forth day and night, attended by the most 

 horrible and excruciating pains, and at length occasioned his 

 death. The account further says, that they were produced from 



* It maybe mentioned here as a remarkable fact, that the Acarus Scabiei was 

 discovered by M. Latreille upon a New Holland quadruped {Phascolomys fusea, 

 Geoffr.) of the Marsupian tribe. A T . Diet. tfHisi. Nat.x\'\. 222. 



