46 DIKECT INJURIES CAUSED BY INSECTS. 



upon you to believe this ; I shall therefore leave you to act as you please. 

 Thus much for pure Phthiriasis, which term ought to be confined to 

 maladies produced by lice. I shall only further observe, that as many 

 species as exist of these, which are the causes of disease, so many kinds of 

 Phthiriasis will there be. 1 



Acari, or mites, are the next insect sources of disease in the human 

 species, and that not of one, but probably of many kinds, both local and 

 general. They are distinguished from Pediculi not only by their form, but 

 also often by their situation, since they frequently establish themselves 

 under the cuticle. With respect to local disorders, Dr. Adams conjec- 

 tures that Acari may be the cause of certain cases of Ophthalmia. Sir J. 

 Banks, in a letter to that gentleman, relates that some seamen belonging 

 to the Endeavour brig, being tormented with a severe itching round the 

 extremities of the eyelids, one of them was cured by an Otaheitan woman, 

 who with two small splinters of bamboo extracted from between the cilia 

 abundance of very minute lice, which were scarcely visible without a lens, 

 though their motion when laid on the thumb was distinctly perceived. 

 These insects were probably synonymous with the Ciron des paupieres of 

 Sauvages. 2 Le Jeune, a French physician quoted in Mouffet, describes a 

 case, in which what seems a different species, since he calls them rather 

 large, infested the white of the eye, exciting an intolerable itching. 3 Dr. 

 Mead, from the German Ephemerides, gives an account of a woman suck- 

 ling her child, from whose breast proceeded very minute vermicles. 4 These 

 were probably mites, and perhaps that species, which, from its feeding upon 

 milk, Linne denominates Acarus Lactis. The great author last mentioned 

 describes an insect, a native of America, under the name of Pediculus Rid- 

 noides, which, upon the authority of Rolander, he informs us gets into the 

 feet of people as they walk, sucks their blood, oviposits 5 in them, and so 

 occasions very dangerous ulcers. It would be an Acarus, he observes, 

 but it has only six legs. Now Hermann affirms, that some species of 

 Trombidium (a genus separated by Fabricius from Acarus) have in no state 

 more than six legs. 6 Others of the tribe of Acarina, and the insect in 

 question amongst the rest, may be similarly circumstanced ; or those that 

 Rolander examined might have been larvae, which in this tribe are usually 

 hexapods. 



Linne appears to have been of opinion that many contagious diseases 

 are caused by mites. 7 How far he was justified in this opinion I shall not 

 here inquire j facts alone can decide the question, and observations made 



* For further information on this disease, see the valuable Manual of Entomology 

 by Dr. Burmeister, for an English translation of which we are indebted to Mr. 

 Shuckard (p. 307.), where it is contended, but surely on inconclusive evidence, that 

 Pediculus tabescentium, Alt. (Dissertatio de Phthiriasis, Bonnae, 1820) is produced by 

 spontaneous generation. 



2 On Morbid Poisons, 306, 307. 5 Mouffet, 267. 



4 Medica Sacra, 104, 105. 



5 It is to be hoped this new word may be admitted, as the laying of eggs cannot 

 otherwise be expressed without a periphrasis, for the same reason its substantive 

 Oviposition will be employed. 



6 Mem. Apterologique, 19. 



7 Insecta ejusmodi minutissima, forte Acaros diversae speciei causas esse diversorum 

 morborum contagiosorum, ab analogia et experientia hactenus acquisita, facili 

 credimus negotio. Amain. Ac. v. 94, 



