46 DIRECT 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 Ophthalnia. 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.? — Le Jeune, a French physician quoted in Mouffet, describes a 
case, 11 which what seems a different species, since he calls them rather 
large, infested the white of the eye, exciting an intolerable itching. 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, Linné denominates Acarus Lactis. The great author last mentioned 
describes an insect, a native of America, under the name of Pediculus Rici- 
noides, which, upon the authority of Rolander, he informs us gets into the 
feet of people as they walk, sucks their blood, oviposits® 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. Others of the tribe of Acarina, and the insect in 
question amongst the rest, may be similarly circumstanced ; or those that 
Rolander examined might haye been larva, which in this tribe are usually 
hexapods. 
—  Linné appears to have been of opinion that many contagious diseases 
are caused by mites.’ How far he was justified in this opinion I shall not 
here inquire; facts alone can decide the question, and observations made 
1 For further information on this disease, see the valuable Manual of Entomology 
ay Dr. Burmeister, for an English translation of which we are indebted to Mr. 
Shuckard (p.807.), where it is contended, but surely on inconclusive evidence, that 
Pediculus tabescentium, Alt. (Dissertatio de Phthiriasis, Bonne, 1820) is produced by 
spontaneous generation. 
2 On Morbid Poisons, 306, 807. 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 Mém. Aptérologique, 19. 
7 Tnsecta ejusmodi minutissima, forte Acaros divers speciei causas esse diversorum 
morborum contagiosorum, ab analogia et experientia hactenus acquisita, facili 
credimus negotio. Amen, Ac. v.94, 
