BIRD-LICE. 161. 



asis, and add, " that it does not appear, from any -well-ascertainedi. 

 fact, that the species of Pediculi are ever subcutaneous ;" and that,, 

 therefore, the death of the poet Alcman, and of Phresydes Syi'ius^ 

 the philosopher mentioned by Aristotle, must have been occa- 

 sioned by some other kind of insect ; for, when speaking of the 

 lice to vfhich he attributes these catastrophes, he says that they 

 are produced in the flesh in smaU pustule-like tumours, which have 

 no pus, and from which, when punctured, they issue; but, accord- 

 ing to the more recent observations of Alt, published in his Dis- 

 sertatio de Phthtriasi, at Bonn, in 1820, it appears that another 

 species, Pediculm tabescentium, is the real louse of this disease, 

 which, as cited by Burmeister, collect in great numbers upon the 

 skin at particular spots, chiefly upon the breast, the back, and the 

 neck — between folds of the skin, making the surface uneven, so 

 that scale-shaped lappets of the epidermis peel off, beneath which 

 the lice conceal themselves. Of the first appearance of these in- 

 sects much difiiculty exists, both positive and negative evidence 

 being recorded of their non-contagiousness. I cannot, however, 

 adopt the opinion of Burmeister, that they must necessarily be the 

 result of equivocal generation ; and by whom it is supposed that 

 the skin, which has precisely the same structure as the mucous 

 membranes of the intestinal canal, gives rise to parasites peculiar 

 to it. The Pediculis pubis (or Phthirus inguinalis Leach) is a 

 fom-th species ; and, according to Fabricius, the louse of the negro 

 is a fifth distinct species, of a black colour, wdth a large flat head. 

 The pig is also subject to a distinct species {Hcematopinus mis, 

 PI. 1). 



The family Nirmidce (Leach) is composed of the various 

 species of lice found upon birds, to which they are exclu- 

 sively attached, mth the exception of one species, foiuid 

 upon the dog. The mouth is placed on the under side of 

 the head, and composed of two lips and two hooked mandi- 

 bles; the tarsi are distinct, and terminated by two equal- 

 sized hooks; the head is generally large and triangular, 

 semicircular or crescent-shaped, and occasionally with angu- 

 lar projections. The sexes also differ in the size of the head 

 and the antennae. M. Savigny also observed a pair of 

 maxillae with a minute palpus, hidden by the lower lip, 

 which has also a pair of palpi. The body is small and de- 

 pressed, of an oval or elongated form, and often varied with 



p3 



