DIRECT INJURIES CAUSED BY INSECTS. 67 



As far as the habits of the genus Pediculus, whether in- 

 habiting man or the inferior animals, are at present known, 

 it does not appear, from any well ascertained fact, that the 

 species belonging to it are ever subcutaneous. For this 

 observation, as far as it relates to man, I can produce the 

 highest medical authority. The louse feeds on the surface 

 of the skin," says the learned Dr. Mead in his Medica Sacra ; 

 and Dr. Willan, in his palmary work on Cutaneous Diseases, 

 remarks with respect to the body-louse, that the nits, or 

 eggs, are deposited on the small hairs of the skin," and that 

 the animals are found on the skin, or on the linen, and not 

 under the cuticle, as some authors have represented." And 

 he further observes, that many marvellous stories are 

 related by Forestus, Schenkius, and others, respecting lice 

 bred under the skin, and discharged in swarms from abscesses, 

 strumous ulcers, and vesications. The mode in which Pe- 

 diculi are generated being now so well ascertained, no credit 

 can be given to these accounts." Thus far this great man, 

 who however supposes (in which opinion Dr. Bateman 

 concurs with him) that the authors to whom he alludes had 

 mistaken for lice some other species of insects, which are not 

 unfrequently found in putrefactive sores. 



If these observations be allowed their due weight, it will 

 follow, that a disease produced by animals residing under the 

 cuticle cannot be a true Phthiriasis, and therefore the death 

 of the poet Alcman, and of Pherecydes Syrius the phi- 

 losopher, mentioned by Aristotle, must have been occasioned 

 by some other kind of insect. For, speaking of the lice to 

 which he attributes these catastrophes, he says that " they 

 are produced in the flesh in small pustule-like tumours, 

 which have no pus, and from which when punctured they 

 issue." ^ For the same reason, the disorder which Dr. 

 Heberden has described in his Commentaries, from the com- 

 munications of Sir E. Wilmot, under the name of Morbus 

 pedicularis, must also be a different disease, since, with 

 Aristotle, he likewise represents the insects as inhabiting 

 tumours, from which they may be extracted when opened by 

 a needle. He says, indeed, that in every respect they re- 



1 Hist. Animal. 1, 5. c. 31. 

 F 2 



