1#6 PHTH1RUS INGUINALIS. 



It is almost an established fact that every species of bird, and 

 probably mammiferous animal, has its own peculiar parasite, and 

 many have several. Man affords a nidus and subsistence to three 

 distinct species. Two other species besides the Crab-louse, the 

 Pediculus humamis, of authors, and the Pediculus ccrvicalis, of 

 Latreille, are well known to infest the human body. The latter 

 inhabits the heads of man and upper part of the necks of children, 

 throughout Europe, and is distinguished by its oval lobed cinereous 

 body, marked with an interrupted band on cither side. It deposits 

 single nits or eggs in the hairs of the head, and does not sponta- 

 neously quit the scalp or its natural covering. The latter, which 

 is white and nearly immaculate, seldom appears on the head, but 

 resides on the trunk of the body and on the garments, and is known 

 by the name of the body-louse. The nits are conglomerate, and 

 usually deposited on the folds of linen and other articles of dress. 

 On the continent of Europe, especially in Spain and Portugal, this 

 species is very common. In Britain it is of rare occurrence, and 

 is conjectured to have been introduced from the neighbouring 

 countries. Both these species subsist on the blood of man, which 

 they suck with their proboscis ; but they abound chiefly among 

 the inhabitants of sordid dwellings, or jails and workhouses, and in 

 such situations prey upon all persons indiscriminately. There is, 

 however, a peculiar state of the skin of people advanced in 

 life, and connected with the disease, which has been denominated 

 prurigo senilis by Dr. Willan, in which they are generated not- 

 withstanding every attention to cleanliness, and multiply so rapidly 

 that the patient endures extreme distress from their perpetual irri- 

 tation. It does not appear, from any well ascertained fact, that 

 the species belonging to this genus are ever subcutaneous. Many 

 marvellous stories, indeed, are related by Forrestus, Schenkius, and 

 others, respecting lice bred under the skin, and discharged from 

 abscesses, strumous ulcers, and vesications, and many individuals 

 of great note are said to have died in ancient times from the mul- 

 titude of these pediculi. Thus we are told that among the 

 ancients, Scilla the dictator, Alcmseon the poet, Pherecydes Sirius 

 the philosopher, Callisthenes the Olympian, during the time of 

 his imprisonment, Mutius the lawyer, Eunus the slave, the 



