OP GENERATION. 307 



pagatiou by shoots in the polypi, but a very small portion separates 

 from the stem. But we may first ask, do all these different modes of 

 propagation present themselves in insects ? or, are there generalised 

 observations upon the origin of insects which exclude the one or the 

 other kind of propagation ? Are these observations sufficient to deduce 

 thence a general law, or do they admit of extension to but a very few 

 limited cases ? The investigation of these several questions will con- 

 stitute our first inquiry. 



203. 



With respect to observations upon the equivocal generation of 

 insects, we possess many credible authorities which confirm it. The 

 best known phenomenon of this description is the Phthiriasis, or lousy 

 disease, in which a particular species of louse (Pediculus tabescentium, 

 Alt.* ) originates upon the skin, and collects in great numbers at par- 

 ticular spots, chiefly upon the breast, the back, and the neck, between 

 folds of the skin, making the skin uneven, so that scale-shaped lappets 

 of the epidermis peel off, and beneath which the lice conceal them- 

 selves. We find in ancient, and here and there in modern authors, 

 testimonies of their spontaneous origin, the true cause whereof may 

 consist in a general corruption of the juices in old, weak, and enervated 

 .subjects. Pheretima, according to Herodotus, and Antiochus Epi- 

 phanes, both Herodians, Sylla, Alcmanus, the Emperor Maximian, the 

 poet Ennius, the philosophers Pherecydes and Plato, Philip the Second, 

 and the poet and actor Iftiand, are said to have died of it; and very 

 recently, at Bonn, at the clinical school there, a woman of seventy was 

 found to be thus diseased, but was cured by the rubbing-in of the oil 

 of turpentine. Fourniert relates another instance of it in a cleanly lying- 

 in woman, who had much covered her head, and after suffering head- 

 ache for a fortnight, which totally deprived her of sleep and the desire 

 to eat, a great quantity of lice were found to have originated upon her. 

 A very similar case was observed by my esteemed tutor, P. Kruken- 

 berg, of Halle, in a young girl, who had received a wound in the head, 

 and which was communicated verbally to me. Also, where a pre- 

 disposition exists, the lice appear to be able to originate in the internal 

 cavities; at least, Fournier cites an observation of Marcheli's, upon a 



* Alt., Dissertation de Phtlnriasi. Bonn. 1824, fig. 4. 4to. 

 )- Dirt. Medirale, Art. 



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