OF GENERATION. 309 



ings, out of which they came when opened. These creatures were 

 doubtlessly no lice, but Acarinte, for wherever insects have been found 

 in pustules or vesicles beneath the epidermis, they belonged to this 

 family, and not to the true lice. Many instances of this kind occur, 

 and are generally known, at least to physicians ; for such are the Acari 

 of the itch (Sarcoptis scabiei, and Acarus exulcerans), which are 

 found in the immature pustules of that disease, and which will produce 

 it in healthy individuals when placed upon them. But as we exclude 

 the Acari from the class of insects, we can take no further notice of 

 those several cases nor of the species producing them ; we consequently 

 refer to the article Acarina and Acarus in the Allgem. Encyclopedie 

 of Ersch and Gruber, torn i., which are written by Nitzsch, doubt- 

 lessly the best acquainted of anybody with parasitic insects and the 

 Arachnidce. 



The Acari stand in the same degree of relation to the Arachnides 

 that the lice do to insects, and consequently the similar mode of living 

 of 'both families will not strike us as strange, but rather demonstra- 

 tively ; if the one originate spontaneously, so will the other : of the 

 Acari it is certain, and consequently also of the lice, even although 

 direct observations are wanting. 



But we may ask, Whence originates the first louse in Phthiriasis ? 

 Does it proceed from the skin as a deus ex machina ? or are certain 

 parts of man developed to insects ? or are they formed from substances 

 merely deposited upon the skin ? 



With respect to the first opinion, it admits neither of being compre- 

 hended nor supported by argument, and must therefore be wholly 

 rejected. For the transformation of lappets of the skin into lice, we 

 might cite as analogous the supposed transformation of intestinal nocks 

 into intestinal worms; but these have at least vessels, and participate 

 in the vitality of the organism, which, in the dead lappets of the skin 

 which peel off, is no longer the case, for it is impossible that such 

 should be transformed to living beings ; therefore the third is the only 

 tenable opinion, and this we adopt. From the perspiration ivhich accu- 

 mulates chiefly at the above-named parts of the body, namely, at the head, 

 neck, breast, along the back, beneath the arm-pits, and the softer parts, 

 the germs of new organisms are developed in such individuals whose 

 secretions have a strong tendency to corruption, and this is precisely 

 the case in children and diseased individuals. These germs can pro- 



