OR EQUIVOCAL GENERATION. 371 



being cured of phthiriasis by the rubbing in of oil of turpentine; 

 and it is also well known, that the Acarus scahei can also be 

 destroyed by topical applications, without any medicines taken 

 internally. Now, is it consistent with observed facts, that a few 

 external applications can so far affect the system as to cause 

 the secretions to assume a different aspect? Is it not done by 

 giving medicine internally instead of topically? Would it not be 

 more rational to ascribe the above cure to the efficacy of the 

 turpentine in destroying insect life, (spirits of turpentine will 

 kill an insect much sooner than the fumes of burning sulphur 

 or spirits of wine, I have found by experience many times,) 

 by which means it cleanses the skin from its parasites and 

 destroys their eggs and larva also? Burmeister asserts their 

 spontaneous origin in Phthiriasis, from their not being conta- 

 gious. I recollect an instance in point, with regard to Pediculus 

 mstiamenti. A person worked in a shop where several others 

 also worked, when, after having felt an unusual itching for some 

 time, which at last became intolerable, he began to search 

 his clothes, when he found one of the seams swarming with 

 this insect ; something occurred, so that he could not cleanse 

 himself from them for a day or two ; he slept in a bed with 

 another person during all the time the above occurrence took 

 place, but who was not infested with any of them : why might 

 not a spontaneous origin with regard to them be asserted, as 

 well as in Phthiriasis? This is exactly the argument put 

 forward by Burmeister. They were not contagious to his 

 bedfellow, and he knew not at the time whence they came ; 

 but it was afterwards found that one of his shopmates was 

 infested with them, which easily accounted for their appear- 

 ance. It is only from the infrequent occurrence of the Pediculus 

 tuhescentium that we are in ignorance of its production ; if it 

 happened as frequently as other external parasites, we should 

 soon become acquainted with its mode of propagation. 



If Burmeister had reflected a little upon the fate of equi- 

 vocal generation within the last century and a half, he would 

 doubtless have hesitated before he had committed himself so 

 fully upon the subject: he would have observed how it has 

 been driven from one hold after another : from the vegetable 

 it is now entirely discarded. Surely he would hardly dare to 

 assert that the various species of Cryptogamous plants, or even 

 the most humble of them, such as toadstools, mushrooms, 



