INTESTINAL WORMS. 353 



want of sexual organs, of propagation, is it an impossible 

 thing for particles of matter to coalesce and form worms, 

 and thus become animate, like as the hydatid does? Is it 

 not in some such manner as this that the chyle nourishes 

 and regenerates living fibre ? To these questions, indeed, to 

 the theory altogether, Hurtrel d^Arboval has made some 

 plausible enough objections, for which I must refer my 

 reader to his work, not having room for them here. 



Production. — Peculiar states of body — certain external 

 circumstances — either conduce to, or else are consequent on, 

 the presence of worms. Poverty of body appears to be 

 favorable to their generation; the common notion being 

 that the worms themselves reduce an animal's condition; 

 though it is one that will, I believe, be found but in com- 

 paratively few cases to be true. Long residence on pasture 

 in marshy or other wet grounds has been observed to be 

 followed by worms. Stagnant water and miasms of various 

 kinds have also been thought to give rise to them. It is 

 certain that young animals are much more frequent subjects 

 of worms than either adults or such as are declining in 

 years; and that the more weakly and unthriving such animals 

 appear, the more likely they are to be or become verminous. 

 It is difficult to extract any principles, or even any plausible 

 theory, out of these several commonly admitted facts. 

 Hurtrel d^Arboval imagines that the development of worms 

 is connected with an excited or irritated condition of the 

 alimentary passages — a condition in which their mucous 

 secretion is augmented; one, he says, remarkable enough, 

 consequent on or connected with those states of general 

 debility so frequently accompanied by worms. He cannot 

 pretend to say whether the redundance of mucous secretion 

 be the cause of their production, or whether it may not be 

 owing to their presence and irritation ; but he feels himself 

 warranted in asserting that their presence is always an- 

 nounced by signs of " sur- ex citation" of the mucous mem- 

 brane itself. 



Propagation and Development. — Intestinal worms, we 

 learn from Rosen, are all oviparous; but there are, fortu- 



II. 23 



