HUMAN WORMS. « 109 



prone to expand and grow(49) in the fetal and in- 

 fant body, than in older and firmer subjects, on ac« 

 count of their feebler organization. Hence the 

 reason why worms are more frequent in infancy 

 and weak persons, while they arc comparatively 

 rare at adult age, and still more so in robust aud 

 vigorous constitutions. 



§. LXIX. Human worms, accustomed from 

 their origin to live in our viscera, resist their ordi- 

 nary motions, and grow there in an astonishing 

 manner ; and when expelled, they easily die like 

 fishes and other aquatic animals when taken from 

 their native element. 



It should be remarked that these intestinal 

 worms, if removed from their usual place of resi- 

 dence, either perish or are evacuated. 



Taeniae and lumbricoides, having once entered 

 into the stomach, are soon vomited up alive, or kill- 

 ed by the action of the digestive powers. 



The lumbricuides, once passed beyond the 

 valve of Baiiliin, we may consider as destroyed, 

 and they are evacuated. (50) 



^ LXX. We now see how the eggs of the prin- 

 cipal worms are introduced into the human body ; 

 since when once transported and absorbed into the 

 mass of fluids, iliey are diffused through and depos- 

 ited in the most concealed parts of the body, and 

 there enlarge and unfold when circumstances favour 

 their development. 



Vallisneri sought for the origin of all worms in 

 the first min.(;il) 



