344 UTILITARIAN ZOOLOGY 



thread-worm {Trichina spiralis, fig. 1241). On reaching the 

 human stomach the capsules are dissolved, the minute worms 

 become adult, and myriads of larvae are produced, which bore 

 into the walls of the intestine. They are then carried in the 

 blood to different parts of the body, especially the muscles, 

 where they come to rest, and pass into the encapsuled stage. 

 Pigs contract the complaint by eating diseased rats, or the offal 

 from their slaughtered fellows, if the latter are infected. 



Personal Enemies among Hedgehog - skinned Animals 

 (Echinodermata). — Unpleasant wounds may be given by the 

 long sharp spines of some sea-urchins, especially when these are 

 provided with poison-glands (see vol. ii, p. 361). 



Personal Enemies among Zoophytes (Ccelenterata). — The 

 larger Jelly-Fishes, such as the Portuguese Man-of-war {Phy- 

 salia), possess innumerable nettling capsules, by which they can 

 inflict painful stings, of which the effects may long be felt. 



Personal Enemies among Animalcules (Protozoa). — These 

 are probably more numerous than at one time suspected. The 

 malaria-parasites introduced by means of Mosquitoes (see p. 341) 

 are the most serious at present known. 



