THE THREAD-WORMS. 525 



by irritating the external surface of their bodies, so 

 as to make them quit their hold, and partly by vio- 

 lent contractions in the intestines, which may some- 

 times divide their bodies, or even destroy them by 

 bruising*. Electrical shocks, passed frequently 

 through the abdomen, it is supposed might be 

 beneficial, as the lower orders of animals are in 

 general easily destroyed by electrical shocks. 



In injecting these Taenia? with coloured size in 

 order to preserve them, three feet in length from 

 the head downwards has been filled by a single push 

 with a small syringe ; but the injection would not 

 pass from below upward beyond the joint, owing, 

 as it is supposed, to a valvular aparatus situated in 

 the lateral canals immediately below the places 

 where the cross canals are sent ofFf. 



THE THREAD- WORMS. 



These troublesome animals are found in the 

 bodies of some species of quadrupeds, birds, and 

 insects. Most of the species perforate the skin im- 

 mediately under which they lodge themselves ; a 

 few, however, have been discovered in the intes- 



* There is however reason to suppose that merely breaking them, 

 unless the detached part comes immediately away, will not be alto- 

 gether effectual, as this is generally understood to be capable of pro- 

 ducing a new head, and thus becoming an independent animal. 

 + Linn, Tran. ii. 25© 



