WORMS. 183 



tne mothers bring forth myriads of living young. These 

 young burrow outwards into the muscles and there enclose 

 themselves in a capsule, where they remain indefinitely. If 

 this infested flesh be eaten raw, the capsule Is dissolved 

 by the stomach, the young are soon born, and they in 

 turn wander through the muscles, and, when numerous, 

 this boring into the flesh causes severe sickness, and even 

 death. The worst epidemic of this disease, known as 

 trichinosis, on record occurred near Emmersleben, Saxony, 

 in 1884. From one pig three hundred and sixty-four 

 persons were infected, and of these fifty-seven died within 

 a month. The moral which we have to learn from tape- 

 worms and trichina is that our beef and pork should 

 never be eaten raw, but should be cooked through. 



CLASS III. ANNELIDA (SEGMENTED WORMS). 



The earthworm may be taken as a representative of 

 this group, all the members of which have a marked 

 external ringing or segmentation of the body. This seg- 

 mentation also extends to the internal organs, so that the 

 whole animal may be regarded as a complex of a number of 

 essentially similar segments (also called somites or meta- 

 mcres). A little more detailed account of the structure 

 may be given. The alimentary canal (fig. 28, i) runs 

 through the body like an axis, and is suspended by a 

 longitudinal membrane, the mesentery (m) above and 

 below, while at each constriction of the body a similar 

 membrane, or septum (s) binds the canal to the body- 

 wall. The result of this arrangement of septa and mesen- 

 teries is to divide the bodv-cavitv which surrounds the 



/ . 



alimentary tract into a series of paired cavities, the 

 ccelomic pouches (c), each pair corresponding to an exter- 

 nal somite. The circulatory system consists chiefly of a 



