IN MEDiCINiJ. 23 



of mice ; that of the fox is derived from the cystic worm of hares 

 and rabbits.*" 



Another very serious disease — chiefly occurring in the liver — 

 is characterized by the development of large cysts or bladders, 

 the large parent cyst often containing numerous smaller cysts. 

 For a long time, the nature of these hydated tumours was 

 unknown; but by microscopic investigation they have been 

 proved to be the development in man of the ova of the Tcenia 

 echinococcus^ a very small tape-worm, which inhabits the 

 intestinal canal of the genus Canis. Here the process which 

 takes place in the human tape-worm is reversed, the ova of the 

 tape-worm of the dog developing into the cystic worm which 

 causes hydated disease in man. 



Equally dangerous is the nematode worm, Trichina spiralis^ 

 which, although the adult male is only one-eighteenth of an inch 

 in length, and the female one-eighth of an inch, has contrived 

 lately to create quite a scare among the consumers of pork, hams, 

 and sausages. The larva of this interesting creature spends its 

 immature stage encysted in some such animal as the pig, but 

 when introduced into the stomach of some other warm-blooded 

 animal— as man — is capable of producing an immense number 

 of little TrichincB^ which swarm out of the parent by tens of 

 thousands, and bore their way in every direction, stopping at 

 nothing except bone, and finally settling down among the volun- 

 tary muscles, where they proceed to make themselves comfortable. 

 During these wanderings, they give rise to a train of symptoms 

 which somewhat resemble acute rheumatism, and is not 

 unfrequently fatal. Should this not be the case, they sooner or 

 later lose their vitality, and become converted into little particles 

 of lime, and thus a natural cure is effected. Their numbers are 

 so enormous that an unfortunate foreigner who died from an 

 accident in the London Hospital, and was found full of Trich- 

 incB^ was calculated to be acting the part of host to some 

 hundred millions. Without the microscope, it would have been 

 impossible to have discovered the cause of this disease. 



An epidemic of Trichinosis occurred at the village of Khian, 



* The head of the Beef Tape-worm has a row of suckers, but no hooklets, 

 The head of the Pork Tape-worm has hooklets as well as suckers. 



