462 



WORMS. 



EGG (a) AND SIX-HOOKED EMBRYO (6) OR 



Proscolex OF TAPE-WORM. 



numbers and minute size, some ultimately succeed in making their way in 

 connection with either food or water into the stomach of an ox. Here the egg- 

 shell is dissolved by the action of the digestive fluids, and a small embryo, the 

 proscolex, is set free. This embryo is a small round creature furnished with six 

 hooks, arranged in three pairs. Upon this proscolex the gastric and intestinal 

 juices have no effect ; but instead of undergoing further development in the 

 alimentary canal of the ox, it bores by means of its hooks into the blood-vessels of 

 its host, and is thus carried by the circulation into the muscles, liver, lungs, brain, 

 or other suitable resting place, where it starts its growth. Here it elongates, 

 and becomes larger, while the hooks drop off and the central portion liquefies, so 

 that a bladder of fluid is formed. When these bladders — which are oval and 

 about a quarter of an inch in length — are found lying side by side between the 

 muscular fibres of beef, the meat is spoken of as measly. The next step is the 



formation of the head, which takes place in the fol- 

 lowing way. At one spot on the side of the bladder 

 an infolding of the outer skin takes place, and this 

 elongates until converted into a hollow sac project- 

 ing into the cavity of the bladder. At four 

 equidistant points near the bottom of the pushed-in 

 sac the suckers of the head appear. The head 

 therefore is developed outside-in, but subsequently 

 it is pushed out, and the embryo, which in this stage 

 is termed Cysticercus bovis, consists of a head, a neck, 

 and a bladder. Beyond this stage the tape-worm cannot go so long as it remains 

 in the body of the ox. If, however, the latter be killed for food, and its affected 

 flesh eaten in an uncooked state, the bladder and neck of the Cysticercus are 

 dissolved by the digestive fluids, while the head, which 

 is often spoken of as the scolex, fixes itself to the walls 

 of the intestine, its neck gradually elongates, and the 

 body grows and becomes divided into segments, or 

 proglottides. Another common tape-worm in Europe is 

 T. solium, which is scarcely so long as T. saginata, and 

 may be distinguished by the presence of a circlet of hooks 

 on the head in front of the suckers, as well as by the 

 smaller number of egg-sacs in the ripe segments. It has 

 long been well established that human beings share with 

 pigs in the breeding of this tape- worm, the bladder worm 

 stage (cellulosce) being found in one of these quadrupeds, 

 and the cycle of development similar in all respects to 

 that of T. saginata. In addition to being found in swine, 

 the bladder- worm stage of T. solium also occurs in a few 

 other animals, such as monkeys and dogs ; and even in 

 man, if through any accident an egg has been swallowed, 

 the Cysticercus duly makes its appearance in the muscles, 

 heart, brain, or eye, and may thus be the cause of very serious consequences. 

 Another tape- worm (T. cucumerina), sometimes found in man, frequently lives in 



BLADDER-WORM STAGE (Cysti- 



cercus) of tape-worm. 



a, With head beginning to turn ; 



b, With head protruded. 



