CHARACTERISTIC STRUCTURE OF THE UTERUS. 425 



varied changes it is the anterior end which is most affected. It is at 



one time pointed like a cone, at another it is spherical, and again 



it is flattened like a spatula, as is the cephalic 



end of certain Planarians. It resembles the 



latter also in going first as the animal 



creeps. The more truncated posterior end 



changes its form hut slightly, and with its 



everted border, which formerly embraced the 



adherent joint like a cuff, forms a distinct 



sucker, by which the animal fixes itself fi^. 241. -Proglottides of 



during its creeping movements.^ Elongation Tcenia^ saginata in motion 



and contraction succeed one another so '°^ ' ^™'^'' 



rapidly that in a minute the joint can cover a distance of several 



centimetres. By unequal distribution of the contractions over the 



two halves of the body, the direction of motion is not unfrequently 



turned to the one side or to the other. 



The outer surface of the body is frequently wrinkled longitudinally, 

 and is of a dirty white colour. The rusty brown eggs can sometimes 

 be seen shining through the thick envelope of the body. 



The Structure of the Uterus, which, with its numerous lateral 

 branches, is so characteristic of T. saginata, is best examined by 

 treating the proglottides with acetic acid, or with caustic potash, and 

 then holding them against the light, pressed between two glass plates. 



In such preparations one observes first the median stem of the 

 uterus as a wide, though not uniformly filled, longitudinal canal 

 running up the middle of the joint. It extends forwards almost as 

 far as the outer wall, while posteriorly it stops short of it at a 



' This happens even in the segmented condition, according to an observation made by 

 Groze on T. crassicolUs (loc. cit., p. 346), which may be quoted as showing the great 

 mobility of these animals. " I hung a worm," he says, " head downwards in a long 

 cylindrical glass f uU of water, and with its posterior end attached to a thread over the 

 margin of the glass, and watched it. First it stretched out its head-bladders (suckers, 

 see Fig. 223) like the horns of a snail, as I previously observed in a segmented cystic 

 worm from the liver of the mouse (Cysticercus fasciolaris, Fig. 202). Then the border of 

 this upper part which was hanging down became for a short time crumpled, so that it 

 looked hke a Savoy cabbage ; but this movement did not last long. Thirdly, it made a 

 manoeuvre which astonished me. Feeling apparently that the water was not its native 

 element, it tried to get out. With the lower rim of the last joint of the outside portion it 

 firmly fixed itself to the glass. Then with incredible rapidity it contracted into a few lines 

 the contiguous stretch of joints which were partly under water. The breadth was thereby 

 very considerably increased to almost an inch, and this whole stretch of joints was lifted 

 out of the water. The formerly fixed joint was then relaxed, and the contracted portion 

 elongated again, so that it now hung over the glass. In the same way the middle portion, 

 and finally the cephalic end, were lifted up out of the water. In three contractions it lay 

 onthe ground near the glass. From this movement we can understand how a worm, 

 especially a human one, can work its way back into the intestine, even when it has been 

 so far expelled that a long piece of it hangs out from the rectum or anus." 



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