210 ANIMAL PARASITES AND MESSMATES. 



extremity. Let us imagine the six hooks, placed in front 

 in the same direction. The two in the centre advance, 

 and the two pairs placed symmetrically by the side of 

 them, are lowered and drawn backwards, and thus push 

 the body forwards. 



"It is like the dial-plate of a clock, with three hands 

 placed by the side of each other ; that in the middle 

 would advance directly forward, while the two others 

 would be lowered until they formed a right angle with 

 the first. This is the movement which we observe in all 

 the stylets. The result of this is that we distinctly see 

 the embryo penetrate between the debris, or into the 

 crushed tissues which surround it. These embryos 

 imitate the movements of a» man who wishes to get 

 through a window a little above him, and who, having 

 succeeded in passing his elbows through, pushes his body 

 forward by leaning them on the frame. 



"We see the same efforts continue for hours; and we 

 can easily understand that there is no living tissue, 

 however dense it might be, except the bones, which 

 could not be easily penetrated by these microscopic 

 embryos. This explains why we so commonly find 

 cysticerci scattered in cysts along the intestines and 

 between the membranes of the mesentery, and how they 

 can, by piercing the walls of the vessels, spread them- 

 selves into the most distant organs, by ~ means of the 

 blood which conveys them. When the embryos have 

 once pierced these walls, they hollow out the tissues in 

 all directions, until they find themselves in the muscles, 

 or in the organ which is indicated in their itinerary. 

 When they have arrived at their destination, they stop 

 and surround themselves with a sheath ; their stylets, 



