TiENIA. ASCAEIS. 



487 



As these worms are similar to some found in the human body, the 

 same queries hold good. 



In the autumn of 1764 I opened a dog. Upon slitting down the 

 duodenum and ileum, I found a great many tape- worms. They were 

 all alive, and crawled about while warm, but soon lost their motion 

 when exposed to the cold. I observed their motions very narrowly, 

 and could plainly see as follows : — that one link could, and often did, 

 move independently of any other ; I shall therefore confine my descrip- 

 tion to one link. This link would contract in its length, by which 

 means it would become almost circular ; then it would begin to elongate 

 at one end, which I take to be the head: this point became sharper 

 and sharper as it increased in length ; and, at last, the whole circular 

 body became changed into the long one. After the link had done this, 

 it then contracted again, as before, and repeated these motions as long 

 as it had any power to move. The effect of these motions in many, was 

 an entire separation of the link at both ends [from the other links or 

 segments of the tape- worm]. 



My next business was to observe what was to become of those links 

 that separated themselves. They still continued this motion ; by which 

 means they moved from place to place, and crawled just as another 

 worm does ; but, when laid upon a cold place, they contracted in their 

 breadth and took upon them all the shape of a round- worm or small 

 maggot. Many of them, however, contracted in length, by which means 

 they took upon themselves a particular shape. These I have, in spirits, 

 to show at any time. 



Most of these worms were tinged of a red colour. "Whether this 

 could be with the madder that the dog had. eaten, is not to be easily 

 known. 



Since that time I killed another dog that had not been fed with 

 madder, and I found some of the worms red 1 . 



In December 1764 I opened the stomach and intestines of a dog. I 

 found in the pylorus a great many worms of the round-kind ; and in 

 the jejunum I found a vast number of the tape-worm. All of this last 

 kind were small at one end : that end was fixed to the inside of the 

 intestine, and the other end was in general the thickest part of the 

 whole chain, and terminated just at once, or as if it had lost a part of 

 it. This end seemed not to be capable of holding by the inside of the 

 intestine, as the small end did; for it was loose, and seemed to be 

 carried down either by the peristaltic motion, or with the course of the 

 contents, or by both. 



1 ["In Mr. Nicholson's great dog I found them all of almost a snowy whiteness. 

 — W. 0."] 



