60 INTRODUCTION TO ZOOLOGT. 



land, but even there is rapidly disappearing. This fact is 

 mentioned by Wordsworth's leech-gatherer, in a stanza 

 which casually notices, at the same time, the manner in 

 ■which they are collected. 



" He with a smile did then his words repeat; 

 And said, that, gathering leeches, far and wide 

 He travelled ; stirring thus about his feet 

 The waters of the pools where they abide. 

 Once I could meet with them on every side, 

 But they have dwindled long by slow decay ; 

 Yet still I persevere, and find them where I may." 



Resolution and Independence, 



The supply of leeches used in these countries is derived from 

 France, Sweden, Poland, Hungary, the frontiers of Russia, 

 and Turkey; and the great extent of the trade thus carried 

 on may be judged of from the fact, that " four only of the 

 principal dealers in London import 7,200,000 annually."* 



When we find that the medicinal Leech has been applied to 

 the use of man from a remote antiquity, and now constitutes 

 so important an article of comnicrce, Ave are naturally led to 

 inquire, ' ' to what peculiarity of structure is its utihty owing?" 

 The first and most obvious is that by which its wound is 

 inflicted. Just within the margin of the mouth "are situated 

 three beautiful little semicircular horny saws, arranged in a 

 triradiate manner, so that their edges meet in the centre. "f 

 " No sooner is the sucker firmly fixed to the skin than the 

 mouth becomes slightly everted, and the edges of the saws 

 thus made to press upon the tense integument, a sawing 

 movement being, at the same time, given to each," they cut 

 their way to the sluices of blood beneath. Nearly the entire 

 body of the animal consists of a series of chambers into which 

 the blood thus taken is received. They are eleven in number, 

 perfectly distinct, and in the first eight the blood may remain 

 for months unchanged either in colour or fluidity, the creature 

 merely allowing so much to pass into the alimentary canal as 

 is necessary to preserve its existence. I Hence the repugnance 

 of the animal to repeat the operation, until the store of food 

 with which it is thus gorged has been consumed. 



The term Leech (derived from the Anglo-Saxon verb 



* Penny Cyclopedia, Article Leech. 



t Jones's Natural History of Animals, vol. i. page 322 



X Owen, page IJio. 



