WORMS. 269 



small, semicircular, toothed, and placed between the second 

 and third pairs. All these pieces are surpassed by 

 the margin of the proboscis, which is often hard and 

 black." * 



From this complex and formidable mouth we will pass 

 to one of quite another form, not less effective, perhaps 

 more formidable, but ordained by the goodness of God to 

 be a most valuable agent in the relief of human suffering. 

 I mean the medicinal Leech, of which we can readily pro- 

 cure a specimen from our friend the apothecary. 



Here it is. There is no protrusile proboscis, but the 

 throat is spacious, and capable of being everted to a slight 

 degree. The front border of the mouth is enlarged so as 

 to form a sort of upper lip, and this combines with the 

 wrinkled muscular margin of the lower and lateral portions 

 to form the sucker. With the dissecting scissors I slit 

 down the ventral margin of the sucker, exposing the whole 

 throat. Then the edges being folded back, we see im- 

 planted in the walls on the dorsal region of the cavity 

 three white eminences of a cartilaginous texture, which 

 rise to a sharp crescent- 

 shaped edge ; they form 

 a triangular, or rather a 

 triradiate figure. 



Now, if you recollect, 

 this is the figure of the 

 cut made in the flesh 

 wherever a Leech has 

 sucked, as it is of the 

 scar which remains after 



... , , , THROAT OF LEECH LAID OPEN. 



the wound has healed. 



For these three little eminences are the implements with 

 which the animal, impelled by its blood- sucking instincts, 

 effects its purpose. But to understand the action more 

 perfectly, we must use higher powers. 



* " Litt. de la France," ii. 138. 



