WORMS. 



2G9 



numerary jaw, which is found on the left side only, is 

 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 suffer- 

 ing. I mean the medicinal Leech, of which we can readily 

 procure 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 

 implanted 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 

 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. 



THROAT OF LEECH LAID OPEV. 



