478 THE POPULAR SCIENCE MONTHLY. 



may be better rewarded for their toil and their sagacity than was the 

 Babylonian philosopher ; for perhaps, by that time, the magi also may 

 be reckoned among the members of a forgotten fauna, extinguished 

 in the struggle for existence against their great rival common sense. 

 Nineteenth Century. 



THE MEDICINAL LEECH. 



By Dr. A. BEEGHAUS. 



MANY swamps and ponds, which are now considered utterly worth- 

 less, might be made sources of great profit by devoting them to 

 the production of a worm which is exceedingly valuable, and the cul- 

 tivation of which requires no expensive outlay. This worm is the 

 medicinal leech ; formerly esteemed of no value, and hated and hunted 

 on account of its bloodthirstiness, it has commanded extremely high 

 prices since its useful qualities have been recognized. Its general ap- 

 pearance is familiar, its internal structure is very wonderful. Its body 

 forms a cylindrical sac, composed of a course of about one hundred 

 rings. The terminal ring of the hinder part is broader and stouter 

 than the others, and serves as a foot. At the front extremity, which 

 is more pointed than the hinder part, are two fine, separated lips, 

 which, when brought together, form a closed ring. Several straight 

 lines run along the back for the whole length of the body, while the 

 belly is of a clearer color and is mottled with irregular dark spots. 

 The body of the leech is so elastic that it can stretch itself out to a 

 length of nearly ten inches, and draw itself up again to within the 

 dimensions of an olive. Within and back of the lipe are three thick 

 membranous pads covered with a thin, horny mass bearing several rows 

 of microscopic teeth ; they may be described as the jaws. Between 

 the jaws passes the very narrow throat, which can be opened and closed 

 at will by means of a transverse muscle. The animal derives its im- 

 portance to man from the close aggregation of the movable lips, the 

 narrow throat, and the toothed jaws, for it is enabled by this pecu- 

 liarity to break through the skin and suck the blood from it. The 

 mechanical operation is as follows : "When the lips close in a circle 

 upon the air-tight skin, the jaws are also brought down to it and their 

 saw-like teeth are pressed tight upon the cuticle. The throat having 

 now become fast closed, the head of the worm is drawn back a little, 

 and the lips are thereby given the form of an exhausted cupping- 

 glass, which is divided internally, by the jaws still fastened to the skin, 

 into three distinctly separated parts. The skin is powerfully sucked 

 up into these three divisions of the cupping apparatus till it is torn, 

 and rents are formed corresponding to the three spaces between the 

 jaws, the inner ends of which run into each other and form a larger, 



