THE LEE( HES I >F MINNESl >T \ 



in their digestive tracts so that they could 1>c stimulated to rencwd 

 sucking on the next patient. Such treatment made every mature 

 leech available for repeated operations within a short time. The 

 practis was fraught with danger for the patients (danger of infec- 

 tion thru the leech's mouth) ; but it was a natural result. A leech 

 gorgd with blood might be satisfied for many months. A study 

 of its physiology and habits disclosd the way to greatly reduce this 

 period of uselessness. Accordingly the pleasures of the sucker were 

 multiplied by depriving him of the fruits of his labor for the financial 

 benefit of his keeper. It is interesting to note that, as stated in 

 Vol. II of the Cambridge Natural History, "The former extensive 

 use of the leech has led to the transfer of its name to the doctor 

 who employs it, the authors of the sixteenth century constantly 

 terming a physician a leech; it has been suggested, however, that 

 the term was applied rather by way of analogy.'" 



Fortunately for humanity the general practis of bloodletting 

 by means of Hinido medicinalis is a practis of the past. 



External Characters. 



The leeches of Minnesota are easily recognizd by their ex- 

 ternal features. The most prominent of the external characters 

 are a distinct sucker at the posterior end of the body and a more 

 or less evident sucker or sucker-like differentiation around the 

 mouth. When at rest the leech is elongated, more or less flattend 

 dorso-ventrally, tapering gradually toward the anterior or mouth 

 end and more abruptly at the posterior end. A fair conception of 

 the general leech form can be obtaind from the frontispiece and 

 plate A. The general outline of the leeches is quite uniform, the 

 external differences being largely differences in color, color pat- 

 terns, skin papillae and the arrangement of the annuli. The body 

 is very muscular and can be much shortend. changd in shape or 

 tightly rold up. Some species, when not swimming or crawling 

 about, actively change their outlines, often assuming many odd 

 shapes in comparatively rapid succession or holding some odd form 



for several minutes ;i t a time. This is particularly true of some of the 

 smaller, leaf-like leeches. When kept in aquaria they will often crawl 



up the die aquaria until the anterior end is just below or near 



the of the water and will then begin a series of remarkable mus- 



cular < in form may have some pysiological 



significance, such as aiding the circulation of the blood and the lymph 



