HIRUDO. 27 



Inexperienced observers, and even some medical practitioners, less 

 accustomed to note the minutiae distinguishing the lower animals, may be 

 aided in their knowledge of the Medicinal Leech, by the accurate figure 

 of a fine specimen, Plate III. fig. 11. 



Although this animal be very often confounded with the Horse 

 Leech, which bears the greatest resemblance to it in form and habits, 

 the difference between them will be sufficiently conspicuous on compa- 

 rison. 



The Horse Leech is of coarser aspect. Its colour generally of uni- 

 form green. If variegated, it is with darker spots or speckling, often 

 different, being fainter or stronger, with sometimes a very narrow yellow 

 marginal line down each side. 



Fine specimens of the Medicinal Leech, also green, are distinguished 

 by six yellow lines of peculiar form along the back, the four interior re- 

 sembling a chain, which alone are enough of themselves to characterize 

 the animal amidst all its kindred. 



Much allowance must be made at all times, however, for the inten- 

 sity and various shades of colour, partly derived, it may be, from the 

 fluid matter lubricating the skin of such creatures. 



The Medicinal Leech is alike restless, and as voracious, as any others 

 of its kind. It can scarcely be confined, never failing to quit its vessel 

 whenever opportunity permits. But none has been subject to more 

 mistaken treatment from ignorance of its true nature, or has been the 

 source of more notorious errors. From observing it survive a long time 

 without any substantial aliment, many conclude that none is required, 

 that it may live in total abstinence. Because its position is often shifted 

 in stormy weather, it is alleged to be an infallible barometer, not only 

 for the present, but that it gives certain prognostications of wind or 

 rain. But the gradual extenuation of the Medicinal Leech amidst pure 

 water, proves its common nature with all other animals requiring food, 

 and its thirst for blood indicates the quality of its sustenance. It is an 

 animal which devours flesh greedily in confinement. The soft bodied 

 tribes denominated Vermes, MoUusca, and their congenera, besides many 

 others, are peculiarly susceptible of immediate external impresssions, or 



