HIRUDO. | 27 
Inexperienced observers, and even some medical practitioners, less 
accustomed to note the minutiz 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 alonggthe 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, Mollusca, and their congenera, besides many 
others, are peculiarly susceptible of immediate external impresssions, or 
