50 HIRUDO. 



Though active in the finer season, these animals generally shun the 

 light ; its presence seems to create uneasy sensations. But it must appear 

 somewhat remarkable, that in the Hirudn muricata or Skate Leech, no 

 organs of vision have been as yet discovered. 



Leeches are extremely dependent on the temperature of the atmo- 

 sphere. What is genial to most other animals is refrigerating to them, and 

 at a very moderate degree torpor succeeds activity. All are extremely 

 voracious whenever opportunity offers, greedily devouring fish, flesh, and 

 other animal substances. Nor are the succulent parts of vegetables al- 

 ways rejected. Their voracity is such that they obviously perish of 

 mere repletion. The muricata, mcdicinalis, and sanguiwga absorb blood 

 in great quantities, but it does not seem to be the aliment of some 

 others. We have seen how bold and insidious an enemy one may be, from 

 which there is no escape, and which nothing less than the life of its 

 victim can satisfy. 



A few breed readily in confinement, but rarely those the most valuable 

 to mankind. Of others it seems almost impracticable to obtain the pro- 

 geny. The propagation of a few, however, discloses some interesting facts 

 in physiology. 



It is a cruel and a common error, to believe that the Medicinal 

 Leech can sustain life on water alone, and that withont renewal. Un- 

 equivocal symptoms demonstrate that emaciation is inseparable from 

 abstinence, and that nothing is so grateful as general warmth and the 

 renovated element. 



It does not appear that the history of the leech has advanced in pro- 

 portion to the number of the literati who have rendered it the subject 

 of discussion. 



