356 Leech-lore. 



the immense numbers used in therapeutics, we shall not be sur- 

 prised that native leeches have now become very scarce, and 

 there is little doubt that the enormous demand for them, not 

 only in England but on the Continent, would in time completely 

 exhaust the natural supply, were it not that art here steps in and 

 stops the drain. Hirudiniculture, M. Moquin-Tandon informs 

 us, is now a most important branch of commerce, particularly 

 in the Grironde and other districts of the southern departments. 

 Large artificial marshes are formed, and the water is kept at a 

 uniform level ; a supply of clay and peat is made at the bottom 

 and on the sides, and aquatic plants are provided for the two in- 

 dispensable requisites of oxygenating the water, and of afford- 

 ing facilities for the leeches to free themselves of mucus, without 

 which necessary cleansing they cannot long be kept in perfect 

 health. 



Almost every one is familiar with the little triradiate shaped 

 mark left by the leech on the skin. This is effected by the 

 three teeth of the animal thus deposited in its jaws ; each tooth 

 is provided with two sharp saw-like edges, worked by powerful 

 muscles. 



The leech produces two or three fibrous-coated cocoons, 

 in which are seen a number of vitelli ; this takes place not 

 in deep water, but in moist holes or drams, at the spring of the 

 year. The whole process is doubtless a most interesting spec- 

 tacle to witness, and though we have not ourselves been spec- 

 tators of the modus parturiendi in the genus Hirudo, we have 

 been fortunate enough to observe it in the case of a closely 

 allied genus, Nephelis, a most common leech, in every brook 

 and pool in this country. Every one who has turned over 

 stones and weeds, and especially the broad leaves of Pota- 

 mogeton natans, Persicaria, Sparganium, etc., must have 

 observed some oval- shaped, olive -coloured bodies, about one- 

 third of an inch long and two lines broad. You find them in 

 every brook and pond in great multitudes all through the sum- 

 mer, fixed to stones and leaves, and within the stems of Spar- 

 ganium and other aquatic plants. What are these ? If you are 

 puzzled, you may have satisfaction in learning that so was the 

 great Linneus ! At first he took these capsules to be a species 

 of insect, to which he gave the name of coccus aquaticus. It is 

 recorded of the great Swede, that when he discovered the true 

 nature of these capsules, which for a time had so much puzzled 

 him, he exclaimed, " Vicli et obstupui. " Linneus, however, 

 does not appear ever to have witnessed Nephelis octoculata in the 

 act of producing and depositing the capsule. It is to the late 

 Dr. Rawlins Johnson, of Bristol, to whom science is indebted 

 for having been the first to record this extremely interesting 

 and curious observation. (See Philosophical Transactions for 



