OCCURRENCE AND USES OF LEECHES 



393 



tions which are sufficiently damp for their comfort. But we 

 do not at present possess enough knowledge to state much as 

 to the facts of their distribution. The structure of leeches is 

 not so well known as is that of the earthworms ; for they have 

 not been to so great an extent collected in extra -European 

 countries. It would even be desirable to ascertain precisely the 

 species which inhabit these islands, the most recent enumeration 

 (1865) being that contained in the British Museum Catalogue of 

 non-parasitical worms by the late Dr. George Johnston. For Italy 

 this has been lately done by Dr. Blanchard, and a good many of 

 the species are common to the two countries. Johnston enumerates 

 altogether (after subtracting what are probably synonyms) 

 twenty-one species, distributed among the genera Branchellion, 

 Pontobdella, Piscicola, Nephelis, Trocheta, Haemopis, Hirudo, and 

 Glossiphonia ( = Clepsine), which number will 

 be possibly still further reduced. The first 

 two genera are marine, the remainder being 

 fresh water or terrestrial ; Trocheta has been 

 probably introduced. 



The use of Hirudo medicinalis is well 

 known to many of us from personal experi- 

 ence. So extensively was this leech formerly 

 made use of that it is now far from being 

 a common species either in this country or 

 in France. Those who desire full informa- 

 tion as to Hirudiniculture should consult 

 the work of Dr. Ebrard, published in 1857. 1 

 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 Fio. 201. Anterior end of 

 analogy. The useful blood-sucking habits SS^5fl 

 of the medicinal leech have been wrongly at- bodies. (After Whit- 

 tributed to the innocent horseleech (Aula- 

 stomum} innocent, that is to say, of the blood of Vertebrates, for 

 it has been described as " a cruel and greedy worm," engulfing 

 earthworms and even smaller specimens of its own species. 

 1 Nouvelle Monographic des Sangsues vitdicinales. Paris, 1857. 



