"Among the numerous tribes of lower animals distributed throughout 

 the universe, none has attracted equal notice perhaps as the Leech, and 

 that from the periods of the most remote antiquity. Its form, its motions, 

 its habits, are well adapted to excite the curiosity of the illiterate beholder, 

 and, above all, its utility in alleviating the afflictions of mankind have 

 gained a distinction for it which is denied to all the rest. 



Though widely known of old, in general, the detailed investigation of 

 the history of the Leech has been reserved for the latest era of scientific 

 observers, and the most advanced state of science. 



Doubtless the noted peculiarities of the Medicinal I^eech led to the 

 study of others, whether from the motives of mere curiosity or from the 

 hopes of finding them endowed with similar properties. Such expecta- 

 tions, however, have been disappointed; for among a genus, abounding 

 suflSciently in the variety of its species, I believe that no one is yet dis- 

 covered which can be so satisfactorily employed in relieving human 

 distress. 



It is true that in this country there are leeches that will suck the blood, 

 and eat the flesh of animals ; and that in some distant regions others prove 

 a kind of pest to man, but none seem as yet habituated to the same office 

 wherein the medicinal leech is so useful at home. 



Independently of the practical value of this animal, wherever it can 

 be found, certain singular facts are exposed by various species of the 

 genus Hirudo, which cannot but be interesting to the physiologist, and 

 assuredly deserve to be farther known and suitably appreciated." 



Sir John Graham Dalyell, 



" The Powers of the Creator 

 displayed in the Creation," 

 1853, p. 1. 



