74 NATURAL HISTORY OF BRITISH FRESH-WATER LEECHES. 
that in 1849 they were still found in pools and wells in the 
vicinity of the same lake. He also mentions that in summer the 
leech-gatherers sat with their legs in the water and the leeches 
fastened on them. 
The supply of leeches in France at one time ran so low that 
Algerian leeches (Hirudo troctina) were imported. Their use 
was at first forbidden, but careful and extensive experiments 
•showed that no harm followed their application. These Al¬ 
gerian leeches have a number of red spots, and a faint similarity 
to the uniform of the French dragoon suggested the name of 
11 le dragon d’Alger.” They were also used in England, where 
they were called “ Trout-leeches.” 
Mr. E. M. Holmes, F.L.S., tells me that only one firm in 
London now imports leeches regularly. They are used in 
infirmaries and hospitals and in physiological laboratories, 
where the secretion “ hirudin ” is extracted and used to prevent 
the clotting of blood in various experiments. A medical friend 
informs me that they are still used in the East of London by the 
alien population in cases of neuralgia, gumboils, etc. The non- 
alien population sometimes use them for curing “ black eyes.” 
Methods ot capture and preservation of specimens.— 
Leeches should be sought amongst aquatic plants growing in 
ponds and streams and under submerged twigs and stones. 
It is best to bring them home alive, and they may be easily 
carried in corked tubes or bottles with a little water. Mr. 
Harding writes me that a good plan for obtaining the small 
species is to place quantities of weed in large aquaria. After 
two or three days the leeches crawl to the sides and may be 
picked off. Identification should be attempted before killing 
the specimens. The small species may be narcotised with 
soda water from a siphon, and if they are not kept too long 
in the carbonated water they will revive on being transferred 
to fresh water. For the larger species, the writer found that by 
carefully adding methylated spirit to the water they are in, 
the animals become narcotised. Mr. Harding advises immersion 
in water at about 120° F. For the preservation of colour 
and markings a 5% solution of formalin is best. Specimens 
required for histological work need different treatment. Castle 
(n) recommends the following method :—“ Stupefy in soda- 
