30 
RETORTS OF SOCIETIES. 
medicinal leech secretes from its sucker and gullet a juice which has 
the peculiar property of preventing the coagulation of blood. This 
juice can be extracted with water, and if the extract be added to 
blood, freshly drawn, this remains permanently fluid, instead of 
clotting in the usual way. The coagulation of blood is due to the 
formation of a substance called fibrin, by the action of a specific 
ferment. This latter is destroyed by the leech extract. On inver¬ 
tebrate blood, when the clotting is due to another cause, the secretion 
has no action. From experiments which he had recently performed 
iii Germany, the Professor found that an extract of three or four 
leeches, injected into veins of a living dog or rabbit, produced well 
marked fluidity of the blood, and other symptoms more interesting to 
the physician than to the naturalist. In the leech’s own economy the 
juice plays an important part. As is well known, the blood “ sets” in 
a solid mass around the edges of an ordinary wound—say that produced 
by a razor cut. This stops the continuous bleeding which would 
otherwise follow. Now but for this juice, which flows from the sucker 
into the wound when the leech bites, the creature would suck in vain. 
After the first few drops had exuded no more would flow, and that 
which had passed into its gullet would set into an indigestible clot. 
One can now explain why, when the leech is removed, the wound 
continues to bleed often for a very long time ; its edges are impregnated 
with the juice, and clotting only occurs when this has been all washed 
away.—A discussion followed, in which the Chairman, and Messrs. 
W. R. Hughes, R. W. Chase, T. Clarke, France, Cullis, and others took 
part. Professor Haycraft also presented to the Library of the Society 
a copy of his paper as read before the Royal Society. Microscopical 
General Meeting, December 16th.—Mr. C. Pumphrey exhibited, by 
the aid of the lantern, a series of photographs taken by him during his 
journey and visit to Canada and America. The first was a view of the 
Liverpool Docks, then several pictures taken on board the steamship 
“ Vancouver ” during the voyage to Quebec, such as groups of 
passengers, some in repose, others occupied in games to pass away the 
time ; then waves and icebergs. On arriving at Quebec Mr. Pumphrey 
did not go on to the meeting of the British Association, but made his 
way to the Yellowstone Park, a large tract of land about sixty miles 
square, set apart by the Americans as a park for ever ; it is reached by a 
southern branch on the North Pacific Railway. He also exhibited several 
views taken on the way, such as an Indian town with its wigwams, the 
city of Winnipeg, interior of a Pulman car, and interior of a dining 
saloon in a steamboat on Lake Superior. Arriving at the Park there 
was the Mammoth Hotel, containing a thousand beds, and another 
hotel, which was composed of canvas tents only. Views were given of 
the hot springs, showing the peculiar shapes assumed by the tufa, 
formed by the lime from the hot water ; also views of the geysers, 
showing how they deposited siliceous matter; but the grandest views 
were those taken of the great canon, or ravine, which is about one 
thousand feet deep, and at the top one mile wide. Through this 
the Yellowstone River runs, and in one part it falls three hundred 
and fifty feet. Here the scenery is grand, and Mr. Pumphrey has 
obtained several good pictures. The exhibition was very interesting 
and instructive, and as only half the pictures were shown the members 
will have an opportunity of seeing the others on some future occasion. 
BIRMINGHAM MICROSCOPISTS’ AND NATURALISTS’ 
UNION. - November 17tli.—Mr. Madison exhibited various specimens 
