1884.] Secretion obtained from the Medicinal Leech. 481 



One useful result of this experiment was the preparation of a 

 much purer solution to be used for experimental purposes. The 

 gullets of the leeches were placed in absolute alcohol for a day or 

 two, and then extracted with water. In this way a clear, somewhat 

 coloured alkaline fluid was obtained, almost free from albumen, and 

 giving but a very small residue, this, too, of unimpaired strength. 

 A solution prepared in this way was henceforth always used. 



The next task was to find the exact action of this substance on the 

 blood, and in the first case to see if it destroyed or hindered the action 

 of the ferment. 



After trying in vain one or two methods the following suggested 

 itself : — ' 



The blood-coagulating ferment is not very soluble in distilled 

 water, so that if a blood-clot containing it be soaked for some time in 

 the watery leech extract, this can afterwards be removed by distilled 

 water without dissolving out the ferment. On adding the latter to 

 hydrocele fluid its activity can be tested (this fluid coagulates on the 

 addition of active blood ferment). 



The washed finely divided clot from bullocks' blood was dried and 

 divided into two equal portions by weight. One portion was then 

 placed in a watery solution of leech, and the other in a like volume 

 of distilled water. After twelve hours the clots were removed, dried 

 with blotting-paper, and carefully washed in distilled water. The 

 washing lasted for three hours, the wash water being four times 

 renewed, each portion of clot being treated with the same volume of 

 water. They were then each placed in a few cubic centimetres of 

 8 per cent, salt solution in which the blood-coagulating ferment is 

 soluble. Five drops of the salt solution extract of the clots were 

 added to equal quantities (5 cub. centims.) of hydrocele fluid. The 

 hydrocele fluid to which the extract of clot, treated with leech extract, 

 had been added did not coagulate at all, while the other portion 

 coagulated in ten minutes. 



The action of the leech extract is then seen to destroy the blood- 

 coagulating ferment. 



The next question is whether the blood corpuscles are in any way 

 affected by the leech extract ? A couple of drops of blood were 

 obtained from the finger-tip, mixed rapidly with a drop of normal 

 salt solution extract of leech, and a minute drop of the mixture 

 placed on a glass slide. This was then covered, and a ring of oil was 

 painted round the edge of the cover-glass to 'prevent evaporation. 

 When this was examined on a warm stage, the red corpuscles rapidly 

 formed rouleaux in the ordinary way; and the white corpuscles 

 exhibited active ameeboid movements which continued for a consider- 

 able time — the observations lasted for an hour. In the meanwhile 

 the blood had not coagulated. It is seen then that the vitality of the 



