480 Prof. J. B. Haycraft. On the Action of a [Apr. 3, 



to some of the secretion diffusing downwards. Its place of origin 

 within the body of the leech is certainly the pharynx or buccal 

 cavity, decoctions of which are more than ten times as strong as those 

 of the rest of the body. 



The next experiment was undertaken to test my supposition that 

 this substance belonged to the class of ferments, the most general 

 character of which is that they are destroyed by boiling. At the 

 same time solutions of the leech in distilled water were made in order 

 further to test its solubility. 



Equal portions of the blood of a sheep were placed in four vessels 

 containing equal volumes of leech extract. 



Vessel A contained salt solution extract of gullet of leech ; the 

 blood remained fluid for three hours and was not further observed. 



Vessel B contained distilled water extract of gullet; the blood 

 remained fluid for a like period. 



Vessel C contained toiled salt solution extract ; the blood remained 

 fluid for a like period. 



Vessel D contained boiled distilled water extract ; the blood 

 remained fluid for a like period. 



The blood received in a test-tube from the body of the animal 

 coagulated in five minutes. This experiment was repeated with 

 similar results. 



We have then to do with a substance not a ferment, and soluble in 

 distilled water, as well as in salt solution. 



It may be noted that when the leech extracts are added to blood the 

 corpuscles subside to the bottom of the vessel, leaving, in the case of 

 the salt solution extract, a clear plasma, and in the case of the watery 

 extract a plasma coloured by the haemoglobin, which is partly dissolved. 



In order to obtain the active principle of the leech extract in a pure 

 form an attempt was made to isolate it by means of the ordinary 

 solvents. 



A watery extract of several leeches was evaporated to dryness, and 

 divided into portions which were respectively extracted for twelve 

 hours with chloroform, ether, benzole, and absolute alcohol. They 

 were then filtered, and the filtrates evaporated to dryness and ex- 

 tracted again with water. They had no action whatever on blood, 

 except in the case of the chloroform extract, and that was very slight 

 indeed. 



The residues after extraction with these fluids were dissolved in 

 water, and proved efficacious when added to blood. 



The substance is then insoluble in chloroform, ether, benzole, and 

 alcohol. 



Its separation in a pure form being evidently a difficult matter 

 owing to its insolubility in the most useful solvents, the attempts at 

 its isolation were in the meanwhile abandoned. 



