1884.] Secretion obtained from the Medicinal Leech. 47$ 



blood does not coagulate within the living blood-vessels," the above 

 facts came to my mind and promised to throw some light on the 

 general question. 



The explanation which at once suggested itself to me was, that 

 probably the leech secretes some ferment-containing- juice which 

 antagonises the blood ferment, preventing coagulation within its body, 

 enough remaining around the edges of the wound to prevent for 

 some time the outflowing blood from clotting ; the blood remaining 

 fluid, in fact, until the leech ferment is all washed away. 



It will be seen that this explanation is in the main correct. 



In order to investigate its action on the blood, a salt solution 

 extract of leech was obtained. In the first experiment the gullets 

 and buccal cavities of two leeches were removed, cut in small pieces, 

 and placed in 5 cub. centims. of 6 per cent, salt solution. The rest of 

 the alimentary canals were also finely divided and placed in a similar 

 volume of the salt solution. The extracts obtained were of a faint 

 greenish -yellow tint, and alkaline in reaction. A leech was then 

 applied to the nose of a young rabbit for a quarter of an hour, then 

 removed, and held in a salted towel until it had disgorged. Mean- 

 while the blood flowing from the nose of the rabbit was collected in a 

 test-tube. 



The rabbit was then killed, and 3 cub. centims. of its blood received 

 into each of four vessels A, B, C, and D, which were placed under a 

 glass shade, the air within being kept moist with blotting-paper 

 soaked in water. 



Vessel A contained nothing but the blood, which coagulated in 

 four minutes. 



Vessel B contained in addition 1 cub. centim. of 6 per cent, salt 

 solution, and coagulated in four minutes. 



Vessel contained in addition 1 cub. centim. of 6 per cent, salt 

 solution of the alimentary canals (minus the pharynx) of the 

 leeches. The blood faintly coagulated in four minutes, setting* 

 completely in half an hour. 



Vessel D contained in addition 1 cub. centim. of 6 per cent, salt 

 solution extract of gullet of leeches. This remained fluid for twenty- 

 four hours, a thick clotted scum forming on the surface when the 

 blood putrefied. 



The blood collected from the nose of the rabbit and that from the 

 interior of the leech remained fluid until putrefaction set in, when the 

 same half scum half clot formed on the surface. 



It is evident from this experiment that something retarding or 

 preventing coagulation may be extracted with 6 per cent, salt solution 

 from the pharynx or mouth of the leech. 



The slight action of the rest of the alimentary canal in retarding 

 coagulation, as this and many subsequent experiments indicate, is due 



