1884.] Secretion obtained from the Medicinal Leech. 485 



tions were somewhat increased and the temperature elevated, but 

 they soon recovered even after injection of large quantities ; in one 

 case a rabbit weighing only 108O grms. was hardly disturbed by an 

 injection of an extract of twelve leeches. 



The action of the leech extract, like that of the digestion products 

 of Dr. Schmidt-Mulheim, is not permanent. In a few hours the 

 blood is again normal. This may be from various possible reasons, 

 either that more and more blood ferment is excreted, overpowering 

 as it were the action of the leech extract, or that the latter is 

 oxidised and broken up in the tissues, or finally that it is excreted 

 (probably with the urine). This latter surmise was from' the first 

 held by my accomplished friend, Dr. Kobert, and the following 

 experiments show it to be true. 



The urine was withdrawn from the dog used in the last experi- 

 ment 1\ hours after the injection of the leech extract. At the same 

 time urine was obtained from a healthy animal. Two drops of each 

 fluid were added to two equal portions (7 drops) of frog's blood'. 

 Whereas the one mixed with healthy urine coagulated in 10 minutes, 

 the other remained fluid for more than 12 hours. The experiment 

 was repeated with a like result. 



Before leaving the action of the leech extract on the blood, it may 

 be well to contrast its action with the peptone injection of Schmidt- 

 Mulheim and Fano. In the first place, I should be inclined to doubt 

 whether the active substance in these investigations is peptone at all. 

 It was found that after peptone had ceased to give any reaction in 

 the blood, it was still uncoagulable ; the conclusion of Dr. Fano being 

 that it forms some compound with other blood constituents which 

 prevents the coagulation. Is it not more natural to suppose that peptone 

 has nothing to do with the question at all, especially as there are 

 many other digestion products difficult to separate from the peptone. 

 Suppose the same substance formed in the leech were present — which 

 it is not — in the digestion products, it would not have been separated 

 from the peptone prepared by these observers. At any rate, the 

 action of the injection, whatever it is, shows a marked difference in 

 its results from the leech extract. The latter produces far milder 

 constitutional symptoms, is far more powerful in its action on the 

 blood, and has the same action on rabbits as on dogs.* 



Since my return to my own laboratory I have investigated the 



* My friend Dr. Wooldridge believes that in the coagulation of the blood one 

 factor, at anj rate, is the conversion of the white cells into fibrin by the dead 

 plasma ("Proc. Koy. Soc," vol. 31, p. 413). "Without discussing the probability of 

 such a view being correct or not, it certainly is not true in the clotting of the hydro- 

 cele fluid by an extract of clot (ferment). In this case my experiments show a 

 special action of the leech extract on the ferment, which, when active, converts 

 large portions of the plasma into fibrin. . » 



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