546 LECTURE XXIII. 



fact that coagulation does not take place cannot be due to an insufficient 

 adhesion. The uninjured walls of the blood-vessels appear to exert a 

 restraining influence upon the coagulation. It is indeed possible that 

 they also produce a secretion of a negative catalytic nature. 



We have mentioned that it is possible to prevent the clotting of blood 

 outside of the body by collecting it in a solution of ammonium oxalate. 

 Sodium fluoride acts similarly. The cause of the failure of coagulation to 

 begin is to be considered as due to the precipitation of the lime-salts 

 as oxalate or fluoride. The addition of neutral salts in sufficient concen- 

 tration, or cooling the blood, also tends to prevent the formation of a clot. 

 The influence of both measures is due to a restraining of the action of the 

 ferment. Now we know of a number of substances which may be intro- 

 duced into the circulation so that the blood which is subsequently removed 

 will not coagulate. Commercial peptone is such a substance. 1 We may state 

 in this connection that peptone acts differently in the case of different 

 animal species, and in fact with one individual of a species it may prevent 

 coagulation, in another merely retard the formation of coagulum, while 

 in a third member of the same species it will be apparently without effect. 

 This indicates that the influence of peptone upon the process of blood-coagu- 

 lation is not so simple as is the case with oxalic acid for example. It is 

 important also to find that it takes from ten to fifteen times as large a dose 

 of peptone to prevent the coagulation in a test-tube as is required in the case 

 of injection into the organism. It has never been found possible to localize 

 in any way this action of the peptone, although apparently, in the light of 

 recent investigations, the action is not due to the peptone itself, but to 

 impurities present in commercial peptone. How this effect is produced 

 is entirely unknown to us. It has been suggested that it causes the for- 

 mation in the body of substances which tend to prevent the coagulation. 

 It has been established that peptonized blood contains all the elements 

 which are considered as necessary for the clotting. In spite of this fact 

 the harmonious course of the entire chain of processes is in some way 

 disturbed. We can indeed imagine that by the failure of some one 

 of the substances which aid in the coagulating process, the clotting is 

 prevented. The disturbance is at all events to be sought in the group of 

 processes by which the activating of the zymogen of the fibrin-ferment is 

 effected. 



Other substances are known which act similarly to peptone. We will 

 mention the serum of Murcena 2 and the extract of crabs' muscles and of 



1 Schmidt-Miilheim: Arch. Anat. Physiol. 180, 33. Albertoni: Zentr. mecL 

 Wissensch. 1880, No. 32. Fano: Arch. Anat. Physiol. 1881, 277. 



2 Mosso: Ann. chim. farm. 8, 198 (1888), and Arch, exper. Path. Pharm. 25, 111 

 (1891). Delezenne: Arch, physiol. 646 (1897), and Compt. rend. soc. biol. 49, 42 and 

 228 (1897). Heidenhain: Pfliiger's Arch. 49, 209. 



