62 AN AMERICAN TEXT-BOOK OF PHYSIOLOGY. 



these animals received into narrow vessels surrounded by crushed ice may be 

 kepi fluid for an indefinite time. The blood-corpuscles soon sink, so that this 

 met In id is an excellent oue for obtaining pure blood-plasma. The cooling 

 probably prevents clotting by keeping the corpuscles intact. 



2. By the Action of Neutral Salts. — Blood received at once from the blood- 

 vessels into a solution of such neutral salts as sodium sulphate or magnesium 

 sulphate, and well mixed, will not clot. Jn this case also the corpuscles settle 

 slowly, or they may be centrifugalized, and specimens of plasma can be 

 obtained. For this purpose horse's or rat's blood is to be preferred. Such 

 plasma is known as "salted plasma ;" it is frequently used in experiments in 

 coagulation — lor example, in testing the efficacy of a given ferment solution. 

 The besl -alt to use is MgS0 4 in solutions of 27 per cent.: 1 part by volume 

 of this solution is usually mixed with 4 parts of blood ; if cat's blood is used a 

 smaller amount may be taken — 1 part of the solution to 9 of blood. Salted 

 plasma or salted Mood again clots when diluted sufficiently with water or when 

 ferment solutions are added to it. How the salts prevent coagulatiou is not 

 definitely known — possibly by preventing the disintegration of corpuscles and 

 the formation of ferment, possibly by altering the chemical properties of the 

 proteids. 



.1. By the Action of Albumose Solutions. — Certain of the products of 

 proteid digestion, peptones and albumoses, when injected into the circulation 

 retard clotting for a long time. For injection into dogs one uses 0.3 gram 

 to each kilogram of animal. If the blood is withdrawn shortly after the 

 injection, it will remain fluid for a long time. The peptone solutions, on the 

 contrary, have no effect on the clotting of blood if added to it in a glass out- 

 side the body. This curious action of peptone has been much discussed. In 

 an interesting paper by Delezenne, referred to on the previous page, two 

 important facts are brought out that furnish the author a basis for a credible 

 theory of the anticoagulating effect of the injections. It has been shown, in 

 the first place, thai the peptone injections cause a marked and rapid destruc- 

 tion of blood leucocytes. Secondly, that if blood and peptone are circulated 

 together through a living liver the mixture not only docs not clot itself, lmt 

 will prevent clotting when added to freshly drawn blood. The hypothesis 

 to explain these facts and also the action of peptone on coagulation is that the 

 peptone by destroying the leucocyte- sets \'v<-c nucleo-proteid and histon (see 

 p. 61 ): the former of these by forming fibrin ferment would promote coagu- 

 lation, lmt in passing through the liver it is destroyed or neutralized in some 

 way. and the histon left in the blood isthe substance that retards the clot- 

 ting. It would be desirable, in connection with this hypothesis, if chem- 

 ical proof were furnished that histon is present in the blood after pepton< 

 injections. 



I. .Many other organic substances have an effect similar to peptone when 

 injected into the circulation or in some cases when mixed with shed blood. 

 For example, extracts of leech'- head, extract- of the muscle of the crayfish, 

 the serum of the eel, a number of bacterial toxins, and many of the soluble 



