ELEMENTARY CHEMICAL PHYSIOLOGY 241 



(8) Contact with oil. Receive the blood into a smooth vessel smeared 

 with oil. 



(9) Intra-vitam methods. These consist in injecting certain substances into 

 the blood-vessels of the animal before bleeding it. These substances are : 



(a) Commercial peptone, which consists mainly of proteoses. 



(ft) Soap solution. 



(7) A weak alkaline solution of nucleo-protein injected slowly the so-called 

 "negative phase" of nucleo-protein injection. 



Peptone probably acts by causing the liver -to form a large amount of anti- 

 thrombin, which normally keeps blood from clotting inside the vessels. The 

 exact action of nucleo-protein is not well understood. 



Conditions which hasten Clotting. (1) Body temperature. 



(2) The addition of some clotted blood (clot or serum). 



(3) Agitation, e.g. whipping the blood with a bunch of twigs. This is a very 

 general method of keeping blood fluid when it is not desired to study the 

 phenomena of clotting. 1 



(4) Contact with a rough surface (cf. effect of receiving into oil). 



(5) Addition of calcium salts. 



(6) Intra-vitam methods causing blood to clot within the vessels : 



(a) Injury or death of blood-vessel wall. When an artery is crushed, as 

 in a contused or lacerated wound, a clot forms, which acts as a natural plug to 

 prevent haemorrhage. When the arterial wall undergoes degeneration a clot 

 or thrombus, as it is termed, may form. Similarly, when a blood-vessel is 

 ligatured the inner coat is injured, and a clot forms for a short distance from 

 the ligature. This clotting is due to the liberation of thrombokinase from the 

 injured tissues, causing the formation of some thrombin. That the clot does 

 not extend indefinitely in the blood is due to two causes : (a) thrombin is 

 adsorbed into the fibrin it precipitates ; and (6) the formation of anti- thrombin. 



(6) Rapid injection into a vein of a strong alkaline solution of nucleo-protein ; 

 the so-called "positive phase" of nucleo-protein injection. 



Preparation of Fibrin Ferment. Blood serum, or some defibrinated 

 blood, is mixed with twenty times its bulk of alcohol. A copious white 

 precipitate is obtained. Allow this to stand under the alcohol for two months. 

 By this time all the other proteins present will be coagulated, except fibrin 

 ferment. The fluid is pipetted off, the sediment carefully collected on a 

 filter, and after the alcohol has drained off ground up in a mortar with water. 

 This extracts the fibrin ferment. Filter, and keep filtrate. 



Blood Serum 



Proteins. EXPERIMENT VI. Divide into three portions a, b, c. 



(a) Allow a to drop gradually into a beaker filled with distilled 

 water ; a cloud forms round each drop as it mixes with the water 

 This is due to the precipitation of the globulin present, as there is 

 now too little saline present to keep it in solution. 



(6) Saturate b with crystals of magnesium sulphate ; a precipitate 

 of globulin occurs. Filter. Show that the filtrate contains albumin 

 (i) by faintly acidifying with acetic acid and heating in a water- 

 bathnote the temperature at which the albumin coagulates 

 (77-79 C.) ; (ii) fully saturating the solution with ammonium 

 sulphate. 



Redissolve the precipitate of globulin in water ; faintly acidify 

 and note the temperature of heat coagulation (75 C.). 



(c) To c add an equal amount of fully saturated (NH 4 ) 2 S0 4 (half 



1 It is important to remember that this is no longer normal blood, but 

 defibrinated blood, 



8 



