THE BLOOD 



tion; the difference in the weight representing the quantity of blood which 

 escaped. The blood-vessels of the head and trunk were then washed out 

 by the injection of water until the fluid which escaped had only a pale red 

 or straw color. This fluid was then also weighed, and the amount of blood 

 which it represented calculated by comparing the proportion of solid matter 

 contained in it with that of the first blood which escaped on decapitation. 

 Two experiments of this kind gave precisely similar results (Weber and 

 Lehmann). 



This quantity of blood is distributed in the different parts of the body, 

 chiefly in the muscles, the liver, the heart, and larger blood-vessels, as shown 

 by the following figures determined on the rabbit by Ranke (from Vierordt) : 



Per cent. 



Spleen 0.23 



Brain and cord i . 24 



Kidney i . 63 



Skin 2.10 



Abdominal viscera 6. 30 



Cartilage 8 . 24 



Heart, lungs, and large blood-vessels 22.76 



Resting muscle 29 . 20 



Liver 29.30 



It should be remembered, in connection with these estimations, that 

 the quantity of the blood must vary very considerably, even in the same 

 animal, with the amount of both the ingesta and egesta of the period im- 

 mediately preceding the experiment. It has been found, for example, that 

 the quantity of blood obtainable from the body of a fasting animal rarely 

 exceeds a half of that which is present soon after a full meal. 



COAGULATION OF THE BLOOD. 



The most characteristic property which the blood possesses is that of 

 clotting or coagulating. This phenomenon may be observed under the 

 most favorable conditions in blood which has been drawn into an open vessel. 

 In about two or three minutes, at the ordinary temperature of the air, the 

 surface of the fluid is seen to become semi -solid or jelly-like, and this change 

 takes place, in a minute or two afterward, at the sides of the vessel in which 

 it is contained and then quickly extends throughout the entire mass. The 

 time which is occupied in these changes is about eight or nine minutes. The 

 solid mass is of exactly the same volume as the previously liquid blood, and 

 adheres so closely to the sides of the containing vessel that if the latter be 

 inverted none of its contents escape. The solid mass is the crassamentum 

 or dot. If the clot be watched for a few minutes, drops of a light, straw- 

 colored fluid, the serum, may be seen to make its appearance on the surface, 

 and, as it becomes greater and greater in amount, to form a complete super- 



