Il8 THE BLOOD 



for the number and distribution of the corpuscles and of the blood volume 

 index. This data, to be of value, must be compared with the total pro- 

 portionate amount of blood. A comparatively recent determination of 

 this question was made by methods that are modern by Keith, Rowntree, 

 and Geraghty. They injected a known quantity of a dye that is absorbed 

 with difficulty, vital red. As soon as the dye was distributed, three 

 minutes, they withdrew blood into powdered oxylate from the correspond- 

 ing vein of the other arm, centrifuged quickly and compared the stained 

 plasma obtained from the arm with a standard dilution of the dye, using 

 the colorimetric method. Computation yielded the following facts. 

 The total blood averaged 8.8 per cent., ~^ of the body weight. This is 

 about 85 cubic centimeters per kilo. The plasma averaged about 50 

 cubic centimeters per kilo. 



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 o . 23 



Brain and cord 1.24 



Kidney 1.63 



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 



The normal blood volume varies somewhat with relation to the intake 

 of food and drink. Relative body dessication would appear in extreme 

 thirst or under conditions of unusual loss of water without increasing the 

 intake, as in extreme perspiration, diarrheas, etc. 



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 semisolid 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 clot. 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, 



