BLOOD 109 



Besides the red corpuscles, blood also contains a con- 

 siderable number of white corpuscles of live or six different 

 kinds. In a healthy man the proportion of white corpuscles 

 is about 1 to 500 or 600 red corpuscles, but the proportion 

 is not constant, certain kinds increasing during a meal. 

 Amongst other functions the white corpuscles, which re- 

 semble Amoebae, ingest or engulf foreign particles such as 

 bacteria, and put them out of action. Those that perform 

 this function are known as phagocytes. These cells are a 

 great help to the body by fighting and destroying the germs 

 of disease. 



Like all other cells, blood corpuscles have a definite limit to 

 their existence. After they have fulfilled their function, they 

 waste away and die. A certain number, at any rate, undergo 

 disintegration in the liver and in the spleen. To replace these, 

 new corpuscles must be formed and this possibly takes place 

 in the spleen, and certainly in the red marrow of the 

 bones. 



The total amount of blood in the body of mammals averages 

 somewhere about one-sixteenth of the total body- weight. In 

 a well grown man of 30 weighing 70 kilos there are about 

 5| kilos of blood. Many people think that it is the heat of the 

 blood which keeps the body warm. In reality it is the other 

 way about. The tissues of the body are continually but 

 slowly burning, and as the blood courses through them it 

 picks up their heat. Certain parts of the body are slightly 

 warmer than others, but the circulation of the blood tends to 

 keep the temperature fairly constant throughout the system. 

 The normal average temperature of the human body is 

 98-4 F. degrees, but it varies a little during the course of the 

 twenty-four hours, and it sinks during sleep. The temperature 

 reaches its highest in certain forms of birds. For instance, 

 the guinea-fowl has a temperature of 110° F., the pheasant 

 108-7° F., the greater titmouse 111-2° F., the swift 111-2° F. 

 These high temperatures all indicate great bodily activity. 

 Amongst mammals the duck-billed P/«^//j;?/.9 and the spiny ant- 

 eater. Echidna, the most primitive members of the class, have 

 a temperature which varies only from 2 to 5 degrees or even 

 less than a degree above that of their external surroundings. 



