LYMPHATICS 107 



fin t, they .ire young colourless corpuscles which are being formed 

 by the division of corpuscles into two, and then each of these 

 two into two more, and so on. The lymph flows through this 

 meshwork, and some of the leucocytes are carried away in the 

 stream. In this way the lymph brings new colourless cor- 

 puscles to the blood. All the colourless corpuscles of the blood 

 arise in this way from lymphatic glands or from similar tissue 

 elsewhere. 



In addition to the plasma of the blood which passes out of 

 the capillaries to form lymph, some colourless corpuscles pass 

 out, between the endothelial cells, with it, so that there are 

 colourless corpuscles throughout the lymphatic system. 



From the blood in the capillaries, and by means of the 

 lymph, the tissues obtain all they require for their life. What 

 those substances are we shall learn later, but one of them is 

 oxygen. Similarly the tissues return their waste products to 

 the blood, and one of these is carbonic acid. The supply of 

 oxygen and the withdrawal of carbonic acid is carried out by 

 respiration, which we will now consider. 



