TENDON SHEATHS 181 



known all other cell communities draw the material they require 

 for maintenance and growth from the blood stream. As we shall 

 see in the sequel the red blood corpuscle performs the duty of 

 oxygen carrier. No red corpuscles enter articular cartilage the 

 gristle in joints is pearly white. One can only suppose that the 

 plasma which reaches the cells from the rich vascular network 

 on the surface of the underlying bone, carries dissolved in it 

 sufficient oxygen to meet the needs of these lubricant-formers, 

 as it carries sufficient protein, carbohydrate, etc., for their use. 



The formation of cartilage and of synovia and of the relation 

 of these two substances to bone and to fibrous tissue is a rich 

 field for investigation. Certain colloidal phenomena will occur 

 to the student as suggestive of an explanation, but absolutely no 

 definite physico-chemical facts can be brought forward 'as accept- 

 able evidence. 



