244 ESSENTIALS OF CHEMICAL PHYSIOLOGY 



time attain there a greater concentration than in the blood, and so they will 

 diffuse towards the blood, by which they are carried to the organs of 

 excretion. 



But, again, we have a difficulty with the proteins ; they are most important 

 for the nutrition of the tissues, but they are practically indiffusible. We 

 must provisionally assume that their presence in the lymph is due to nitration 

 from the blood. The plasma in the capillaries is under a somewhat higher 

 pressure than the lymph in the tissues, and this tends to squeeze the 

 constituents of the blood, including the proteins, through the capillary walls. 

 I have, however, already indicated that the question of lymph-formation is 

 one of the many physiological problems which await solution by the 

 physiologists of the future. 



