FUNCTIONS OF THE L YMPff. 3 1 1 



The case is rather different when we come to consider the supply of 

 proteid food to the tissues. The diffusibility of the large molecular 

 serum proteids is so small that it may be disregarded, even in the 

 living body with its wonderfully perfect arrangement for allowing the 

 free contact of fluids without intermingling. Hence the only way by 

 which the tissues can obtain their supply of proteid is from the proteid 

 which has filtered through the vessel wall in the lymph. So far as the 

 proteid supply to the tissues is concerned, therefore, I believe that the 

 irrigation theory is correct, unless, indeed, we attribute to the vascular 

 epithelium the power of actively taking up proteid and transferring it 

 from one side of the vessel wall to the other in proportion to the needs 

 of the tissues. 



Even under the former hypothesis, however, we could not, from the 

 amount of lymph draining away from a part, draw any conclusions as to 

 the amount of proteid which has been supplied to the part. As I 

 have above shown, the composition of the lymph is determined by the 

 permeability of the wall and the mean capillary pressure. If the com- 

 position of the lymph be altered after transudation, in consequence of 

 an active using up of the proteids of the tissue cells, the effective 

 osmotic difference between blood and lymph will be increased, and the 

 watery and saline constituents of the lymph will be reabsorbed until the 

 original constitution of the lymph is restored. 



We may conclude, therefore, in default of definite evidence to the 

 contrary, that while the interchange between tissues and blood, so far as 

 diffusible substances are concerned, is effected by diffusion through the 

 medium of the lymph, the proteid supply to the cells is dependent on 

 the amount of proteid transuding with the lymph. 



Perhaps it is on this account i.e., increased proteid supply to the 

 cells that chronic inflammation or hypersemia of any part is apt to lead 

 to its hypertrophy. Growing tissues, as well as those in a state of repair, 

 have delicate vessels, which probably supply a lymph much richer in 

 proteids than is supplied to adult tissues. 



