122 ELEMENTARY PHYSIOLOGY less, ni 



enters largely into the cause of the flow of lymph! 

 Speaking broadly lymph flows much more freely from 

 organs which are in activity than from tliose which are at 

 rest. The immediate result of this activity is the pro- 

 duction of carbonic acid and more com[)licated substances. 

 The carbonic acid no doubt diffuses rapidly into the blood 

 but the more complicated bodies accunmlate in tlie lymph 

 outside the capillaries and attract water from the V)lood by 

 the process of osmosis, thus increasing the volume of the 

 lymph at the expense of that of the blood. 



Lastly the capillary wall itself differs in character in 

 different places and is more permeable in some places 

 to particular substances than in others. 



The great majority of the known facts about the cause 

 of the flow of lymph can be explained by the physical 

 factors which have been enumerated. 



