Absorption. 179 



lected from the thoracic duct of a cow in 24 hours has been 

 found to be 209 lbs. ! but this is no guide to the quantity 

 of lymph in the body, as the material in the thoracic duct 

 is mixed with the chyle from the intestines. It is usual, 

 however, in this vessel to consider two-thirds of the contents 

 to represent chyle and one-third lymph. The quantity of 

 mixed chyle and lymph obtained by Colin some hours after 

 the animals had been fed is as follows : 



Horse, 30 lbs. to 90 lbs. in 24 hours. 

 Oxen, 46 lbs. to 209 lbs. in 24 hours. 

 Sheep, (\h lbs. to 10 lbs. in 24 hours. 



The amount of lymph in the tissues is increased by the 

 activity of the parts, by increase in the blood pressure, and 

 by obstruction or otherwise to the free passage of lymph 

 back to the general circulation. As a rule, no more lymph 

 bathes the tissues than can be carried off by the capillary 

 lymphatics. If the irrigation exceeds the drainage capacity 

 oedema results. 



It should be noted that excessive transudation is a more 

 potent factor in the production of oedema than defective 

 drainage. This excessive transudation may be brought 

 about by obstructed venous flow (more lymph passing into 

 the spaces than the latter can get rid of), or by changes in 

 the character of the blood permitting it to pass through the 

 walls of the capillaries ; this is well exemplified in anthrax 

 and inflammatory oedema of the horse. 



The method by which the lymph passes from the blood- 

 capillary into the lymph-space is termed transudation. We 

 have before mentioned that certain physical processes, such 

 as osmosis and nitration, may assist in the production of 

 lymph, but it is to the blood pressure and the wall of the 

 vessel that the chief results are to be attributed. When 

 the lymph has passed into the lymph-space, its next move- 

 ment is towards the capillary lymph- vessel, and the methods 

 by which this is accomplished are probably by passages 

 which exist between the space and capillary, and not by 

 transudation, or, in other words, not by any purely physical 



12—2 



