ABSORPTION 177 



increase of pressure in the capillaries as the result of the venous 

 obstruction, but also the venous blood is kept in contact with the 

 wall of the capillary, and this induces changes in the epithelioid 

 cells resulting in increased lymph formation. The swollen legs 

 so common in horses kept idle in the stable are due to this cause. 

 The venous blood ascends the limbs against gravity, and exerts 

 on the capillaries of the legs below the knees and hock a pressure 

 which is nearly equivalent to the height of the vein ; as a result, 

 the cells of the capillary wall are the seat of an increased exuda- 

 tion, and the legs accordingly ' fill/ a condition at once removable 

 by exercise. The pressure in a lymph-vessel is low ; in the neck 

 of the horse it was found to be from \ to § inch of a weak solution 

 of soda ; in the dog the lateral pressure was half that found in 

 the horse. 



The lymph moves slowly in its vessels. Weiss has observed 

 a rate of from 230 to 280 mm. (9 to 11 inches) per minute in a 

 large lymphatic in the neck of the horse, but the velocity in the 

 small vessels is very much less. Colin observed 120 mm. 

 (4! inches) per minute. The flow from the thoracic duct of a 

 calf was found by Colin to be 1 metre (3 feet 3 inches) a minute ; 

 in a large mesenteric vessel the same observer found the velocity 

 to be 840 mm. (33 inches) a minute. 



