122 HUMAN PHYSIOLOGY. 



in addition, numerous fatty granules, each surrounded by an albu- 

 minous envelope. When examined microscopically, the chyle pre- 

 sents a fine molecular basis, made up of the finely divided granules 

 of fat. 



COMPOSITION OF CHYLE. 



Water 902.37 



Albumin 35-i6 



Fibrinogen 3.70 



Extractives 15.65 



Fatty matters 36.01 



Salts 7.11 



Forces Aiding the Movement of Lymph and Chyle. The lymph 

 and chyle are continually moving in a progressive manner from the 

 . periphery or beginning of the lymphatic system to the final termina- 

 tion of the thoracic duct. The force which primarily determines 

 the movement of the lymph has its origin in the beginnings of the 

 lymph-vessels, and depends upon the difference in pressure here 

 and the pressure in the thoracic duct. The greater the quantity of 

 fluid poured into the lymph-spaces, the greater will be the pressure 

 and, consequently, the movement. The first movement of chyle is 

 the result of a contraction of the muscle-fibers within the walls of 

 the villus. At the time of contraction the lymph capillary is com- 

 pressed and shortened, and its contents are forced onward into 

 the true lymphatic. When the muscle-fibers relax, regurgitation is 

 prevented by the closure of the valve in the lymphatic at the base of 

 the villus. 



As the walls of the lymph vessels contain muscle-fibers, when 

 they become distended these fibers contract and assist materially in 

 the onward movement of the fluid. 



The contraction of the general muscular masses in all parts of the 

 body, by exerting an intermittent pressure upon the lymphatics, also 

 hastens the current onward ; regurgitation is prevented by the closure 

 of valves which everywhere line the interior of the vessels. 



The respiratory movements aid the general flow of both lymph 

 and chyle from the thoracic duct into the venous blood. During 

 the time of an inspiratory movement the pressure within the thorax, 

 but outside the lungs, undergoes a diminution in proportion to the 



