160 PHYSIOLOGY.. 



Cold-blooded animals have lymphatic hearts which act as motors in 

 circulating the lymph. The valves in the lymphatic vessels are 

 powerful adjuvants in propelling the lymph in a central direction. 

 The respiratory movements have an influence. At the time of 

 inspiration the flow of lymph, like the blood, rushes into the chest, 

 owing to the partial vacuum in the chest. The pressure by mus- 

 cular action on the lymphatics also greatly aids in the propulsion of 

 the lymph. 



Fig. 45. Diminution of the Flow of Lymph under the Influence of 

 the Slowing of the Heart. Dog narcotized with morphia and chloro- 

 form. (L. CAMUS.) 



E, Irritation of the peripheral end of left vagus. El, Drops of lymph from 

 thoracic duct by the vertical lines, P.Cg. Pressure in left carotid equals 140 

 millimeters of mercury. 



Lymph moves at the rate of about ten inches per minute, and 

 its pressure is fifteen millimeters of soda solution. 



The nervous system bears a direct relation to the lymph-stream 

 in so far as it governs the musculature of the lymph-trunks and cap- 

 sule and trabecula3 of the lymph-glands. A solution of common salt 

 injected beneath the skin of a frog will be rapidly absorbed; but 

 when the central nervous system is destroyed, then no absorption 

 takes place. 



