182 



HITCHCOCK'S ANATOMY 



Fig. 188. 



Illustration of the Principle of Ven- 

 turi. When a current passes through a 

 large tube, if another smaller tube open 

 into its side, the current in this tube 

 will be drawn into the large tube, even 

 against the force of gravity. 



rower to the wider portion, 

 if the vertical tube be made 

 to dip into a vessel of water, 

 not only will the water of the 

 larger pipe not descend into 

 the vessel, but it will draw 

 up the water through the* 

 small tube so as to empty 

 the vessel.' 7 This is called 

 M the principle of Venturi," 

 and is well illustrated by the 

 entrance of the Thoracic Duct 

 into the Subclavian vein, as 

 seen in the cut No. 187. A 

 diagram illustrating the same 

 principle is seen in Fig. 188, 

 the arrows representing the 

 direction of the currents, and 

 the smaller, perpendicular 

 tube illustrating theThoracic 

 duct at its entrance between 

 the veins of the neck. 



331. The Lymphatics. — The Lymphatics in general 

 structure and function resemble the lacteals. The lacteals, 

 however, are designed exclusively for promoting the growth 

 of the body by adding nutrient materials, while the lympha- 

 tics give up to the general circulation not only useful pro- 

 ducts, but all those w r hich are absorbed. Hence whatever is 

 presented to the mouths of the lymphatics, is carried into the 

 general system, while injurious products are not usually taken 

 up by the lacteals. (See also page 284.) 



332. The Action effected by the Lymphatics. — Since 

 the Lymphatics, as already described, are found in every 



Illustrate the principle of Venturi. 331. Give the general structure of the Lympha- 

 tics. State the probable differences in function between these and the Lacteals. 



