THE LYMPH AND ITS MOVEMENT 



75 



PRACTICAL WORK 



To illustrate the Effect of Breathing upon the Flow of Lymph. 

 Tightly holding one end of a glass tube between the lips, let the other 

 end extend into water in a tumbler on a table. In this position quickly 

 inhale air through the nostrils, noting that with each inhalation there is 

 a slight movement of the water up the tube. (No sucking action should 

 be exerted by the mouth.) Apply to the movements in the large blood 

 and lymph vessels entering the thoracic cavity. 



To illustrate Osmosis. i . Separate the shell from the lining mem- 

 brane at one end of an egg, over an area about one inch in diameter. 

 To do this without injuring the membrane, the shell must first be 

 broken into small pieces and then picked off with a pair of forceps, 

 or a small knife blade. Fit a small glass tube, eight or ten inches 

 long, into the other end so that it will penetrate the membrane and 

 pass down into the yolk. Securely fasten the tube to 

 the shell by melting beeswax around it, and set the egg 

 in a small tumbler partly filled with water. Examine in 

 the course of half an hour. What evidence now exists 

 that the water has passed through the membrane ? 



2. Tie over the large end of a "thistle tube" (used 

 by chemists) a thin animal membrane, such as a piece 

 of the pericardium or a strip of the membrane from 

 around a sausage. Then fill the bulb and the lower end 

 of the tube with a concentrated solution of some solid, 

 such as sugar, salt, or copper sulphate. Suspend in a 

 vessel of water so that the liquid which it contains is 

 just on a level with the water in the vessel. Examine 

 from time to time, looking for evidence of a movement 

 in each direction through the membrane. Why should 

 the movement of the water into the tube be greater 

 than the movement in the opposite direction ? (If the 

 thistle tube has a very slender stem, it is better to fill 

 the bulb before tying on the membrane. The opening 

 in the stem may be plugged during the process of 

 filling.) 



NOTE. With a special piece of apparatus, known as 

 an osmosometer, the principle of osmosis may be more 

 easily illustrated than by the method in either of the above experiments 

 (Fig. 32). This apparatus may be obtained from supply houses. 



FIG. 32. An 

 osmosometer. 



