126 



Life and Health 



Experiment 52. Simple apparatus for illustrating endosmotic 

 action^ " Remove carefully a circular portion, about an inch in 

 diameter, of the shell from one end of an egg, which may be done 

 without injuring the membranes, by cracking the shell in small pieces, 

 which are picked off with forceps. A small glass 

 tube is then introduced through an opening in 

 the shell and membranes of the other end of the 

 egg, and is secured in a vertical position by wax 

 or plaster of Paris, the tube penetrating the yolk. 

 The egg is then placed in a wine-glass partly 

 filled with water, as in Fig. 62. In the course of 

 a few minutes the water will have penetrated the 

 exposed membrane, and the yolk will rise in the 

 tube." FLINT'S Human Physiology. 



Experiment 53. Stretch a piece of moist 

 bladder across a glass tube, a common lamp 

 chimney will do. Into this put a strong sugar 

 or saline solution. Now suspend the tube in a 

 wide-mouthed vessel of water. After a short 

 time it will be found that a part of the sugar or 

 salt solution has passed through into the water, 

 while a larger amount of water has passed into 

 the tube and raised the height of the liquid 

 FIG. 62. within it. 



T 191. The Quantity of Food as affected by Circumstances. 

 The quantity of food required to keep the body in proper 

 condition is modified to a great extent by circumstances. 



1 The action produced by the tendency of fluids to mix, or become 

 equally diffused in contact with each other, is known as osmosis, a form of 

 molecular attraction allied to that of adhesion. The various physical 

 processes by which the products of digestion are transferred from the 

 digestive canal to the blood 'may be illustrated in a general way by these 

 simple experiments. 



The student must, however, understand that the necessarily crude 

 experiments of the class-room may not conform in certain essentials to 

 4hose great processes conducted in the living body, which they are intended 

 to illustrate and explain. 



