144 



PHYSIOLOGY OF NUTRITION. 



in the apparatus must consequently increase. If the lower end 

 of our apparatus is allowed to dip for a certain time (one to two 

 hours) alternately into water at the usual room temperature, and 

 into warm water (say at 30 C.), we can readily prove, by observ- 

 ing the rise of the fluid in each case, that the osmotic processes 

 go on more actively at the higher than at the lower temperature. 

 If the apparatus dips not into pure water, but into a 20 per cent, 

 solution of common salt, osmosis proceeds more slowly, as may 



easily be determined. 1 



In order to under- 

 stand properly many 

 physiological phe- 

 nomena, especially 

 those caused by turgor, 

 it is of great import- 

 ance that we should 

 convince ourselves that 

 considerable pressures 

 can be set up through 

 osmotic processes. For 

 this purpose we may 

 use the apparatus re- 

 presented in Fig. 50. 

 The glass tube G, 

 10 cm. long and 2 cm. 

 in diameter, is closed 

 at the bottom with 

 pig's bladder, and dips 

 into water. Through 

 the rubber stopper 

 closing the upper end 

 of the glass tube 

 passes the T-shaped 

 tube T, the vertical 

 limb of which is con- 

 nected at a with a 

 small bent glass tube drawn out to a point at 6. The horizontal 

 limb of the T-tube is connected with the manometer M by means 

 of thick rubber tubing, bound round with wire. The manometer 

 contains mercury ; the rest of the apparatus is completely filled 

 with a nearly concentrated solution of cane-sugar, and the small 



FIG. 60. Apparatus for investigating pressure effects 

 due to osmotic processes. 



