288 



PHYSIOLOGY OF NUTRITION. 



perforated filter, and then the seedlings which we wish to examine 

 with reference to their spontaneous development of heat. The 

 tubulus of the bell-glass is fitted with a 

 cork through which passes the thermometer 

 Tm, fixed so that the germinating seeds 

 completely surround its bulb. The seed- 

 ling material is easily obtained by laying 

 seeds (Pisum, Triticum), after soaking, on 

 clamp blotting-paper, when germination at 

 once begins. We fit up a second apparatus 

 in exactly the same way, filling the funnel, 

 however, not with developing plants, but 

 with paper balls which have been soaked 

 in water. I experimented, e.g., with wheat 

 seedlings, four days old, placed in a funnel 

 of about 200 c.c. capacity. The thermo- 

 meter after some time indicated a tempera- 

 ture of 19 C., while the thermometer in 

 the funnel containing moistened paper 

 pellets only registered 17 C. The seed- 

 lings were thus 2 C. higher in temperature. 



PIG. i07.-A PP aratus fc r Usin the aboye form of apparatus we 

 proving the production of need not fear that the material will suffer 



heat by plants. fr()m wfljit Qf Oxygenj since it ig not air . 



tight, and the Carbon dioxide produced is absorbed by the 

 potash. On the other hand, it is important to put the apparatus 

 together, and introduce the seedlings and paper pellets re- 

 spectively, some hours before the thermometer readings are to 

 be taken (e.g. in a lecture). It is likewise necessary, before 

 making the experiments, to carefully compare with one another 

 the two thermometers which we use. It is also instructive to 

 experiment with flowers instead of seedlings, e.g. flowers of 

 Anthemis or Bellis. The development of heat in these is fairly 

 large. 



To prove that heat is liberated in the alcoholic fermentation set 

 up by yeast, we simply proceed as follows. We prepare two 

 cylinders A and B. In A we place 300 c.c. of Pasteur's food 

 solution (for its preparation see 18) ; in B 300 c.c. of water. In 

 both fluids is placed a considerable quantity of yeast, and they 

 are then kept at a temperature of about 24 C. When active 

 fermentation has been set up in cylinder A, we determine the 



