THE ENERGY OF THE LIVING PROTOPLASM. 



'75 



electrical phenomena and light are the forms of energy resulting. 

 A stratum of germinating barley, 15 cm. high, at an air tempera- 

 ture of 7 0 , reaches, after a few days, a temperature of 18 0 . One 

 grin, of a stalk of Brassica liberates by respiration in one hour an 

 amount of energy equal to 132. 1 gram-meter, amounting for one 

 cell per minute to 2.2 milligram-millimeter (Rodewald). The 

 greater part of the liberated energy assumes the form of heat 

 and is dissipated. Bees produce so much heat that their hives 

 show even in winter a temperature of 30 1 . Rabbits, with a blood 

 temperature of 38 0 , consume per kilo, and per hour 0.914 grm. 

 oxygen, while chickens, with one of 43. 9 0 , consume 1.186 grm. of 

 it. Man produces every hour as much heat as would raise the 

 temperature of an equal amount of water 1.4 degrees. 



Every increase of muscular exertion requires an increase in 

 respiration ; the work done by a muscle corresponds to about 33 

 per cent of the energy yielded by respiration, while in a steam- 

 engine only 10 per cent of the caloric value is secured in the 

 form of work.' 1 ' An animal, therefore, considered as a machine, 

 works economically {Zuntz). 



Even the finest currents in the protoplasm depend upon the 

 presence of oxygen, as Kiihnc has shown, and the increased work 

 connected with a rapid development of shoots and embryos, or 

 with the transportation of starch in plants requires also an 

 increase of respiration. Further, the dependence of the produc- 

 tion of light by fungi and by various animals upon respiration 

 has been proved, and there can be no doubt also that it is the 

 same with regard to the production of electricity in the nervous 

 system and in the electrical organs of fishes. 



The function of respiration consists, not in all cases, however, 

 in merely yielding kinetic energy ; it serves also to prepare useful 



(1) The knowledge of the caloric values of the different compounds encountered 

 in organisms being of high physiological interest, Stohmann has determined them 

 with great exactness recently. We mention a few data. The caloric values of 1 

 gram amounts to, in : 



Egg-albumen 



5,735.2 cal 

 5,298.8 „ 



Peptone 

 Leucin . 

 Fat 



6,533-0 ,, 

 9.5°9-° .. 

 3-742-6 „ 



Glucose 



