DEVELOPMENT OF LIGHT AND HEAT. 497 



specific force which must be designated as vital. The first movement, i.e. tlie fii'st 

 chemical process with which respiration commences, seems to be a splitting up 

 of the albuminous molecules in the living protoplasm, the same process as that 

 by which albumen is separated into asparagin and a carbohydrate, perhaps into 

 asparagin, a carbohydrate, and carbon dioxide. The next tiling, of course, would 

 be a withdrawal of oxygen from the air, but it should be noted that this is only 

 for the purpose of continuing the metabolic changes, which have originated spon- 

 taneously in the living protopla.sm. 



Heat likewise is liberated in all combination of oxygen with other substances, 

 especially in every combustion of carbon compounds. This heat is not always 

 easUy demonstrable in the plant organ in which it is set free. The heating of 

 the respiring tissue is counteracted by the evaporation of water and by i-adiation 

 in organs above-ground, particularly in the flattened, outspread foliage-leaves. 

 Carbon is also reduced in the green foliage during the day under the influence 

 of sunlight, and this is a process which goes hand in hand with the fixing of 

 sensible heat. Now, since this process masks the respiration in the green leaves 

 to a certain extent, it is intelligible that the heat liberated by respiration in these 

 organs is but seldom perceptible, and that as a rule green leaves actually feel 

 cool. It is even probable that the pleasant coolness under a shady canopy of 

 leaves is not solely due to the interception of the sun's rays, but that the imprison- 

 ment of these rays and the fixation of heat during the manufacture of the 

 primary carbohydrates also shares in the cooling of the air surrounding the 

 leaves. But where these conditions are out of the question, the heat liberated 

 can be demonstrated in respiring vegetable organs just as iu animal bodies; and 

 if respiring green leaves could neither transpire, nor radiate heat, and if, moreover, 

 a supply of carbohydrates were stored up in them, the heat liberated by respira- 

 tion would make itself evident in the immediate neighbourhood. This applies 

 still more to subterranean bulbs and tubers in which transpiration and radiation 

 are not only partly or entirely absent, but which are incapable of manufacturing 

 carbohydrates for themselves as they have no chlorophyll, and which, conse- 

 quently, render no heat latent. 



Germinating seeds, and seedlings without chlorophyll behave in the same way 

 as these respiring underground organs, provided that they are protected against 

 evaporation and radiation. Barley-coms which have begun to germinate and 

 are respiring vigorously raise the temperature of their environment quite notice- 

 ably if they lie heaped together so that the heat liberated becomes thus concen- 

 trated. It is well known that malt is germinated barley, and in the preparation 

 of malt heaped-up barley-corns are caused to germinate. In this process the 

 temperature of the immediate neighbourhood rises 5-10° C. above the temperature 

 of the air which surrounds the piles of barley-corns outside. The liberation of 

 heat in fungi is also veiy instructive. These derive the organic compounds from 

 which they build up their mycelia and fruit bodies from other living organisms, 

 or from the decaying remains of dead plants and animals. The receptacles often 



Vol. I. 32 



