I12 BOTANICAL GAZETTE [FEBRUARY 
oxides and the heat, as wastes. Although inevitable they are not 
essential; some of them, possibly all, are dangerous, and for this 
reason to be eliminated as quickly as possible. 
The bodies of animals are compact masses compared to the 
bodies of plants. From the extensive surface of the plant body 
radiation is rapid; from the limited surface of the higher animals, 
it is slow. The plant needs no forced draft to carry off its waste 
heat; the massive animal does. The submersed animal is in a 
medium which: quickly absorbs heat; it needs little else than the 
water it lives in to relieve it of its waste heat, as well as its waste 
oxides. Its simple circulatory system is adequate. But air absorbs 
little heat; it is indeed a fair insulator as compared with water, as 
the bather in cold water knows by experience. 
The liberation of heat may be used, liké carbon dioxide, by the 
physiologist as a gauge of the activity of respiration, but like car- 
bon dioxide, it must be regarded by him as an end product, a 
waste, and not the essential product. The essential product of 
‘respiration may be energy, but if so, it is that energy which is 
/immediately convertible, and is converted into work by the organ- 
‘ism. On the other hand, respiration may be essentially a process 
.of purification, in which useless or injurious substances are con- 
/verted into forms which can be eliminated. The liberation of 
_ energy accompanies these oxidations. Some of this energy may 
(be useful and used; much of it is useless and is eliminated. Elimi- 
nation by radiation is sufficient in organisms of extensive area in 
proportion to their mass. Radiation is insufficient for organisms 
of small area in proportion to the mass. In these the circulatory 
and so-called respiratory systems are employed to eliminate heat 
as well as the material products. 
In this study of heat liberation, therefore, I believe I have been 
occupied with an unessential, although inevitable, feature of the 
process of respiration. The essential part of the process of respira- 
tion is much more likely to be found to be chemical and not physi- 
cal. And if this is made any more evident by this study, my work 
is not in vain. 
LELAND STANFORD JUNIOR UNIVERSITY 
