1892.] Heredity of Acquired Characters. 889 
by the term anabolism, and the products of the different 
upward steps are called anastates. i 
Protoplasm the most complex and unstable of organic sub- 
stances is the summit of the ascending steps of the constructive 
processes, and katabolism, which represents the succeeding 
downward steps of destructive metabolism, then follows, and 
its products, or katastates, are starch, cellulose, proteids, &c., 
or what we recognize as the proximate constituents and tissues 
of plants. 
The heat developed in the nutrition of plants is also a pro- 
duct of katabolism, and it represents the difference between 
the potential energy of the protoplasm, and the potential 
energy of the other katastates formed from it. This is not 
however sufficient to enable the plants to maintain an inde- 
pendent temperature, as it is rapidly dissipated by radiation 
from the extended surface of the foliage, and a large amount 
is used in vaporizing the water exhaled by the leaves. An 
approximate quantitative estimate of the energy expended in 
exhalation was given in a paper read before section I, last year, 
and published in the May number of the Popular Science 
Monthly. 
From their greater complexity the more highly differen- 
tiated processes of nutrition in animals are not so readily 
traced, but the general course and results of metabolism, 
broadly stated, are essentially the same as obtain in plants. 
The food of animals consists of the proximate constituents of 
plants, or the katastates of plant metabolism, and with the 
exception of oxygen introduced in the process of respiration, 
they are unable to assimilate the simpler elements on which 
plants feed. 
The first demand of the animal economy is for energy to be 
used in the constructive processes, and this is derived exclusively 
from the stored energy of the organic substances of their food 
through the destructive metabolism involved in the processes 
of digestion. The proteids, fats and carbohydrates of the food 
of animals are not directly converted into animal proteids and 
fats, but the evidence indicates, as pointed out by Dr. Foster, 
that they are reduced almost to their original elements and then 
