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Cope.] 244 [Dee. 15, 
binary compound (which sets free its oxygen) liberates the chemical force 
which had previously maintained the compound, (or an equivalent force) 
which Henry regards as furnishing the growth force, which produces the 
plant. Carpenter derives but a portion of the force in this way, obtain- 
ing the greater part from the heat of the sun. To this source also he 
looks for the growth force employed in the construction of cold-blooded 
animals; while in warm-blooded animals, the retrograde metamorphosis 
or running down of the material (protoplasm) of the food, furnishes a 
requisite amount of heat. Whether growth force be derived from the 
chemism set free, direct, or through the mediation of heat, by conver- 
sion, among higher animals, is a question yet unsolved. 
Growth force we may then regard as potential in organized tissue, and 
as energetic during growth. Our present knowledge only permits us to 
believe that other force is only converted into it under the influence of 
pre-existent life, but of the real cause of this conversion we are as igno- 
rant as in the case of the physical forces. 
In the animal organism, different tissues display different degrees of 
“‘vitality.”” The most vital display cell-organization and its derivative 
forms, while the least so,’approach nearer to homogeneity. As organized 
tissue is the machine for converting vital forces, we may believe thatless 
growth force is potential in cartilage than in muscle, for it is formed by a 
retrograde process, by which cells once formed are mostly burst, and the 
contents form the intercellular, nearly structureless mass characteristic of 
this tissue. Growth force must be here liberated in some other form, 
perhaps heat, to be again converted to other use. 
The higher vitality we may believe to result from the greater perfection 
of the more complex machine as a force converter, as compared with the 
inefficiency of the more simple. 
EH. ON tHE Direction oF REPETITION. 
It has been already pointed out that growth force exhibits itself in cell or 
segment repetition. The forms in which it thus displays itself may be 
briefly considered. The approximate cause is treated of in the next 
chapter; but enough may be shown here to indicate that duplication and 
complex duplication is the law of growth force, and that therefore this 
process must always follow an increase in amount in any given locality. 
The size of a part is then dependent on the amount of cell-division or 
growth foree, which has given it origin, and the number and shape of 
segments is due to the same cause. The whole question, then, of the cre- 
ation of animal and vegetable types is reduced to one of the amount and 
location of growth force. 
Repetition is of two kinds, centrifugal and longitudinal. As an exam- 
ple of the former, the genus Actinophys has been cited, where the animal 
is composed of cells arranged equidistally around a common centre. The 
arrangement in this type may be discoidal or globular, providing no defi- 
nite axis be discoverable. As an example of longitudinal repetition, 
Vibrio, and numerous cellular plants may be cited where the arrangement 
is in a single line. 
