Mr H. F. Baxter on Muscular Power. 209 
tions regarding the application of the principle of ‘‘ Con- 
servation Force or Energy” to organic phenomena. 
When we find it stated that the principal products of 
the light of the sun are plants, because plants can only grow 
with the help of the sun-light; that the heat of the sun is 
the cause of vegetation upon the earth; or that the mecha- 
nical power of a man may be ascertained by calculating the 
amount of carbonic acid evolved during respiration, in the 
same manuer as we might ascertain the power of a steam- 
engine by calculating the amount of heat evolved during the 
combustion of the fuel supplied to generate the steam ; as 
physiologists we cannot help feeling that some doubt must 
exist in regard to the data upon which such conclusions are 
based. For my own part, [ remember, when pursuing some 
investigations a few years ago, respecting the development 
of plants, that, upon placing some plants (beans) in a 
dark cupboard to vegetate, they grew more rapidly in the 
dark than when exposed to the light of the sun; they were 
blanched, and therefore may not, perhaps, be considered as 
in their natural state, but nevertheless they grew without 
the influence of the sun-light. It is, I believe, considered 
to be a well-known fact amongst vegetable physiologists, 
that sun-light, under certain circumstances, retards rather 
than promotes vegetation. Although I make these obser- 
vations, I do not for one moment deny the influence of 
sun-light or of heat over vegetation, or the importance of 
estimating and ascertaining the relation that the evolution 
of carbonic acid in the animal body, during respiration, 
bears to the muscular power of the individual. It is in the 
application of these facts where the doubt exists, and not 
in the correctness of the principle upon which they are 
based. 
Professor Helmholtz,* in a lecture delivered at the Royal 
Institution, has clearly and beautifully shown in a masterly 
manner the importance of applying this principle to organic 
nature. The observations that I shall now make will be 
* On the Application of the Law of Conservation of Force to Organic 
Nature. April 12,1861. I must also refer to a lecture delivered by Profes- 
sor Faraday at the same Institution, ‘‘ On the Conservation of Force.”—Phil. 
Mag., April, 1857. 
