156 
POPULAR SCIENCE REVIEW. 
foot ! This estimate would be almost incredible, if it were not 
obtained by two totally different methods of calculation, used 
as checks upon one another. And if this amount of force is 
expended by the heart in twenty-four hours, how rapid must 
be its waste, and how vigorous must be the nutrition by 
which that waste is repaired. Few instances could be quoted 
which show more forcibly than this does the wonderful per- 
fection of adaptation, and the concentration of activity which 
the higher organized structures exhibit. 
To those who are not familiar with the subject of physio- 
logical dynamics these statements, generally, will probably 
appear little short of incredible, so difficult is it for the imagi- 
nation which is untrained in the teachings of science to realise 
the fact, that the apparently simple and unlaborious functions 
of mind or body can involve the expenditure of force at all. 
The most unscientific observer cannot fail to perceive that 
the arm which works the paviour’s rammer, or the legs which 
bear the weight of the body over the many miles of a long 
day^s walk, must, in the performance of these offices, exert a 
considerable amount of force ; but he does not so readily appre- 
ciate the manifestation of the same phenomenon in the silent 
decay of the whole body when at rest, or in the unconscious 
exercise of the mind. Those, on the other hand, who h^fve 
learned with what a mighty energy nature works even in her 
most simple operations — that the force which holds the ele- 
ments of a single grain of water together is equal to that 
which is contained in a very powerful flash of lightning, will 
know that, although there are some of Dr. Haughton's calcu- 
lations which, from the uncertain state of our knowledge, 
must at present be received with some degree of reservation, 
the general character of his results is quite in unison with the 
dynamical laws which the researches of Joule, Mayer, and 
other physicists have during recent years established. 
