So 
Dr. Carson on the 
extent of that power, as it is applied in the living system, 
could be calculated. 
It was conceived that it would be a matter of no small im- 
portance to ascertain the extent of a power which, as I believe, 
discharges a part of the first importance in the scheme of 
life. With that view, a number of experiments have been 
performed, which I hope will be found to determine, in a con- 
siderable number of animals, the extent of the elasticity pos- 
sessed by the lungs in their state of expansion in the living 
and sound body ; or the extent of a power by which the heart 
and diaphragm, and perhaps various other organs, are as 
necessarily and as effectively influenced as the piston of the 
steam engine is by the expansive powers of steam. 
To enable those Gentlemen who may not be familiar with 
the anatomy of the parts concerned, to perceive the tendency 
and import of these experiments, and to understand the argu- 
ments that may be advanced, it may be necessary to premise 
the narration with a short and general description of the 
structure, position, and connections of the lungs. It is hoped 
that no person, who has at all applied his attention to mecha- 
nical philosophy, will find any difficulty in comprehending 
this description of a simple but beautiful machinery. 
The appearance of the lungs, or, in common language, the 
lights of oxen and of other animals slaughtered for the use 
of man, is familiar to every one. They are that irregular 
pale red spongy mass, which is daily seen suspended in the 
shambles by the windpipe. The windpipe, or in the language 
of anatomists, the trachea, which is a necessary appendage to 
the lungs, extends from the throat to the top of the chest. 
