CHAPTER XII. 
PULMONARY CAPACITY. 
1. Preliminary. 
The Spirometers employed are simply dry meters, agreeing in 
their general construction with the most approved form of those 
used for illuminating gas, and were made for the Sanitary Commis- 
sion by the American Meter Company, of Philadelphia. Their 
structure and general appearance are shown in the accompanying 
figures. Those metallic portions which are exposed to the breath 
are of copper, or some alloy which does not corrode by moisture at 
ordinary temperatures ; and they are provided with special contri- 
vances for removing the vapor as it condenses. They were tested 
from time to time, and so far as experience warrants a judgement PULMONARY CAPACITY. 
469 
they appear far superior to the cumbrous and complicated appa- 
ratus hitherto employed for the same purpose. It must not be 
forgotten that our aim was not to introduce such apparatus as would 
permit the highest degree of precision absolutely, but such as 
would, under the circumstances of the case, afford the best re- 
sults. For instruments which are to undergo the rough usage 
inseparable from transportation by army trains or on military rail- 
roads, which are in danger of being handled roughly at some un- 
guarded moment by rude men, and which must be employed at 
posts remote from facilities for repairing injuries or maladjustments, 
the conditions to be consulted are widely different from those which 
would be imposed under other circumstances. And although there 
are of course many respects in which the experience now obtained 
would indicate important modifications of method, inquiries, and 
precautions, were this work to be repeated or continued, yet the 
instruments employed have given entire satisfaction and very few 
points have suggested themselves in which the apparatus could 
clearly be changed for the better. The spirometers are graduated 
to indicate cubic inches (although cubic centimeters would be 
preferable for any future occasions), and are furnished with a 
mouthpiece of convenient form, connected with the instrument 
by flexible tubing.