666 
PHYSIOLOGY 
in the inspired, mixed expired, continuous 
(breath-by-breath), or end tidal modes. Oxy- 
gen, carbon dioxide, and nitrogen concentra- 
tions are measured by a mass spectrometer 
(MS-8, Scientific Research Instruments Corp., 
Baltimore, Md.), and carbon monoxide is meas- 
ured by an infrared analyzer (IR-215, Beckman 
Instruments, Inc., Fullerton, Calif.). Gas con- 
centrations are recorded on a strip chart oscillo- 
graph (Visicorder 1912, Honeywell, Denver, 
Colo.). 
For proceaures involving intrapleural pres- 
sures, the dogs are fitted with the face mask, 
mouthpiece, and intraesophageal catheter pre- 
viously described,*^ and for other measurements 
at rest, only the face mask is used. For testing 
in the standing position, restraining stocks'^ are 
used which hold the dog by the legs and muzzle, 
thereby imposing no restriction upon respira- 
tory movements of the thorax and abdomen 
(Figure 2). 
The dogs are brought to the laboratory in 
pairs and held in cages to await testing. During 
one visit to the laboratory, measurements asso- 
ciated with lung mechanics, functional residual 
capacity, and CO diffusing capacity are per- 
formed. On another occasion, parameters asso- 
ciated with arterial blood sampling are ob- 
tained, and tests involving treadmill exercise 
are performed at yet another time. Organiza- 
tion of the procedures in the above manner al- 
lows a relatively complete examination of pul- 
monary function, while requiring the dogs to 
tolerate the manipulations for only 10 to 15 
minutes per session. 
Dynamic pulmonary compliance and resist- 
