1906.] Influence of Increased Barometric Pressure on Man. 449 



frequency. For instance, in Experiment II, M. G.'s pulse was at the rate 

 of 40 per minute at + 70 lbs., and 42 at + 63 lbs. In Experiment XIV, 

 it was 41 per minute, at +50 lbs., 30 at +30 lbs., 42 at +10 lbs., and 

 41 at + 2*3 lbs. This subject's pulse is normally slow, being rarely above 

 60 per minute in the sitting posture ; hence although there appears to 

 have been a diminution in frequency, the change is not nearly so striking 

 as in the cases tabulated by V. Schrotter (12).* L. H. found no alteration in 

 his pulse-rate at + 5 atmospheres. 



Our observations oh the blood pressure have not been at all complete. 

 The Hill and Barnard pocket sphygmometer, depending as it does upon a 

 column of air acting as an elastic spring, is not a satisfactory instrument for 

 high pressure work, the viscosity of the dense air lessening the excursion 

 of the pulse very greatly. 



We came to the conclusion that it was an important matter during the 

 decompression to move in turn every muscle and joint of the body, and to 

 change one's position frequently, so as to keep the capillary circulation active 

 in every part. In the brain, spinal cord, and abdominal organs this 

 circulation is kept active by the work of the respiratory pump. In the 

 limbs, muscles, fat of the back and chest, on the other hand, the movement 

 of the blood and lymph back to the heart depends mostly on changes of 

 posture and the expressive action of contracting muscles. The following 

 observations support these views. 



In Experiment XIII M. G. was decompressed from + 75 lbs. in 95 minutes. 

 During decompression he flexed and extended all the limb joints at frequent 

 intervals, with the exception of the knees. Subsequently pain and stiffness 

 were detected in the knees and nowhere else. 



In Experiment XIV the same subject was decompressed from + 5 atmos- 

 pheres in 120 minutes. During the compression all the linib joints, including 

 the knees, were repeatedly moved. No after effects of any kind were 

 experienced. A further difference between the two experiments was that 

 in the second a pause of about five minutes was made at each atmosphere 

 for analytical purposes. As in each of the experiments followed by pain 

 (in the case of M. G.) no such pauses occurred, it is possible, but we think 

 not probable, that these may also play a part in hindering the development 

 of after effects. 



The most interesting experiment in this connection is No. XV. L. H. was 

 decompressed from +5 atmospheres in 105 minutes, a pause of five minutes 

 being made at each atmosphere. During the decompression movements of 



* In Schrotter's cases there was no direct relation between barometric pressure and 

 pulse frequency. 



