The Influence of Increased Barometric Pressure on Man. 21 



of the gradually varied conditions present in the district where coagulation 

 is taking place. 



EEFEEENCES. 



A. B. Macallum, "On the Distribution of Potassium Salts in Animal and Vegetable 



Cells," < Journal of Physiology,' vol. 32, pp. 96-128, 1905. 

 A. B. Macallum and Miss Menten, " On the Distribution of Chlorides in Nerve Cells and 



Fibres," 'Koy. Soc. Proc.,' B, vol. 77, pp. 165-192, 1906. 

 Albrecht Bethe, " Allgemeine Anatomie und Physiologie des Nervensystems," pp. 272-298, 



Leipzig, 1903. 

 J. S. Macdonald, " The Structure and Function of Nerve Fibres," ' Koy. Soc. Proc.,' B, 



vol. 76, 1905. 



The Influence of Increased Barometric Pressure on Man. — II. 



By Leonard Hill, F.B.S., and M. Greenwood, Jr., M.E.C.S., British 

 Medical Association Besearch Scholar. 



(Beceived October 6, — Bead November 8, 1906.) 



In a previous communication, we gave reasons for thinking that decom- 

 pression symptoms may be avoided by maintaining a steady rate of 

 20 minutes per atmosphere during this process. 



The actual time selected was purely empirical, being based on the statistics 

 of Caisson "Works, Diving Operations, and Laboratory Experiments. It is 

 clear that a more scientific foundation would be obtained if we could determine 

 (1) the rate at which the tissue fluids are saturated with nitrogen ; (2) the 

 rapidity with which dissolved gas escapes during decompression. The most 

 direct method would be to analyse samples of arterial blood under various 

 pressure conditions ; but this is not, unfortunately, practicable in the case of 

 man. Another way is the examination of venous samples under similar 

 circumstances. This plan can be followed, and we hope to communicate 

 some results in another paper, but the technic is difficult and still in need 

 of improvement. A third line of research is the indirect determination of 

 the tissue gases, and this will be discussed in the present communication. 



If a condition of diuresis be produced by drinking considerable amounts 

 of water, the profuse secretion of urine which results will afford some 

 measure of the dissolved tissue fluid gases. We have proceeded in the 

 following way : — The subject of the experiment drinks at least a quart of 

 warm water, and, after an interval of 10 to 15 minutes, enters the pressure 

 chamber, the pressure being then raised a definite amount. Directly the 

 desired pressure has been attained, he empties his bladder. Ten minutes 

 later the bladder is emptied again. Samples of the urine passed are then run 



