ACIDOSIS 55 



of material then available by L. J. Henderson in 1909, and has been con< 

 firmed by Lundsgaard(a) (1912) and other subsequent investigators, utiliz- 

 ing the gas chain method. Parsons (1917) working with especial precau- 

 tions showed that the actual pH value determined is that of the plasma, and 

 that the pH of venous blood in a given individual is normally only 0.02 

 below that of arterial blood. The maximum normal range of variation of 

 blood reaction in different individuals appears to be indicated by pH 7.3 

 to 7.5. It is possible that when errors of technique are more completely 

 excluded this range will become still narrower. 



Under extreme abnormal conditions the pH may fall as low as 6.95, but 

 at or above this point it is probable that coma occurs, and, from the fact 

 that lower pH values have not been observed, it is doubtful that further 

 decrease is compatible with Jife. 



This was the lowest point observed by Hasselbalch and Lundsgaard(&y 

 (1912) in rabbits killed by prolonged breathing of air with contained CO 2 . 

 It is also the lowest point observed by Van Slyke, Austin, and Cullen 

 (1920) in experiments on etherized dogs, A pH of 6.95 was in one in- 

 stance determined electrometrically by Cullen (unpublished) in the blood 

 of a nephritic man in coma a few hours before death. 



By voluntary deep breathing, on the other hand, carbonic acid may be 

 blown off until the blood alkalinity rises to a pH of 7.7 or 7.8 (Daviee, 

 Haldane, and Kennaway, 1920; Collip and Backus, 1920), at which point, 

 however, symptoms of tetany appear (Grant and Goldman, 1920). It 

 therefore appears that the extreme range of reaction compatible with life 

 lies approximately between pH 6.95 and pH 7.80 and that the normal 

 range is within limits no greater than pH 7.3 to 7.5, and possibly somewhat 

 narrower. 



Concerning the pH of the body fluids other than blood plasma our 

 knowledge is limited, but such as it is indicates that these fluids approxi- 

 mate the blood plasma closely in their reaction. (By body fluids are meant 

 the fluids within the body proper, such as lymph, cerebrospinal fluid, trans- 

 udates, exudates, but not secretions such as gastric juice or urine). Par- 

 sons and Shearer (1920) .found in the cerebrospinal fluid a pH normal 

 for blood plasma. 



In the body fluids, data, to which we refer above, have shown 

 that the bicarbonate is normal for blood plasma. As there is reason 

 to believe that the CO 2 tension in these fluids approximates that of 

 the arterial blood (Haggard and Henderson, 1919) it is probable 

 that a bicarbonate concentration normal for blood plasma indicates 



"RTTOO 

 also a ratio, and therefore, as will be shown presently, a pH, 



normal for blood plasma. 



