RESPIRATION 1 73 



of the most rapid and effective method of all — varying excretion 

 of carbonic acid by the breathing — remained hidden till quite 

 recently, although Walter's experiments showed that there is not 

 only a great increase in the breathing, but the amount of carbonic 

 acid present in the arterial blood is reduced in extreme case to 

 about a twelfth of the normal. 



It was discovered by von Jaksch^ in 1882 that where acetone 

 is present in the urine, as in bad cases of diabetes, verging on 

 coma, or actually comatose, considerable quantities of aceto- 

 acetic acid are also present; and soon afterwards Minkowski* 

 found that oxybutyric acid, a closely allied substance, is likewise 

 present. The excretion of ammonia had already been shown to be 

 greatly increased, as well as the depth of the breathing and the 

 acidity of the urine, just as in acid poisoning; and indeed it was 

 this that led Minkowski, and Stadelmann before him, to the 

 search for organic acids. Thus all the symptoms point to acid 

 poisoning by the acids mentioned. Shortly after Priestley and I 

 introduced our method of investigating alveolar air, Pembrey, 

 Beddard, and Spriggs investigated the alveolar air in cases of 

 diabetic coma at Guy's Hospital,^ and found the alveolar COg 

 percentage as low as 1. 1 per cent. It went up and down as 

 the patient emerged from or relapsed into coma; and the ad- 

 ministration of sodium bicarbonate warded off the attacks of 

 coma, and at the same time kept the alveolar CO2 percentage from 

 falling. Investigation of the alveolar CO2 pressure is now a well- 

 recognized clinical method for estimating the gravity of symptoms 

 in diabetic coma and other states of "acidosis," as well as for 

 judging of the effects of treatment. 



For a long time the degree of alkalinity of the blood was judged 

 from the amount of acid which has to be added to a given volume 

 of it or its serum before an indicator, such as litmus, gives the tint 

 indicative of neutrality. By this method it was found that the 

 blood in acid poisoning or diabetic coma is less alkaline than 

 usual; and ail sorts of similar supposed "acidoses" have been dis- 

 covered, although the signs of physiological response to the pres- 

 ence in the body of too much acid might be more or less absent or 

 even contradictory. A few years ago, however, it became evident 

 that the amount of acid required for neutralization is no reliable 



*Von Jaksch, Berichte der deutschen Chem. Gesellsch., p. 1496, 1882. 



* Minkowski, Arch. f. exfer. Pathol. «. Pharmak., XVIII, pp. 35 and 147, 

 1884. 



' Beddard, Pembrey, and Spriggs, Journ. of Physiol., XXXI, Proc. Physiol. Soc, 

 p. xliv, 1904; also XXXVII, p. xxxix, 1908. 



