May I, 19 19] 



NATURE 



163 



he regards as quite well-marked "acidosis." He 

 defines acidosis, not as a state in which the 

 hydrog-en-ion concentration of the blood and 

 tissues is abnormally increased, but as one in 

 which the reserve of fixed alkali in the body is 

 depleted. This depletion is shown by the fact that, 

 whereas in a normal individual it only requires a 

 small dose of sodium bicarbonate to make the 

 urine alkaline, it requires a very large dose in the 

 case of a patient suffering from acidosis. 



The evidence which Dr. Sellards adduces to 

 illustrate the soundness of this test for acidosis 

 is very interesting and, in the main, new. Much 

 of this evidence is from observations which he 

 made in the Philippines in treating kidney inflam- 

 I mation in cholera. Acidosis may be due to 

 i abnormal flooding of the body with organic acids, 

 f as in diabetic coma, or to failure on the part of 

 the kidneys to excrete acid, as in kidney inflamma- 

 tion. In either case the test proposed by Dr. 

 Sellards indicates the condition. But the whole 

 subject becomes much clearer if it is recognised 

 that in serious acidosis there is an actual increase 

 in the hydrogen-ion concentration of the blood, 

 and that of this increase the increased breathing 

 is by far the most direct sign. It appears to be 

 the untrustworthiness of direct means of measur- 

 ing small differences in hydrogen-ion concentra- 

 tion that has led some writers in this country to 

 deny that dangerous acidosis exists at all in such 

 conditions as diabetic coma or kidney disease, 

 although both the greatly increased breathing and 

 the favourable effect on the symptoms of large 

 doses of sodium bicarbonate indicate the existence 

 of what is, physiologically speaking, an extreme 

 state of acidosis. 



The confusion is rendered still greater by failure 

 to distinguish primary acidosis due to flooding 

 of the body with acid from the secondary acidosis 

 which is an adaptive physiological response to 

 lack of oxygen, and leads to increased ventilation 

 of the lungs and, consequently, increased supply 

 of oxygen to the blood. This form of acidosis is 

 met with typically at high altitudes and in various 

 conditions, such as poisoning by irritant gases, 

 where the free supply of oxygen to the body is 

 interfered with. Here the acidosis is brought 

 about by diminution in the amount of fixed alkali 

 or "alkaline reserve " in the blood, with the result 

 that the breathing is increased. There is no 

 directly measurable increase in hydrogen-ion con- 

 centration of the blood, nor, in view of what has 

 already been said, could this be expected ; but the 

 increased breathing is, nevertheless, good evidence 

 of the existence of an increase. The diminution 

 in alkaline reserve in the blood is easily detected, 

 either by titration or by a diminution in the 

 capacity of the blood for combining with CO, ; 

 and the latter method, particularly in the form 

 given to it by Van Slyke, has been extensively 

 used during the last year or two. The acidosis 

 detected in this indirect way has, however, fre- 



Iquently been interpreted as in itself a symptom to 

 be combated by alkalis, when it is in reality an 

 advantageous compensatory reaction. For- 

 NO. 2583, VOL. 10.3] 



tunately, the body can usually dispose of even 

 large quantities of alkaline medicaments adminis- 

 tered through this misunderstanding. Dr. Sel- 

 lards's test for acidosis would exclude a com- 

 pensatory acidosis, but would also lead to a com- 

 pensatory acidosis being missed, and perhaps, as 

 a consequence, to the cause of the compensatory 

 acidosis being overlooked. 



To interpret the significance of increased breath- 

 ing, diminished alkaline reserve in the blood, or 

 any of the other symptoms which usually accom- 

 pany acidosis, it is necessary to take the whole of 

 any existing abnormal physiological conditions 

 into account, just as in interpreting the signi- 

 ficance of any one of the usual physical signs of 

 disease it is necessary to consider the whole of 

 the symptoms and their course. The confusion 

 which exists at present on the subject of acidosis 

 is largely due to neglect of this principle. Per- 

 haps this confusion is rendered most evident by 

 the quite recent discovery by Yandell Henderson 

 that when an animal is dying of "alkalosis," pro- 

 duced by withdrawing carbonic acid from the body 

 by excessive artificial respiration, the alkaline 

 reserve in the blood is greatly diminished in a 

 physiological effort of the body to preserve the 

 normal reaction ; and, conversely, that when an 

 animal is suffering from extreme acidosis owing 

 to a great excess of COj in the inspired air, the 

 alkaline reserve of the blood is greatly increased 

 in a corresponding compensatory effort. A 

 diminution in alkaline reserve of the blood is thus 

 not by itself a certain index of acidosis, or of 

 whether or not an acidosis, if it exists, is harmful. 



J. S. Haldane. 



TROPISMS. 



Forced Movements, Tropisms, and Animal Con- 

 duct. By Prof. Jacques Loeb. Pp. 209. (Phila- 

 delphia and London: J. B. Lippincott Co., 

 1918.) Price I05. 6d. net. 



A PROLIFIC investigator does a great service 

 to his brethren when, without waiting to 

 write an elaborate treatise, he collects the gist of 

 some considerable f>ortion of his work into a book ; 

 and if the book be a small one, so much the 

 better. This Prof. Loeb has now done, and we 

 are immen.sely obliged to him. What is more, his 

 volume is but the first of a series, by American 

 writers, all dealing with the wide field of experi- 

 mental biology, a field in which we at home have 

 done comparatively little, but in which American 

 biologists have greatly distinguished themselves. 

 Among the promised monographs are one by Prof. 

 Morgan on "Chromosomes and Heredity"; 

 another, by Dr. Jennings, on " Pure Line Inherit- 

 ance " ; a third, by Dr. T. B. Robertson, on "The 

 Chemittil Basis of Growth"; and a fourth, by 

 Prof. Osterhout, on " Permeability and Conduc- 

 tivity of Living Tissues." In every case (and 

 there are many more besides these) the author has 

 won, and more than won, his right to be heard, 

 and in every case also we feel the need of an 

 authoritative guide to the subject in question. 



