RESPIRATION 197 



nearly as efficient as normal blood. This is due to the fact that, as 

 already explained in Chapter V, the haemoglobin and other pro- 

 teins play the essential part in the actual conveyance of CO2 from 

 the tissues to the lungs, and can still play this part in spite of what, 

 in a physiological sense, is extreme acidosis. 



The experiments were practically a replica in man of the ex- 

 periments of Geppert and Zuntz on muscular activity in dogs 

 (Chapter I). In discussing these experiments Priestley and I were 

 not aware that a very great diminution of the CO2 content of the 

 blood may be caused by acidosis without any serious diminution 

 in the capacity of the blood for conveying CO2 from the tissues to 

 the lungs. The discovery made in 19 14 by Christiansen, Douglas, 

 and myself has greatly altered the previously existing ideas as to 

 the conveyance of CO2 from the tissues. 



The comparatively rapid recovery of the blood after the flood- 

 ing of the body with lactic acid was evidently due to the fact that 

 lactic acid was rapidly oxidized before the slight acidosis actually 

 produced had time to cause any considerable extra excretion of 

 acid by the kidneys, or formation of ammonia by the liver. Had 

 the acidosis been produced by a mineral acid it would probably 

 have taken far longer to pass off. 



Disturbance of the blood reaction may be artificially produced 

 by the ingestion of acids or alkalies, or even, to a slight extent, by 

 varying the character of the diet. It requires a very large amount 

 of acid or alkali to produce any considerable disturbance. This is 

 partly due to the abundance of buffer substances in the body, but 

 still more to the effective means (variations in lung ventilation, 

 ammonia formation, and excretion of acid or alkali by the kid- 

 neys) which the body possesses of active defence against dis- 

 turbance of reaction. If the administration of acids or alkalies is 

 used medicinally as a means of assistance in the regulation of the 

 blood reaction, the large doses required must be borne in mind. 

 Small doses cannot but be practically useless. The amelioration of 

 the physiological symptoms of acidosis or alkalosis will form the 

 safest guide to what is required; but it is evidently very important 

 not to mistake alkalosis for acidosis, or the hyperpnoea of acidosis 

 for the abnormal breathing caused by anoxaemia or an exhausted 

 or "neurasthenic" respiratory center. There are no short cuts to 

 decisions on such a subject. A physician must be a real physician, 

 and must have learned to be one by study of how the living body 

 behaves — of what its <Awrts is, to use the old expression of Hip- 

 pocrates. 



