ON THE ' METABOLIC BALANCE l?HEET ' OF THE INDIVIDUAL TISSUES. 427 



studying the effect of anaerobic and aerobic conditions respectively on the 

 survival life of muscle. Preliminai-y results showed that as certain errors 

 were present in estimations of lactic acid, made by earlier observers, the 

 more fundamental experiments had to be repeated. These erroi'S are due 

 to the fact that the preliminary treatment of the muscle produces so much 

 more effect upon the content of lactic acid than has been suspected. 

 Chopping up the iliuscles may by itself increase the amount of acid very 

 largely, and when intact muscles are placed under alcohol the surface 

 stimulus involved may increase it tenfold. Such errors being eliminated, 

 the following new data have been obtained. The surviving muscle, con- 

 taining lactic acid due to fatigue, has the power of getting rid of this acid 

 during the recovery of activity which occurs on exposure to an atmosphere 

 of pure oxygen. The rate of this disappearance of acid and the effect of 

 various factors upon it have been studied. The removal depends upon 

 the integrity of the architecture of the muscle fibre. That the removal is 

 due to simple oxidation is not yet certain. 



The curve of lactic-acid production in resting muscle has been fully 

 studied, and the results, together with the proof that under certain con- 

 ditions much larger quantities of acid can be produced than previous 

 experimentation had suggested, indicate that the metabolite either arises 

 from a precursor present in much larger quantity than the preexisting 

 carbohydrate or (an important alternative) the muscle during recovei-y 

 from fatigue, ike, syntherises the lactic acid into a complex which may 

 again break down. An endeavour to discriminate between these possi- 

 bilities will form the basis for future work. 



Some preliminary experiments have been performed by Barcroft, 

 Mottram, Stansfeld, and Miss Tweedie on the amount of oxygen used per 

 gramme of skeletal muscle. These experiments yielded a value much 

 lower than what has been observed in many other organs. 



An example may be given. In a dog (weight 17 kilos.) the muscles 

 of the right-hand leg weighed 2,980 grammes. The blood-flow through the 

 limb was 150 c.c. per minute. Each 100 c.c. of blood gained 9-2 c.c. of 

 CO.j, and lost 9-1 c.c. of Oj. The actual amount of COo gained by the 

 blood and oxygen lost per gramme of muscle per minute was therefore 

 CO2 = '0046 O2 = '00455 c.c. This muscle was at rest in the sense that 

 the lumbar and sacral regions of the cord were destroyed. The anaesthesia 

 (A.C.E.) was light. 



II. The researches already reported (see 1905 report) upon the 

 mammalian kidney have been extended to that organ in the frog. The 

 chief results which have been obtained are as follows : — 



(1) When the frog's kidney is perfused through the renal portal 

 system with oxygenated or aerated saline solution the amount of oxygen 

 used up is markedly less than would be used by the same weight of 

 mammalian kidney. 



(2) Under these circumstances there is an increase in the oxygen con- 

 sumption when the perfusing solution contains caffeine (two experiments), 

 urea O'l per cent, (one experiment), sodium sulphate (three experiments) ; 

 whilst it was greatly reduced by 4 per cent, urea (one experiment) and 

 abolished by 5 per cent, urea (one experiment). 



(3) When the same kidney is perfused at different times through the 

 aorta, and through the renal portal system, there is a greater consumption 

 of oxygen in the former case than in the latter (double to treble in four 

 experiments). 



