612 PRINCIPLES OF GENERAL PHYSIOLOGY 



any more -sugar to alcohol in the absence of oxygen than in its presence (Buchner 

 and Rapp, 1899). It may be held, nevertheless, that yeast is an abnormal 

 organism, produced under the process of repeated selection for a special purpose. 

 In the case of the animal cell, we have already (page 276) seen reason to hold 

 that alcohol is not a normal stage of sugar metabolism. Further, the valerianic 

 acid produced by Ascaris must be a special form of anaerobic metabolism. It is 

 difficult to make any statement as to the characteristic putrefaction products, 

 since the organisms are inactive in the presence of oxygen and we do not know 

 what their metabolism might be in such circumstances. 



. THE OXYGEN CONSUMPTION OF TISSUES 



We have already referred, incidentally, to the requirements of certain tissues 

 as regards oxygen supply, both in rest and in activity. For further data, the 

 essay by Barcroft (1908), together with his book (1914), may be consulted. 



The following numbers may be of interest : 



Xubmaxillary Gland. In the experiments of Barcroft and Piper (1912), the 

 oxygen used in the resting gland amounted to 0-027 c.c. per gram per minute. 

 The results as regards activity have been referred to above (page 342). The 

 consumption went up to 0*089 c.c. in a particular case and continued to be raised 

 for a hundred seconds or more after the flow of saliva has ceased. For the 

 production of 0-3 c.c. of saliva, 0-18 c.c. of oxygen was used over and above that 

 of the resting condition. 



The Kidney. The most recent measurement is that of Neuman (1912). 

 Under ordinary conditions, the oxygen consumption was found to be from 0'026 to 

 0*06 c.c. per gram per minute. Results under stimulation to secretory activity 

 have been given above (page 358). The increase was about four to five times 

 that in rest. 



The Liver. Barcroft and Shore (1912) found that, in cats unfed for thirty 

 six hours, the oxygen consumption amounted to from 0-005 to 0*018 c.c. per gram 

 per minute. In animals fed eighteen hours previously, 0*024 to 0'05 c.c. For 

 the viscera drained by the portal vein, chiefly intestine, the values were 0*008 to 

 0*013 c.c. for the unfed, and 0*011 to 0018 c.c. for fed animals. These facts 

 indicate that the chief metabolism during late digestion is in the liver. 



The Suprarenal Gland. A striking fact about this organ is the rich supply of 

 blood. Neuman (1912) found that a blood pressure of 130 mm. of mercury drives 

 through it 6 to 7 c.c. of blood per gram per minute. This is higher than that of any 

 other organ. Its oxygen consumption is 0*045 c.c. per gram per minute, and is 

 increased threefold during a rise of blood pressure produced by adrenaline. 



The Heart. The chief work on this organ has been done by Rohde (1910) and by 

 Rohde and Nagasaki (1913) on the mammalian heart perfused with Ringer's solution 

 and by Lovatt Evans (1912, 1, and 1914, 1) on the heart-lung preparation perfused 

 with blood. The results will be considered in a later chapter, when dealing with tilt- 

 mechanism of the cardiac contraction. It may be stated here that the oxygen con- 

 sumed in any one contraction varies directly with the maximal tension developed, in 

 accordance with the results of A. V. Hill (page 443) on energy production in skeletal 

 muscle. The oxygen used per minute depends directly on the number of beats ; so 



that, as Rohde expresses it, -^, is a constant for normally beating hearts, where Q 



is the quantity of oxygen consumed per minute, N is the pulse rate, and T the 

 maximum tension. The amount of oxygen consumed per gram weight, according 

 to the results of Evans, is from 0*043 to 0*085 c.c. per minute. 



The Lungs. In the course of the above work, Evans (1912, 1) determined the 

 metabolism of the lung tissue. This is of some importance with regard to certain 

 theories which supposed that a considerable degree of oxidation of metabolic pro- 

 ducts of tissues took place here. It amounts only to 0*015 c.c. per gram per minute, 

 really a low figure. 



The Nerve Centres. Tfre metabolism of the nerve centres has been referred to 



