606 PRINCIPLES OF GENERAL PHYSIOLOGY 



force " (that is, diminished in volume) " by the breathing of animals very much in the same 

 way as by the burning of flame. And indeed we must believe that animals and fire draw 

 particles of the same kind from the air, as is further confirmed by the following experiment" 

 (p. 75). 



On p. 151 : " Quemadmodum sanguinis fermentationem, ita etiam illius incalescentiam a 

 particulis nitro aereis cum particulis cruoris salino-sulphureis exsestuantibus, oriri existimo." 

 "Just as the fermentation of the blood, so also its heat arises I think from the effervescence 

 of nitro-aerial particles with salino-sulphureous particles of the blood " (p. 104). 



On p. 152: " Quanquam calor iste in animalibus, per exercitia violenta excitatus, etiam 

 ab effervescentia particularum nitro-aerearum et salino-sulphurearum in partibus motricibus 

 orta, partim provenit, ut alibi ostendetur." "Nevertheless, the heat excited in animals by 

 violent exercise is in part also due to the effervescence, originating in the motor parts them- 

 selves, between the nitro-aerial particles and the salino-sulphureous particles, as will be pointed 

 out elsewhere. " 



With regard to the two last passages, we must remember that, as is evident from other 

 parts of the book, "salino-sulphureous particles" are what we now call combustible substances. 

 It appears from the last passage that Mayow rightly held that combustion went on in the 

 muscles themselves, although he was incorrect in his statement that it took place in the blood 

 also. I have ventured to put this passage into slightly different words from those used by the 

 translator of the " Alembic Club." It is clear that " effervescentia " agrees with " orta," that 

 is, it is the "effervescence" (combustion) that arises in the muscle, not merely the salino- 

 sulphureous particles, which would escape into the blood and be burnt there. This is a point 

 of some importance, since it was held even by Lavoisier that the combustions take place in 

 the lungs, so that Mayow was in advance of his successors. A portrait of Mayow is given in 

 Fig. 184, being that placed at the front of his book. 



The importance of Mayow's discovery was lost sight of in the rapid development 

 of the phlogiston doctrine and oxygen was rediscovered by Priestley (1774), who 

 called it " dephlogisticated air." As we have seen, Priestley also showed that air, 

 which had been "spoilt" by animal respiration, was restored by green plants. 

 Priestley's portrait is given in Fig. 185 and a copy of the frontispiece to his book 

 in Fig. 186. As is well known, the doctrine of phlogiston was overthrown by 

 Lavoisier (1770, etc.), who showed the true nature of oxidation and gave the name 

 "oxygen" to Priestley's "dephlogisticated air." With Lavoisier, modern chemistry 

 with its use of the balance commences. It has been stated that his discovery of 

 oxygen was suggested by the account given to him by Priestley. However this 

 may be, there is no doubt that he was the first, after Mayow, who saw the 

 phenomena in their real aspect. A portrait of Lavoisier with his wife will be 

 found in Fig. 187. The product of combustion in living beings was not known to 

 Mayow. It was shown by Black (1755) to be something quite different from 

 common air, and was called by him, " fixed air," but its true nature as an oxide of 

 carbon was discovered by Lavoisier. A sketch by Madame Lavoisier of an 

 experiment on respiratory exchange in work, performed in Lavoisier's laboratory, 

 is reproduced in Fig. 188. Madame Lavoisier is taking notes. 



As we commenced the study of the subject with the oxidation processes in the 

 cell, it will be most appropriate to take in order the stages backwards from the cell 

 to the lungs and the outer atmosphere. 



THE STORAGE OF OXYGEN 



We saw in the preceding chapter how the processes of oxidation and reduction 

 in the cell are under the control of enzymes and the part played by peroxides 

 therein. Thus, at a given moment, there will be a certain amount of available 

 oxygen present in the cell as peroxide. But this must be extremely small. 



At one time, it was generally thought that the cell contained a store of " intra- 

 molecular" oxygen in some loosely combined form. In our first chapter we 

 discussed the more modern form of this belief, in the guise of " biogen " molecules, 

 supposed to contain loosely combined oxygen in one side chain, together with 

 combustible substance in another, so that cell oxidations might proceed without 

 immediate supply of fresh oxygen. Since this view is still held in some quarters, 

 occasionally in a more or less modified form, it is important to give further 

 evidence bearing upon it. 



Of course, a very small amount of oxygen may exist in the cell fluids in 

 ordinary solution, and the time taken to consume this would vary with the rate of 



