

APPENDIX II. 137 



itself in 8 days, and the ventricles of the heart in 

 2J days. After endeavouring to prove by physi- 

 ological arguments that not one per cent, of the 

 oxygen absorbed in the lungs could possibly come 

 into contact with the substance of the muscles, 

 Mayer says : " The fire-place in which this com- 

 bustion goes on is the interior of the blood-vessels, 

 the blood however a slowly-burning liquid is the 

 oil in the flame of life. . . . Just as a plant-leaf 

 transforms a given mechanical effect, light, into 

 another force, chemical difference, so does the muscle 

 produce mechanical work at the cost of the chemical 

 difference Consumed in its capillaries. Heat can 

 neither replace the sun's rays for the plant, nor the 

 chemical process in the animal : every act of motion 

 in an animal is attended by the consumption of 

 oxygen and the production of carbonic acid and 

 water ; every muscle to which atmospheric oxygen 

 does not gain access ceases to perform its functions." 

 But Mayer was not the first to conceive this view 

 of muscular action. Nearly 200 years ago, a Bath 

 physician, Dr. John Mayow,* distinctly stated that 

 for the production of muscular motion two things 

 are necessary the conveyance of combustible sub- 

 stances to the muscle by the blood, and the access of 

 oxygen by respiration. He concluded that the chief 

 combustible substance so used was fat. A century 

 before Priestley isolated oxygen, Mayow was aware 

 of its existence in the air, in nitre, and in nitric 

 acid ; he knew that combustion is supported by the 



* De Motu muscular i, 1681. Mayow was bora in 1645, 

 and died 1679. 



