ON THE SOTJRCE OF MUSCULAR POWER. 251 



Mayow,* distinctly stated that for the production of muscular motion 

 two things are necessary — the conveyance of combustible substances 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 com- 

 bustion is supported by the oxygen of the air, and that this gas is 

 absorbed in the lungs by the blood, and is absolutely necessary for 

 muscular activity. 



For two decades this doctrine sank into oblivion ; and it is only 

 within the last two years that it has been again advanced, chiefly by 

 Haidenhain,f Traube, and, to a limited extent, by Bonders. J 



Experimental evidence was, however, still wanting to give perma- 

 nent vitality to the resuscitated doctrine ; for although the laborious 

 and remarkable. investigations of Voit|| and of Edward Smith§ point 

 unmistakably in the direction of Mayow and Mayer's hypothesis, yet 

 the results of these physiologists were not sufficiently conclusive to 

 render the opposite view untenable. This want of data of a suffi- 

 ciently conclusive character has been supplied by a happily conceived 

 experiment undertaken by Fick and "Wislicenus in the autumn of last 

 year, and described in the 'Philosophical Magazine,' vol, xxxi. p. 485. 

 In the application of these data, however, to the problem now under 

 consideration, one important link was found to be wanting, vis:, the 

 amount of actual energy generated by the oxidation of a given weight 

 of muscle in the human body.. Fick and Wislicenus refer to this 

 missing link in the following words : — " The question now arises 

 what quantity of heat is generated when muscle is burnt to the pro- 

 ducts in which its constituent elements leave the human body through 

 the lungs and kidneys ? At present, unfortunately, there are not the 

 experimental data required to give an accurate answer to this impor- 



* ' De Motu musculari,' 1681. Majow was born ia 1645, and died 1679. 



f ' Mechanische Leistung Warmeentwickelung uod StofiFumsatz bei der Mus- 

 kelthatigkeit,' 1864. 



X As this is passing through the press, the speaker has become aware that 

 Messrs. Lawes and Gilbert advocated this doctrine in 1852, and repeatedly since ; 

 their opinions being founded upon experiments on the feeding of cattle. 



II ' Untersuchungen uber den Einfluss des Kochsalzes, des Kafifees und der 

 Muskel-bewegungen auf den Stoffwechsel,' p. 150. Munich, 1860. 



§ ' Phil Trans.,' 1861, p. HI. 



