138 APPENDIX II. 



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 centuries this doctrine sank into oblivion ; 

 and it is only within the last two years that it has 

 been again advanced, chiefly by Haidenhain,* 

 Traube, and, to a limited extent, by Donders.f 



Experimental evidence was, however, still want- 

 ing to give permanent vitality to the resuscitated 

 doctrine; for although the laborious and remarkable 

 investigations of VoitJ 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 

 sufficiently conclusive character has been supplied 

 by a happily conceived experiment undertaken by 

 Fick and Wislicenus in the autumn of 1865, 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, viz., the 

 amount of actual energy generated by the oxidation 



* Mechanische Leistung Wdrmeentwickelung und Stoffum- 

 satz lei der Muskdthatigleeit, 1864. 



t 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. 



t Untersuchungen uber den Einfluss des Kochsalzes, des 

 Kaffee's und der Muskel-lewegungen auf den Sto/wedisel, 

 p. 150, Munich, 1860. 



Phil Trans., 1861, p. 747. 



