, ON THE SOURCE OF MUSCULAR POWER. 219 



This doctrine, first promulgated, the speaker believed, hy Liebig, 

 occupies a prominent position in that philosopher's justly celebrated 

 ' Chemico- Physiological Essays.' 



In his work entitled 'Die organische Chemie in ihrer Anwendung 

 auf Physiologic und Pathologic, Braunschweig, 1842,' Liebig says, 

 ** All experience teaches that there is only one source of mechanical 

 power in the organism, and this source is the transformation of the 

 living parts of the body into lifeless compounds. . . . This trans- 

 formation occurs in consequence of the combination of oxygen with 

 the substance of the living parts of the body." And again, in his 

 ' Letters on Chemistry, 1851/ p. 366, referring to these living parts 

 of the body, he says, " All these organized tissues, all the parts 

 ■which in any way manifest force in the body are derived from the al- 

 bumen of the blood ; all the albumen of the blood is derived from 

 the plastic or sanguineous constituents of the food, whether animal 

 or vegetable. It is clear, therefore, that the plastic constituents of 

 food, the ultimate source of which is the vegetable kingdom, are the 

 conditions essential to all production or manifestation of force, to all 

 these effects which the animal organism produces by means of its or- 

 gans of sense, thought, and motion." And again, at page 374, he 

 says, " The sulphurized and nitrogenous constituents of food deter- 

 mine the continuance of the manifestations of force ; the non-nitro- 

 genous serve to produce heat. The former are the builders of organs 

 and organized structures, and the producers of force ; the latter sup" 

 port the respiratory process, they are materials for respiration." 



This doctrine has since been treated as an almost self-evident truth 

 in most physiological text- books; it has been quite recently supported 

 by Ranke ; * and, in his lecture * On the Food of Man in relation to 

 his Useful "Work, 1865,' Playfair says, page 37, " From the conside- 

 rations which have preceded, we consider Liebig amply justified in 

 viewing the non-nitrogenous portions of food as mere heat-givers. . 

 . . While we have been led to the conclusion that the transforma- 

 tion of the tissues is the source of dynamical power in the animal." 

 At page 30 he also says, "I agree with Draper and others in consi- 

 dering the contraction of a muscle due to a disintegration of its par- 

 ticle^, and its relaxation to their restoration. . . . All these 

 facts prove that transformation of the muscle through the agency of 



*' Tetanus eine Physiologische Studie.' Leipzig. 1865. 



