APPENDIX II. 135 



from the albumen of the blood ; all the albumen of 

 the blood is derived from the plastic or sanguineous 

 constituents of the food, whether animal or vege- 

 table. It is clear, therefore, that the plastic con- 

 stituents 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 organs of sense, thought, and 

 motion." And again, at page 374, he says : " The 

 sulphurized and nitrogenous constituents of food 

 determine the continuance of the manifestations of 

 force; the non-nitrogenous serve to produce heat. 

 The former are the builders of organs and organized 

 structures, and the producers of force ; the latter 

 support 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 considerations 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 

 transformation 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 

 considering the contraction of a muscle due to a 

 disintegration of its particles, and its relaxation to 



* Tetanus eine Physiologische Studie. Leipzig. 1865. 



