414 EEIL. HUMBOLDT. J. LIEBIG. [BOOK I. 



Reil and On the other hand, Reil and his brilliant pupil 



von Madai. von Madai 1 avoided even the semblance of a vital or 

 irritable principle by referring to the structure and chemi co-physical 

 changes of living matter all the peculiar phenomena of life. As to 

 the nature of the changes Reil was not explicit ; and, although von 

 Madai adopted provisionally the term phlogistic processes, because 

 carbon and oxygen play so important a part in them, it was with a 

 wise reservation as to their exact nature and method (loc. cit. p. 101). 



It was, however, Humboldt 2 who first denied with 

 Humboldt. . , , . ,, ' , . . ,, 



special emphasis the exclusive importance of oxygen in 



the vital processes. Many observations had disclosed to him vital 

 processes in which oxygen takes none but a subordinate part. To 

 speak of life as an oxidation is to take a one-sided and distorted view 

 of vital phenomena. Oxygen in his opinion is a most important 

 stimulus, but not the common basis, of irritability. It is true that 

 many phlogistic processes occur in the performance of vital functions : 

 but how many other chemical decompositions go forward which do 

 not so much express the affinity of oxygen for phosphorus, azote, 

 hydrogen and carbon, as the affinities of these for one another ? 

 Thus physiology became accustomed to the absence of a particular 

 contractile or irritable principle. First its office and dignity were 

 conferred upon oxygen, and then oxygen was reduced to the rank 

 and privileges of a common chemical element. 



. The doctrine of vital force in muscular action by no 



means at once gave place to the views of the physico- 

 chemical school. It remained indeed the prevalent doctrine until 

 the time of Baron Liebig 8 , who attempted to bring it into rela- 

 tion with the most recent discoveries of Physiological Chemistry. 

 The vital force, resident in animals and plants, finds its scope of 

 action in the presence of a certain structure and organization of parts. 

 It is governed by laws in harmony with the universal laws of resistance 

 and motion ; nevertheless it is independent of the matter in which 

 vitality is manifested. It is this vital force which keeps living matter 

 from decomposition even in the presence of oxygen, which determines 

 its growth, and which also causes the movements of animals. Besides 

 a special organization of substance, a certain temperature and a 

 constant supply of food are indispensable conditions of its activity. 

 A muscle therefore is an organ endowed, by virtue of its vital proper- 

 ties, with certain powers of self-preservation, growth and motion. 

 While it is at rest, and exposed to the influence of oxygenated blood, 

 the vital force is absorbed in restraining the natural tendencies to 



1 J. C. Eeil, "Ueber die Lebenskraft," Arch, fiir die Physiologic (Eeil), Vol. i. Heft i. 

 p. 8. 1796. D. von Madai, "Ueber die Wirkungsart der Eeize und der thierischen 

 Organe." Ibid., Vol. i. Heft iii. p. 68. 1796. 



2 Al. von Humboldt, Versuche it. die gereizte Muskel- u. Nervenfaser. Vol. n. 

 p. 106 et seq. 



3 J. Liebig, Animal Chemistry, or Organic Chemistry in its applications to 

 Physiology and Pathology. Translated by W. Gregory. London, 1842. 



