94 The Functions of the Blood. 



is effected, we are justified in inferring that it is by the direct 

 agency of the corpuscles. There is on this view no ground for 

 the assumption that either force or heat is due exclusively to the 

 oxidation of one or the other class of organic compounds. 

 Both are oxidized, and one is as likely as the other to be the 

 motive power. Even the muscle itself, inasmuch as it is finally 

 oxidized in the blood, may give rise to muscular work, and we 

 must therefore conclude that Traube's hypothesis is as much 

 an over- statement on the one side as Liebig's was on the 

 other. 



The changes effected by the blood in the exercise of its 

 functions are subject, to a most remarkable extent, to the 

 control of the nerves ; and little as we know of this the most 

 obscure region of physiology, we cannot avoid the conclusion 

 that they are directly concerned in the transformation of 

 chemical force into mechanical effect. The muscular currents 

 of electricity, which have been so carefully studied by Du Bois- 

 Heymond, Helmholtz, Heidenhain, and many others, are, no 

 doubt, closely connected with this conversion ; but I will 

 abstain from speculations which are apt to degenerate into bare 

 guesses. Dim for eshado wings of great discoveries lie before 

 us, and it is better, after clearly stating to ourselves the truths 

 already established, or made probable, to wait with humility, 

 watching till diligent and patient search shall have been 

 rewarded with fresh unveilings. If we can clear a point or 

 two in the intricate forest of knowledge which lies before us, 

 we shall have done truer work than by any amount of 

 speculation. 



