670 THEORY OF SECRETION AND NUTRITION. 



who observes, that " perhaps an imponderable 

 fluid, resembling galvanic electricity, is gene- 

 rated in the nerves, which causes changes in the 

 blood, passes through the delicate net work of 

 the glands, and renders them capable of secre- 

 ting, as supposed by Wollaston, Berzelius, Brodie, 

 Philip, and others." (Comparative Physiology, 

 p. 207.) And so far has Dr. South wood Smith 

 been fettered by this obscure hypothesis, that in 

 his excellent work on the Philosophy of Health, 

 he represents " the repulsive power of the blood 

 on which its fluidity depends, as a vital endow- 

 ment, derived, probably, from the organic nerves, 

 so abundantly distributed to the coats of the blood 

 vessels; " while in another place he maintains that 

 " secretion is effected by means of the electric 

 fluid, conveyed to the different organs by the 

 ganglionic nerves." And although he admits, 

 that the temperature of arterial is somewhat 

 higher than that of venous blood, he observes 

 that the difference is so slight, that in the general 

 theory of animal heat it may be disregarded. 

 (Vol. i. p. 347. Vol. ii. pp. 147213326.) 



Is it then possible that physiologists are in doubt 

 whether the fluidity of the blood is owing to the 

 same cause which determines the fluidity of the 

 ocean ? Or is it possible that the Author of Nature 

 would have ordained that the temperature of ar- 

 terial should be higher than that of venous blood, 

 if the difference were not essential to the well 



