[29]. Heidenhain, op. cit. Also by Fick, Untersuchungen über Muskel-arbeit, Basel, 1867. Compare also “Nature,” i, 159, Dec. 9, 1869.
[30]. Du Bois-Reymond, Emil, On the time required for the transmission of volition and sensation through the nerves, Proc. Roy. Inst. Also in Appendix to Bence Jones’s Croonian lectures.
[31]. Marshall, op. cit., p. 227.
[32]. Melloni, Ann. Ch. Phys., xlviii, 198.
See also Nobili, Bibl. Univ., xliv, 225, 1830; lvii, 1, 1834.
[33]. The apparatus employed is illustrated and fully described in Brown-Sequard’s Archives de Physiologie, i, 498, June, 1868. By it the 1-4000th of a degree Centigrade may be indicated.
[34]. Lombard, J. S., New York Medical Journal, v, 198, June, 1867. [A part of these facts were communicated to me directly by their discoverer.]
[35]. Wood, L. H., On the influence of Mental activity on the Excretion of Phosphoric acid by the Kidneys. Proceedings Connecticut Medical Society for 1869, p. 197.
[36]. On this question of vital force, see Liebig, Animal Chemistry. “The increase of mass in a plant is determined by the occurrence of a decomposition which takes place in certain parts of the plant under the influence of light and heat.”
“The modern science of Physiology has left the track of Aristotle. To the eternal advantage of science, and to the benefit of mankind it no longer invents a horror vacui, a quinta essentia, in order to furnish credulous hearers with solutions and explanations of phenomena, whose true connection with others, whose ultimate cause is still unknown.”