Page:The Harveian oration - delivered at the Royal College of Physicians, London, June 24, 1870 (IA b22307643).pdf/29

 of the ascent to be made; still we must be- ware of accepting any conclusions as final. As I had to remark upon chemistry, that when it reaches the confines of organization, it probably ceases in our living tissues under that form, to appear under some higher correlative-so, no doubt, the same may be said of those molecular conditions with which we are now becoming ac- quainted. The investigation of the reac- tions of colloids is doing for organic tissues and functions what chemistry has done for elements and elementary composition; but how far the explanations thus afforded extend can be determined only by the further progress of knowledge. Whether we are justified in speaking of muscle and nerve as if they had any relation to mere colloid substances, or whether by a knowledge of these we approach nearer to an explanation of nerve force and its trans- mission, or to the contraction of muscle, is at least doubtful; for, notwithstanding the admitted instability of homogeneous sub- stances of complex composition, and the