PREFACE
The title to these pages may, perhaps, seem rather obscure, on account of the various senses in which the word molecular has at different times been employed. I do not, however, know any better term by which to express all that refers to the attraction which exists amongst the particles of matter at insensible distances.
The word chemical is restricted to expressing what relates to the composition of bodies, and does not include properties, such as solidity and fluidity, which are called physical; nor some of the processes that we call vital, such as the formation of fibers and cells. It is especially desirable to have a general term to include what is understood by the words physical, chemical, and vital, in order to avoid the disputes respecting these two latter words, (disputes in which we see such authors as Humboldt, Liebig, and Alison engaged,) and the need less antagonism in which these words are sometimes placed towards each other.
All changes of composition whatever, whether occurring in a test-tube, or in the living brain, are properly included amongst chemical changes; and all that takes place in living structures has a right to be called vital, whether it differs from what occurs elsewhere or not. Thus, whilst the terms chemical and vital have each a separate signification, they have a certain ground in common, since changes of composition in living beings are at once both chemical and vital, and belong to both chemistry and physiology; just as fossil animals belong to both the mineral and animal kingdoms, and to the sciences of geology and zoology at the same time. To dispute whether the formation of urea or cholesterine is a chemical or vital process, is as useless as it would be to dispute whether a fossil ichthyosaurus is a mineral or an animal, and whether it belongs to geology or zoology.
I beg the reader to remember that the term oration proceeds from the laws of the Medical Society, and not from any claim of mine to be considered an orator.
March 26, 1853.