During the busy years of my professional career, I had snatched leisure for some professional treatises, which had made more or less sensation, and one of them, entitled "The Vital Principle; its Waste and Supply," had gained a wide circulation among the general public.

This last treatise contained the results of certain experiments, then new in chemistry, which were adduced in support of a theory I entertained as to the re-invigoration of the human system by principles similar to those which Liebig has applied to the replenishment of an exhausted soil,--namely, the giving back to the frame those essentials to its nutrition, which it has lost by the action or accident of time; or supplying that special pabulum or energy in which the individual organism is constitutionally deficient; and neutralizing or counterbalancing that in which it super-abounds,--a theory upon which some eminent physicians have more recently improved with signal success.
But on these essays, slight and suggestive, rather than dogmatic, I set no value.

I had been for the last two years engaged on a work of much wider range, endeared to me by a far bolder ambition,--a work upon which I fondly hoped to found an enduring reputation as a severe and original physiologist.

It was an Inquiry into Organic Life, similar in comprehensiveness of survey to that by which the illustrious Muller, of Berlin, has enriched the science of our age; however inferior, alas! to that august combination of thought and learning in the judgment which checks presumption, and the genius which adorns speculation.

But at that day I was carried away by the ardour of composition, and I admired my performance because I loved my labour.