"As affording the simplest and most conclusive proof that the degree of life varies as the degree of correspondence, it remains to point out that perfect correspondence would be perfect life. Were there no changes in our environment but such as the organism had adapted changes to meet, and were it never to fail in the efficiency with which it met them, there would be eternal existence and universal knowledge. Death by natural decay occurs because in old age the relations between assimilation, oxidation, and the genesis of force going on in the body gradually fall out of correspondence with the relations between oxygen and the food and absorption of heat by the environment. Death from disease arises either when the organism is congenitally defective in its power to balance ordinary internal actions, or when there has taken place some unusual external action to which there was no answering internal action. Death by accident implies some neighboring mechanical changes of which the causes are either unobserved from inattention, or are so intricate their results cannot be foreseen, and, consequently, certain relations in the organism are not adjusted to the relations in the environment. Manifestly, if, to every outer co-existence and sequence by which it was ever in any degree affected, the organism presented an answering process or act, the simultaneous changes would be indefinitely numerous and complex, and the successive ones endless, the correspondence would be the greatest conceivable and the life the highest conceivable, both in degree and length." KNOWLEDGE.--Another requirement to promote human health is a better knowledge of how the constitution of the body may be strengthened, and more certitude as to whether such improvements as it may receive by hygienic training will be transmitted to offspring. That human health may be improved by right training of the body, a better supply of fresh air, greater moderation in living, there is not a shadow of doubt; but is the constitution itself thus strengthened, or only its original vigor conserved and made effective? I have been working on the problem for some time by a series of studies on the blood, and especially the amount of living matter in the colorless corpuscles, and have satisfied myself, from some observations on individual cases, that the original constitution of feeble persons can be strengthened in early life, but the extent of this strengthening seems somewhat limited. Much original research is still required to get at important facts in this direction. If some of the study now given to micro-organisms could be devoted to this subject it would be most useful. The work might be done in connection with our numerous schools of physical culture, now happily multiplying, and also in our physiological laboratories.