of a given drug produces on no two persons exactly like sets of effects, and produces even on the same person different effects in different constitutional states, we see at once how involved is the combination of factors by which the changes in an organism are brought about, and how extremely contingent, therefore, is each particular change. And we need but watch what happens after an injury, say of the foot, to perceive how, if permanent, it alters the gait, alters the adjustment and bend of the body, alters the movements of the arms, alters the features into some contracted form accompanying pain or inconvenience. Indeed, through the readjustments, muscular, nervous, and visceral, which it entails, this local damage acts and reacts on function and structure throughout the whole body, producing effects which, as they diffuse, complicate incalculably.
While, in multitudinous ways, the Science of Life thrusts on the attention of the student the cardinal notions of continuity, and complexity, and contingency, of causation, it introduces him to a further conception of moment, which the inorganic Concrete Sciences do not furnish—the conception of what we may call fructifying causation. For, as it is a distinction between living and not-living bodies that the first propagate while the second do not, it is also a distinction between them that certain actions which go on in the first are cumulative, instead of being, as in the second, dissipative. Not only do organisms as wholes reproduce, and so from small beginnings are capable, by multiplication, of reaching great results; but components of them, normal and morbid, do the like. Thus a minute portion of a virus, introduced into an organism, does not work an effect proportionate to its amount, as would an inorganic agent on an inorganic mass; but, by appropriating materials from the blood of the organism, and thus immensely increasing, it works effects altogether out of proportion to its amount as originally introduced—effects which may continue with accumulating power throughout the remaining life of the organism. It is so with internally-evolved agencies as well as with externally-invading agencies. A portion of germinal matter, itself microscopic, may convey from a parent some constitutional peculiarity that is infinitesimal in relation even to its minute bulk; and from this there may arise, fifty years afterward, gout or insanity in the resulting man: after this great lapse of time, slowly-increasing actions and products show themselves in large derangements of function and structure. And this is a trait characteristic of organic phenomena. While, from the destructive changes going on throughout the tissues of living bodies, there is a continual production of effects which lose themselves by subdivision, as do the effects of inorganic forces, there arise from those constructive changes going on in them, by which living bodies are distinguished from not-living bodies, certain classes of effects which increase as they diffuse—go on augmenting in volume as well as in variety.
