heart with valves, by the aid of which the blood is propelled through the lungs for aëration, and throughout the system at large for general purposes. If this four-chambered heart is a perfect organ, what is the primitive heart, and what are the hearts possessed by all the multitudinous creatures below the higher _vertebrata_? Manifestly the process of evolution implies a continual replacing of creatures having inferior organs, by creatures having superior organs; leaving such of the inferior as can survive to occupy inferior spheres of life. This is not only so throughout the whole animal creation up to Man himself, but it is so within the limits of the human race. Both the brains and the lower limbs of various inferior races are ineffective organs, compared with those of superior races. Nay, even in the highest type of Man we have obvious imperfections. The structure of the groin is imperfect: the frequent ruptures which result from it would have been prevented by closure of the inguinal rings during fœtal life after they had performed their office. That all-important organ the vertebral column, too, is as yet but incompletely adapted to the upright posture. Only while the vigour is considerable can there be maintained, without appreciable effort, those muscular contractions which produce the sigmoid flexure, and bring the lumbar portion into such a position that the “line of direction” falls within it. In young children, in boys and girls who are admonished to “sit up,” in weakly people, and in the old, the spine lapses into that convex form characteristic of lower _Primates_. It is the same with the balancing of the head. Only by a muscular strain to which habit makes us insensible, as it does to the exposure of the face to cold, is the head maintained in position. Immediately certain cervical muscles are relaxed the head falls forward; and where there is great debility the chin rests permanently on the chest. So far, indeed, is the assumption of Kant from being true that the very reverse is probably true. After {206} contemplating the countless examples of imperfections exhibited in low types of creatures, and decreasing with the ascent to high types, but still exemplified in the highest, anyone who concludes, as he may reasonably do, that Evolution has not yet reached its limit, must infer that most likely no such thing as a perfect organ exists. Thus the basis of the argument by which Kant attempts to justify his assumption that there exists a good will apart from a good end, disappears utterly; and leaves his dogma in all its naked unthinkableness.[25]