If medical progress simply involved the investigation of inorganic Nature, the general public would be only learners, gladly receiving such information in geology, chemistry, astronomy, or physics, as specialists in those branches of physical science were good enough to impart to the unlearned. But directly scientific research passes beyond the distinctive realm of matter, moulded and transformed by general energy, but not affected by individual will, it has to deal with a very different principle--viz., life. This vital distinction has been well laid down by one of our eminent medical authorities as follows: ‘During the slow growth of medical knowledge it has become more and more plain that physics, chemistry, and biology are distinct sciences, with methods of their own and inductions of their own, each of the latter terms in the series using the results of its predecessors, and adding new results of its own. Although life is a structure built up of physical and chemical facts, yet to the building, to the arrangement, to the ordering of those facts, there goes something that neither physics nor chemistry can explain, any more than algebra can explain the behaviour of a magnet. To strive to interpret the series of events which make up the life of an animal in terms of chemical change (metabolism), or of conservation or expenditure of energy, is an endeavour which will fail.’ As the brute creation as well as human beings share in a physical organization which expresses each variety of life, there is not the same sharply-dividing line between the various categories of animal life as there is between organic and inorganic Nature. Biogenesis, or life generated by life, is the distinctive feature of organic Nature. We are linked to living creatures of higher or lower nature by the power of educating or subduing them, and by all those varying relations involved in the mystery of life. The distinctive position of man, as an animal placed at the head of the animal world, necessarily creates serious responsibility on the part of the higher towards the lower creature. This basis of moral responsibility extends in kind, if not in degree, to all life. It necessitates a directing conscience which shall guide all our intellectual and practical relations with every category of life. This moral element enters unavoidably into our treatment of animal life from its lowest to its highest form. Our treatment of a monkey or a prince contains an element of moral attitude which does not exist in our relation to inorganic Nature. It is a difference of kind as well as of degree, which it is blindness to ignore. The divergence which now exists between some biological investigators and their critics rests upon the failure to recognise that moral error may engender intellectual error.