The ancient Spartans owed a good deal of their famous bravery, their bodily strength and beauty, as well as their mental energy and capacity, to the old custom of doing away with new-born children who were born weakly or crippled. We find the same custom to-day among many savage races. When I pointed out the advantages of this Spartan selection for the improvement of the race in 1868 (chapter vii. of the _History of Creation_) there was a storm of pious indignation in the religious journals, as always happens when pure reason ventures to oppose the current prejudices and traditional beliefs. But I ask: What good does it do to humanity to maintain artificially and rear the thousands of cripples, deaf-mutes, idiots, etc., who are born every year with an hereditary burden of incurable disease? Is it not better and more rational to cut off from the first this unavoidable misery which their poor lives will bring to themselves and their families? It is no use to reply that religion forbids it. Christianity also bids us give up our life for our brethren, and to cast it from us when it hurts us--that is to say, when it only causes useless pain to us and our friends. The truth is, the opposition is only due to sentiment and the power of conventional morality--that is to say, to the hereditary bias which is clothed in early youth with the mantle of religion, however irrational and superstitious be its foundation. Pious morality of this sort is often really the deepest immorality. "Laws and rights creep on like an eternal sickness;" this is equally true of the social customs and morals on which laws and rights are founded. Sentiment should never be allowed to usurp the place of reason in these weighty ethical questions. As I pointed out in the first chapter of the _Riddle_, sentiment is a very amiable, but a very dangerous, function of the brain. It has no more to do with the attainment of the truth than what is called revelation. That is well seen in Kant's dualism, for his _mundus intelligibilis_ is essentially an outcome of his religious sentimentality VI PLASM Plasm is the universal living substance--Definition of protoplasm, chemically and morphologically--Physical character--Viscous condition--Chemical analysis--Colloid character of albumin--Albuminoid molecules--Elementary structure of plasm--Work of plasm--Protoplasm and metaplasm--Structures of metaplasm--Frothy structure--Skeletal structure--Fibrous structure--Granular structure--Molecular structure--Plasma molecules--Plastidules and biogens--Micella and biophora--Caryoplasm and cytoplasm--Nuclear matter--Chromatin and achromin--Nucleolus and centrosoma--Caryotheka and caryolymph--Cellular matter--Plasma products--Internal plasma products--External plasma products--Cell membranes--Intercellular matter--Cuticular matter.