Motor ability in most of its forms is better in men than in women. In strength, rapidity of movement, and rate of fatigue they have a very decided advantage. These three forms of superiority are probably all expressions of one and the same fact--the greater muscular strength of men. Men are very slightly superior to women in precision of movement. This fact is probably also connected with their superior muscular force. In the formation of a new co-ordination women are superior. The superiority of men in muscular strength is so well known that it is a universally accepted fact. There has been more or less dispute as to which sex displayed greater manual dexterity. According to the present results, that depends on what is meant by manual dexterity. If it means the ability to make very delicate and minutely controlled movements, then it is slightly better in men. If it means ability to co-ordinate movements rapidly to unforeseen stimuli it is clearly better in women.[44] We have no other than a utilitarian basis for judging some variations advantageous and others disadvantageous. We can estimate them only with reference to activity and the service or disservice to the individual and society implied in them, and a given variation must receive very different valuations at different historical periods in the development of the race. Departures from the normal are simply nature's way of "trying conclusions." The variations which have proved of life-saving advantage have in the course of time become typical, while the individuals in which unfavorable variations, or defects, have occurred have not survived in the struggle for existence. Morphologically men are the more unstable element of society, and this instability expresses itself in the two extremes of genius and idiocy. Genius in general is correlated with an excessive development in brain-growth, stopping dangerously near the line of hypertrophy and insanity; while microcephaly is a variation in the opposite direction, in which idiocy results from arrested development of the brain, usually through premature closing of the sutures; and both these variations occur more frequently in men than in women. There is also evidence that defects in general are more frequent in men than in women. A committee reported to the British Association for the Advancement of Science, in 1894,[45] that of some 50,000 children (26,287 boys, and 23,713 girls) seen personally by Dr. Francis Warner (1892-94) 8,941 were found defective in some respect. Of these, 19 per cent. (5,112) were boys, and 16 per cent. (3,829) were girls. An examination of 1,345 idiots and imbeciles in Scotland by Mitchell showed the following distribution of the sexes: Male Female Male Female Idiots 430 284 or 100 to 66.0 Imbeciles 321 310 or 100 to 96.5