SIR WILLIAM CROOKES ON PSYCHICAL RESEARCH. 191 



race, therefore, has passed throug-h all its periods of evolution and 

 development in strict confoitnity with and submission to this dominant 

 power until it is difficult to conceive any great departure from the 

 narrow limits imposed on the proportions of the human fi-ame. 



In the lirst place. I wish to consider what transformation in our 

 appearance would be produced by a change in the force of gravitation. 

 Let us take extreme cases. Say that the power of gravitation were to 

 be doubled. In that case we should have to exert a vastly increased 

 strength to support ourselves in any other than the prone or dorsal 

 position, it would be hard to rise from the ground, to run. leap, climb, 

 to drag or carry any object. Our muscles would necessarily be more 

 powerful, and the skeleton to which they are attached would need cor- 

 responding modification. To work such limbs a more rapid trans- 

 formation of matter would be required: hence the supply of nutriment 

 must be greater, involving enlarged digestive organs, and a larger 

 respiratory appai'atus to allow of the perfect aeration of the increased 

 mass of the blood. To keep up the circulation with the necessary 

 force, either the heart would have to be more powerful or the distance 

 through which the blood would require to be impelled must be reduced. 

 The increased amount of nourishment demanded would involve a cor- 

 responding increase in the difficulty of its collection, and the struggle 

 for existence would be intensified. More food being required day by 

 day. the jaws would have to be enlarged and the muscles strengthened. 

 The teeth also must be adapted for extra tearing and grinding. 



These considerations involve marked changes in the structure of 

 human beings. To accord with thickened bones, bulging muscles, and 

 larger respiratory and digestive apparatus, the body would be heavier 

 and more massive. The necessity for such alterations in structure 

 would be increased by the liability to fall. The necessity of keeping 

 the center of gra\"ity low, and the great demands made on the system in 

 other respects, must conspire to reduce the size of head and brain. AVith 

 increase of graWtation the bipedal form would be beset by drawbacks. 

 Assimiing that the hmuan race, under the altered circumstances, 

 remained bipedal, it is highly probable that a large increase in the 

 quadruped, hexapod. or octopod structure would prevail in the animal 

 kingdom. The majority of animals would be of the saurian class, with 

 very short legs allowing the trunk to Test easily on the ground, and 

 the serpent type would probably be in the ascendant. AVinged crea- 

 tures would suffer severely, and small birds and insects would be 

 dragged to earth by a force hard to resist; although this might be 

 more or less compensated by the increased density of the air. Hum- 

 ming birds, dragon flies, buttei-flies, and bees, all of which spend a 

 large portion of their time in the air. would, in the struggle for exist- 

 ence, be rare visitants. Hence the fertilisation of flowers bv the inter- 



