848 GENERATION. 



of the brain generally to be heavier on the left than on the right side. With 

 regard to the cause of the superior development of the left side of the brain, 

 the only explanation offered is the fact that the arteries going to the left side 

 usually are larger than those on the right. There are no observations with 

 regard to the comparative size of the arteries upon the two sides in left- 

 handed persons. 



Reasoning from the facts just stated, Ogle has assumed that dextral pre- 

 eminence depends upon a natural predominance of the left side of the brain, 

 the reverse obtaining in the left-handed. This view seems to afford the 

 most rational explanation of dextral pre-eminence. Generally it is true that 

 the members on the right side are stronger than the left, particularly the 

 arm ; but this is not always the case, even in the right-handed, although the 

 right hand is more conveniently and easily used than the left. In many 

 feats of strength, the left arm appears less powerful than the right, because 

 there is less command over the muscles. As regards the cause of the superior 

 development of the left side of the brain, it must be admitted that the ana- 

 tomical explanation is not entirely satisfactory. It is a fact, however, that 

 the two sides of the brain generally are not exactly equal in their develop- 

 ment, the left side usually being superior to the right, and that the muscles 

 of the right side of the body generally are used in preference to those of the 

 left side. 



DEVELOPMENT AFTER BIRTH, AGES AXD DEATH. 



When the child is born, the organs of special sense and the intelligence 

 are dull ; there is then very little muscular power ; and the new being, for 

 several weeks, does little more than eat and sleep. The natural food at this 

 time is the milk of the mother, and the digestive fluids do not for some time 

 possess the varied solvent properties that are found in the adult, though ob- 

 servations upon the secretions of the infant are few and rather unsatisfac- 

 tory. The full activity of pulmonary respiration is gradually and slowly 

 established. Young animals appropriate a comparatively small quantity of 

 oxygen, and just after birth they present a much greater power of resist- 

 ance to asphyxia than the adult. The power of maintaining the animal 

 temperature is also much less in the newly-born. The processes of ossification, 

 development of the teeth etc., have already been described. The hairs are 

 shed and replaced by a new growth a short time after birth. The fonta- 

 nelles gradually diminish in size after birth, and they are completely closed 

 at the age of about four years. 



The period of life which dates from birth to the age of two years is called 

 infancy. At the age of two years the transition takes place. from infancy 

 to childhood. The child is then able to walk without assistance, the food is 

 more varied and the digestive operations are more complex. The special 

 senses and the intelligence become more acute, and the being begins to learn 

 how to express ideas in language. The child gradually develops, and the 

 milk-teeth are replaced by the permanent teeth. At puberty, which begins 

 between the fourteenth and the seventeenth years a little earlier in the 



