46 ?HE GROWTH OF tHE BRAlN*. 



groxvth, any more than does the increase in stature 

 which occurs each day during the hours of sleep. 

 Moreover, to the term growth, implying increase in size, 

 there is usually attached the notion of an increase in 

 power and capacity for work which are qualitative 

 changes. The word growth, therefore, has certain dis- 

 advantages, by virtue of its several connotations, so that 

 it will be better to employ, so far as possible, other terms 

 intended to be more exact 



Between the first changes in the fertilised ovum, and 

 the somatic death of the individual, is comprised a life 

 cycle. Within this cycle we recognise the following 

 subdivisions : the embryonic period, when the organs 

 are being formed ; the fcetal period, between the 

 formation of organs and the time of birth ; infancy, the 

 period of dependence upon the mother in medical 

 jurisprudence extending to the time when the milk 

 teeth begin to be shed childhood, from the beginning 

 of independence to the age of puberty ; youth, from 

 puberty to the completion of the increase in both stature 

 and weight ; maturity, from the completion of growth 

 to the onset of uncompensated decay ; old age, from 

 the beginning of uncompensated decay to death. Much 

 stress must not be placed upon any such division, since 

 it is only an attempt to break up a really continuous 

 process, an attempt which can never be satisfactory, but 

 which has its apology in convenience, and in the fact that 

 it defines some useful terms. Within the life cycle and 

 its periods cells undergo first increase, then decrease 

 in size, weight, and number. These may be designated 

 as growth changes. At the same time adaptive altera- 

 tions take place in cell structure and constitution, and 

 these are the changes of development. The term 

 development, then, will be used when changes in the 

 arrangements or chemical constitution of the cell sub- 



