42 THE GROWTH OF THE BRAIN". 



growth processes go on diminishes from the first With 

 their cessation begins the period of decay. 



Starting with these ideas as introductory to the study 

 of growth, a few words maybe devoted to an outline of 

 the manner in which it is proposed to apply and expand 

 them. The arrangement is determined by the wish to 

 focus on the question of brain growth as many groups of 

 facts as will lead to the better comprehension of it. The 

 growth of the entire body is therefore first to be studied, 

 and then, since the different tissue systems are mutually 

 interdependent, such facts as bear on them separately 

 will be introduced. In the skeleton it is the growth of 

 the skull which is important for our purpose, since it 

 exercises a direct influence upon the enclosed brain. 

 We naturally pass from this to the growth of the brain 

 itself, and the conditions which more directly modify it. 

 Of course with it the spinal cord must be considered, as 

 together they form a unit, the Central Nervous System. 

 The normal brain first claims attention, and we shall 

 begin by discussing from the statistical point of view its 

 average weight and size ; but since the brain is the 

 main object in this study, it seems justifiable also to 

 introduce some of the facts .concerning its abnormal 

 development. This will enable us to estimate in a 

 measure the value of those speculations which involve 

 the assumption that the delinquent and dependent 

 classes in modern society are largely the victims of 

 their own nervous organisation. The facts, however, up 

 to this point have been gathered entirely from observa- 

 tions made on the organ taken as a whole, and their 

 interpretation . will become much more evident after 

 considering the meaning of the size, number, and 

 general arrangement of the elements of which the 

 central nervous system is composed, for the nerve cell 

 stands in the same relation to the system of which it is 



