468 C. G. MACARTHUR AND E. A. DOISY 



tractives, either organic or inorganic. Water decreases regularly 

 to maturity. 



2. In percentage of solids each of the lipins increases rapidly 

 until a few months after birth, then more slowly until maturity. 

 (Cerebrosides are not present in free condition till about the time 

 of birth.) The proteins slowly decrease in percentage of solids 

 with growth, but the extractives, both organic and inorganic, 

 very rapidly decrease. 



3. At birth most of the brain compounds are being laid down 

 most rapidly. Cerebrosides and sulphatids, however, have the 

 greatest daily additions about three months after birth. 



The following amounts, in milligrams, are added per day in a 

 new-born child: water 3270, solids 494, lipins 165, phosphatide 

 85, cholesterol + 70, sulphatids 7.7, cerebrosides 1.9, proteins 186, 

 organic extractives 100, inorganic extractives 44, sulphur 2.3, 

 phosphorus 8.5. 



4. The brain stem contains the largest percentage amounts of 

 total solids, total lipins, and of each lipin, but the least protein, 

 organic extractives, inorganic extractives, and water. The fore- 

 brain is not much different frQm the stem. The cerebellum, 

 however, varies largely. In development, the brain stem dif- 

 ferentiates chemically first and fastest. The forebrain follows 

 closely. The cerebellum never attains to such a high degree of 

 specialization. 



The data may indicate that the cerebellum is not only the 

 slowest and least meduUated, but that it remains the youngest 

 division of the brain with the highest rate of metabolism. 



5. It is suggested that, because of the early marked chemical 

 differentiation of the brain in the head end of the organism, 

 further development is greatly influenced by the central nervous 

 system. 



6. An attempt is made to correlate the data obtained with 

 the early differentiation of specialized nerve tissue and its con- 

 stancy in number of cells and composition. 



. 7. The chemical analyses agree that brain growth consists of 

 1) increase in the number of cells; 2) their growth, including that 

 of the axis cylinders, and 3) medullation. 



