METABOLISM IN CHANGED CEREBRAL ACTIVITY 35 



cells, axons and dendrites and occupies roughly the first ten days of 

 life in the rat, the first twenty days in the mouse and from the 

 40th-46th day of gestation in the guinea pig. In man this process 

 continues to birth. During this phase spontaneous electrical 

 activity can be detected from the cortex though the subcortex may 

 be silent (Flexner, 1955; Grain, 1952). Man differs in the activity 

 since at birth the waking infant shows no spontaneous electrical 

 activity recorded from the scalp (Hill, 1955). Topical application 

 of strychnine to guinea pig or rat cortex results in bursts of activity. 

 In the third stage growth largely ceases and the formation of myelin 

 sheaths around the axons is the predominant feature. Co-ordina- 

 tion of muscular movement begins. In the rat this occupies the 

 period between 10-20 days after birth, in the mouse from 10 to 30 

 days after birth, in man to 210 days after birth and in guinea pig 

 from the 46th day of gestation to birth. The fourth stage comprises 

 further myelination and the establishment of an adult pattern of 

 cortical and subcortical activity. 



During these stages there are marked increases in metabolic 

 processes such as oxygen consumption (Himwich, 1951). This is 

 accompanied by an increased dependence of the brain upon the 

 oxidation of glucose as a major source of energy for the main- 

 tenance of its function. Since the generation of energy in the form 

 of acid-hydrolysable phosphates is closely linked to such a process, 

 it might be expected that the quantities of phosphocreatine and 

 adenosine triphosphate would increase during the period of 

 development. 



This problem has been examined in several species. Data 

 obtained for the quantities of phosphocreatine in the brain of the 

 rat are shown in Fig. 6. The manner of presentation of results 

 obtained from analyses of developing brain have been discussed 

 in detail by Folch (1955) and Mcllwain (1959), and should be 

 referred to for details and sources of error. Here the data are 

 presented in three ways ; (a) related to wet weight, (b) as the total 

 quantity /brain, and (c) related to the content of desoxyribonucleic 

 acid. The period of maximal growth of the brain and develop- 

 ment of function (stage 3) is marked by a doubling or trebling of 

 the total quantity of phosphocreatine present, though the con- 

 centration/unit of mass increases only slightly. The concentration 

 relative to the content of desoxyribonucleic acid showed little 

 change. The amount of desoxyribonucleic acid is known to be 



