Allen, Association in the Guinea Pig. 357 



The changes in the encephalon between birth and maturity 

 as exhibited in the figures may be recapitulated as follows : 



I. At birth no important cerebral pathways are unmedul- 

 lated. 



II. The number of fibers increases very greatly up to 

 maturity. 



III. The Amnion's horn corresponds in its development 

 to the cortex, and at birth has very few medullated fibers. 



IV. Few tangential fibers of the zonal layer are present 

 at birth, and at no time are such fibers numerous in the stratum 

 zonale of the guinea pig. 



Increase in Area of Cross Sections of the Encephalon. 



There are no observations showing the increase in weight 

 of the encephalon of guinea pigs between birth and maturity. 

 Linear measurements, however, show clearly that during this 

 period the encephalon increases in size as well as in number of 

 fibers. 



The^ area of the cross sections used for illustration, of 

 both cerebrum and cerebellum was measured, and is presented 

 in the following table : 



TABLE IV. 



Table showing the increase in area of cross sections of the encepha- 

 lon between birth and maturity. 



Table showing percentage increase in area of cross .sections of enceph- 

 alon between birth and maturity. 



[^5] 



