552 NAOKI SUGITA 



B. Measurements corrected for the effects of technique 



The figures given in the foregoing table 5 and chart 1 were 

 based on the direct measurement of sections prepared by the 

 uniform technique as explained in a former chapter. But, since 

 the shape and volume of the brain suffer some passive changes 

 during preparation for study in this way, the values obtained by 

 measurement on the shde do not represent those for the cortex 

 in the fresh condition. We might think of these modified meas- 

 urements as comparable among themselves, but, as will appear 

 later, even that is not the case, since the change shown by a 

 brain is related to its age (or size) . 



Thus, during fixation in the Bouin's fluid, the younger brains 

 are little influenced in size, but, the more the age advances, the 

 more the fluid causes shrinkage during fixation in all dimensions, 

 especially in the sagittal direction. During fixation and dehy- 

 dration, while the brain is passing through the several grades of 

 alcohol, the older brain has more substance extracted by alcohol 

 than younger. As a matter of routine I took the total weight 

 of brain, just before it was transferred from 90 per cent into the 

 absolute alcohol. In younger brains the weight is reduced to 

 ca. 80 per cent of the fresh weight, while older brains, for ex- 

 ample, that of a rat 150 days old or more, are reduced in weight 

 to 66 per cent of the fresh weight.- Accordingly, of course, the 

 size of the total brain suffers more shrinkage, as the age ad- 

 vances, during the process of dehydration. 



It follows from this that the younger brain should have a rela- 

 tively thicker and the older brain a relatively thinner cortex on 

 the slide, as a result of the foregoing treatment. It is a question 

 whether the white and the gray substance respond in exactly the 

 same manner, but for the moment we assume that they do.. 

 Measurements indicate, however, that the shrinkage of fibers 

 along their length is larger than that along their transverse direc- 

 tion, but the difference is so small that it may be neglected. 



'^ Correction was not made for the weight lost by the replacement of water by 

 alcohol. Details on this point will appear in a later part of this series of studies. 



