CORRELATION OF BRAIN AND SPINAL CORD. 517 



body length which are caused by thyroid and parathyroid removal 

 at different ages, to a lesser degree than does that of the male. 



A general analysis of the progress of partial correlation would 

 naturally only be an extension and confirmation of the com- 

 parisons made from the zero order values. As an example: the 

 association between brain weight and spinal cord weight is con- 

 ditioned to a lesser degree by body length than by body weight. 

 This is shown by the fact that the percentage reduction in degree 

 of association between brain and spinal cord weight from the zero 

 order value (r 3 4), is greater when body \veight is held constant 

 (r 34 1) than when body length is held constant (r 342 ). The 

 difference is w r hat is to be expected from the fact noted earlier 

 that brain weight and spinal cord weight are more closely associ- 

 ated with body weight than with body length. 



It is important to note that there is a high degree of positive 

 correlation between brain weight and spinal cord weight (r 34 12) 

 which is independent of the general factors for size carried by the 

 body as a whole. Indeed this value is much higher than that 

 found for any of the pairs of organs so far studied (thyroid, 

 adrenals, hypophysis, gonads, thymus and pancreas (i)). Be- 

 tween many of these no correlation was present at all after 

 stabilization for body weight. Such being the case it is evident 

 that the uncomplicated weight association between brain and 

 spinal cord is peculiar. The phenomenon can be attributed to 

 the community of characteristic chemical (lipoid) make-up of the 

 two organs as already noted. As far as simple correlation with 

 body weight is concerned, the brain and spinal cord have also a 

 higher degree of association than any of the above, save the 

 hypophysis and the pancreas in the male. The value of r is 

 0.701 0.031 for the hypophysis, and 0.600 0.039 f r the 

 pancreas. It might be noted that since the same animals served 

 as original sources of the material used in both studies, the 

 value of the comparisons is enhanced. 



There is no sex difference in the degree of association between 

 brain w r eight and spinal cord weight freed from the general factors 

 for size (73412). The significance of this relation has been dis- 

 cussed in an earlier paragraph. 



Another statistical value of assistance in an estimation of the 



