522 FREDERICK S. HAMMETT. 



tive answer to this last point (17), and hence the reversal of 

 expected relationship is either a real objection to the theory or 

 else some other factor has intruded to mask the normal reaction. 

 Such a factor is present in the technic of removal of the spinal 

 cord for weighing. This is no place to describe the matter, nor 

 is it necessary, for a little consideration will show that when the 

 removal of an organ is accompanied by the cutting of many 

 connections, the technic (no matter how much care is exercised) 

 is bound to give a higher weight variability, than when the 

 removal is merely a matter of shelling an organ out of its envelope. 

 In view of this fact the brain-spinal cord difference in variability 

 gives no basis for an inter-organ biological interpretation. 



In a preceding paragraph mention was made of "reduced 

 variability." This is a statistical value purporting to show the 

 variability of a variable freed from influences assumed to be 

 exerted by the other variables being studied. I have calculated 

 these values for the body weight, body length, brain weight and 

 spinal cord weight, and have arranged them in the order of 

 decreasing variability in Table IV. as a matter of record. \Yhile 

 in every case the variability is less than that which obtains when 

 all factors of influence are in play, the relative position of any 

 variable in the general scheme is unchanged. 



TABLE IV. 



THE REDUCED VARIABILITY OF THE SEVERAL VARIABLES DISCUSSED IN THIS STUDY. 



Structure. Mali-. Female. 



Body Weight.. 11.41 9.86 



Spinal Cord 5.28 5.06 



Brain 4.35 4.08 



Body Length 3.65 2.93 



In the earlier study (i) on the weight inter-relationships of the 

 glands of internal secretion a similar computation was made of 

 the reduced variability of that particular array. It was found 

 that the thyroid has the highest variability of all the organs so 

 far studied, and that the thymus comes next. Both of these 

 organs are much more variable than the body as a whole. The 

 adrenals, gonads, hypophysis, and pancreas give lower figures, 

 but in all cases values considerably higher than those for brain 

 or spinal cord. 



