264 GROWTH OF PARTS AND ORGANS 



Relative percentage weights of viscera and organs (Donaldson, ' 

 All viscera (12). 9 See list, table 153. 



From table 153 we may compute the percentage weights of all 

 the (12) viscera for a series of selected body weights. The data 

 are entered in table 154. 



When the percentage weight at birth is taken as unity, the 

 relative percentage values at the selected body weights may be 

 determined. These for all the viscera are entered in table 155 

 and the corresponding graphs are given in chart 49-1. 10 



The graphs show a maximum relative value at 25 grams, while 

 at 400 grams this value is about that found at birth. Whether 

 the sex difference here shown is significant is a question. 



Individual viscera and other organs (20}. Proceeding in the 

 same manner as in the case of all the viscera, the relative per- 

 centage weights have been determined separately for each of the 

 twenty organs at each of the selected body weights, and these 

 are entered in table 156. 



When the relative percentage weight shows a maximum before 

 25 grams of body weight, this is also entered. The organs have 

 been listed in table 156 first, in the order of the increasing final 

 relative weight (males) for those organs which do not show a 

 post-natal maximum, and second, in the order of the body 



9 The term "viscera" as generally used, is one of convenience, and it is de- 

 sirable to note that the list of organs here used as viscera differs from that of 

 Jackson and Lowrey ('12) by containing the submaxillaries and hypophysis 

 and by lacking the brain, spinal cord, eyeballs, thymus and gonads. 



The alimentary tract of Jackson and Lowrey includes the stomach, pancreas 

 and intestinal tract. This list differs from theirs in naming these parts sep- 

 arately. This list of organs differs also from that used in table 73 (The Rat. 

 '15) in containing the submaxillaries and in lacking the gonads and the thymus, 

 while the alimentary tract, as given in table 73, is equivalent to the pancreas 

 and intestinal tract combined. The data for the weight of the intestinal tract 

 are still in manuscript form. 



10 In this and the subsequent charts of this series the scale on the base line 

 changes at 50 grams; the entry for which is put in twice. Before 50 grams one 

 division has the value of 5 grams after 50 grams, the value of 20 grams. 



