CHANGES IN THE RELATIVE WEIGHTS OF THE VA- 

 RIOUS PARTS, SYSTEMS AND ORGANS OF YOUNG 

 ALBINO RATS HELD AT CONSTANT BODY-WEIGHT 

 BY UNDERFEEDING FOR VARIOUS PERIODS 



CM. JACKSON 



Institute of Anatomy, University of Minnesota, Minneapolis 



FOUR FIGURES 



CONTENTS 



Material and methods 100 



Length of body and tail 106 



Head 112 



Extremities and trunk 115 



Integument 117 



Skeleton 119 



Musculature 125 



Viscera and 'remainder' 127 



Brain 129 



Spinal cord 132 



Eyeballs 132 



Thyroid gland 134 



Th^^nus 135 



Heart 136 



Lungs 138 



Liver 139 



Spleen 140 



Stomach and intestines 141 



Suprarenal glands 143 



Kidneys 145 



Testes and epididymi 146 



Ovaries *. 147 



Hypophysis 148 



Discussion 149 



Summary 153 



Literature cited 155 



When young, actively growing animals are held at constant 

 body-weight by underfeeding for considerable periods, one of 

 three results might be expected a priori concerning the weights 

 of the various organs and parts. (1) Since the body-weight 



99 



THE JOURNAL OF EXPERIMENTAL ZOOLOGY, VOL. 19, >IO. 2. 

 AUGUST. 1915 



