462 LAWS OF MULTIPLICATION. 



There is yet another mode in which accumulation of fat 

 diminishes fertility. Even supposing it unaccompanied by 

 a smaller absorption of nitrogenous materials, it is still a 

 cause of lessening the surplus of nitrogenous materials. For 

 the repair of the motor tissues becomes more costly. Fat 

 stored-up is weight to be carried. A creature loaded with 

 inert matter must, other things equal, consume a greater 

 amount of tissue- forming substances for keeping its loco- 

 motive apparatus in order ; and thus expending more for self- 

 maintenance can expend less for race-maintenance. Abnormal 

 plethora is thus antagonistic to reproduction in a double way. 

 It ordinarily implies a smaller absorption of tissue-forming 

 matters, and an increased demand on the diminished supply. 

 Hence fertility decreases in a geometrical progression. 



The counter-conclusion drawn from facts of this class, is, 

 then, due to a misconception of their nature a misconception 

 arising partly from the circumstance that the increase of bulk 

 produced by fat is somewhat like the increase of bulk which 

 growth of tissues causes, and partly from the circumstance 

 that abundance of good food normally produces a certain 

 quantity of fat, which, within narrow limits, is a valuable 

 store of force-evolving material. "When, however, we limit 

 the phrase high nutrition to its proper meaning an abun- 

 dance of, and due proportion among, all the substances which 

 the organism needs we find that, other things equal, fertility 

 always increases as nutrition increases. And we see that these 

 apparently-exceptional cases, are cases that really show us the 

 same thing ; since they are cases of relative innutrition. 



h&ve their reproductive systems seriously affected. " Possibly the relative or 

 absolute arrest of genesis, is less due to a direct eifect on the reproductive sys- 

 tem, than to a changed nutrition of which the reproductive system most clearly 

 shows the results. The matters required for forming an embryo are in a 

 greater proportion nitrogenous than are the matters required for maintain- 

 ing an adult. Hence, an animal forced to live on insumeiently-nitrogenized 

 food, may have its surplus for reproduction cut off, but still have a sufficiency 

 to keep its own tissues in repair, and appear to be in good health meanwhile 

 increasing in bulk from excess of the non-nitrogenc is matters it cats. 



