TRANSMISSION OF MODIFICATIONS 371 



amount consumed is many times greater than that actually used 

 in body building. 



In acclimating to a shortened food supply the animal or plant 

 is forced, not so much to make more economical use of what it 

 can obtain as to reduce the scale of living and actually to accom- 

 plish less in the way of growth and functional activity generally. 

 A starving animal or plant will make the most of all available 

 food, but in addition the animal will replace a large share of the 

 dry matter of the body with water and reduce its activity to a 

 minimum before it succumbs, and a starving plant will still put 

 forth new leaves, using the substance of the old to nourish 

 the new. 



If the shortage in food comes before development is complete 

 its effect is seen in under-development, or possibly in arrested 

 development, recognized by the farmer under the term 

 " stunted." Sometimes the condition is only temporary, but 

 more often it is permanent, when no amount of food later in life 

 will avail to repair the damage done by shortage during devel- 

 opment. Farmers accordingly recognize the period of growth 

 as a " critical period," and uniformly say that if any live stock 

 is to be short of feed let it be the older ones. Sad experience 

 has taught the irreparable evil of shortage in food during 

 development. 



Under-nourishment strikes at the very root of life as well as 

 at development. What is true of individuals seems true of 

 races. Under-nourishment is followed by a lowering of tone 

 and a lessened rate of living, while full feed and maximum con- 

 ditions of life generally induce great protoplasmic activity and 

 rapid cell division, resulting in maximum size and maximum 

 functional activity in all parts of the structure. 



All experience goes to show that weakened parents, plant or 

 animal, give rise to young that are low in vigor and slow of 

 growth. Seed corn that is below the normal in vitality, though 

 it may germinate, will give rise to weak and slow-growing plants. 



There are all degrees of vigor and intensity of the vital 

 processes, from zero up, and nothing seems more potent than 

 the food supply in influencing this matter that lies at the basis 

 of all development and all functional activity. 



