Note 62 — Chapter IX · COINCIDENCE BETWEEN HIGH NUTRITION AND GENESIS.

It is worth while inquiring whether unfitness of the food given to them, is not the chief cause of that sterility which, as Mr. Darwin says, “is the great bar to the domestication of animals.” He remarks that “when animals and plants are removed from their natural conditions, they are extremely liable to have their reproductive systems seriously affected.” Possibly the relative or absolute arrest of genesis, is less due to a direct effect on the reproductive system, 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 maintaining an adult. Hence, an animal forced to live on insufficiently-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-nitrogenous matters it eats.