The question will naturally arise in the mind of the reader as to whether the failure of the young to grow when nursed by these mothers, which were confined to faulty diets, was not the result of diminished milk production rather than of deviation of the secretion from the normal composition. It has not been found possible to secure complete information as to the actual amount of milk which any of these mothers secreted. The records of studies on women and on domestic animals, described in the early part of this chapter, afford abundant evidence that it is the quality which first falls off. Only when the lactating mother is brought to the verge of breakdown, does the flow of milk drop to a low level. The occurrence of infantile beri-beri rather than death from starvation, further serves to prove that it is milk of poor quality rather than of insufficient quantity which is responsible for the high infant mortality in those parts of the world where the poorer classes live too largely on food-stuffs derived from muscle meats and from plant products, the biological functions of which are those of storage organs. (See Chart X.)

Table XI. Showing The Rate Of Growth Of Young Rats When The Diet Of The Mother Is Of Fairly Satisfactory To Good Quality

*The diets of lots 2069 and 2153 were less satisfactory than the others. On these two diets the animals in the second and succeeding generations became progressively stunted.

Table XII Composition Of Diets Used In Experiments Described In Table XI

* Merrill-Soule Whole milk powder.

† Bolted wheat flour.

‡ Degerminated cornmeal.

§ Desiccated cabbage, subsequently steamed and dried.

Table XIII Showing The Stunting Effect On The Nursing Young Of Deficiency Of Calcium In The Diet Of The Mother

* Diet consisted of wheat, maize, rice, oats, peas, beans, casein, NaCl, butter fat and cod liver oil. (See p. 349.) † 2733 Diet same as 2785 except that cod liver oil was the only fat added, and casein was substituted by beefsteak. ‡ Diet consisted of beefsteak, oats, peas, beans, rice, cabbage, wheat flour, corn meal, CaCO3, and NaCl. § Diet similar to 2733 but with Jess cod liver oil. (See p. 349.)

|| Diet closely similar to 2785, but contained 0.5 per cent of added CaCO3. Note benefit to growth of young. ¶ Diet like 2785 except that casein was omitted. (See p. 349.)

**Diet similar in properties to the others used in these experiments but with the optimal amount of calcium carbonate added (1.5 per cent). Note the remarkable stimulating effect on the growth of the young.

Table XIV. Composition Of Diets Used In Experiments Described In Table XIII

*Cabbage desiccated, steamed and subsequently dried.

† Bolted wheat flour.

‡ Degerminated corn meal.

§ Norwegian cod liver oil employed in all experiments.

Table XV. Showing Weight Changes Of Female Rats And Their Young During The Nursing Periods As Influenced By The Character Of Their Diet

* Diet very good. It consisted of wheat, maize, oats, rice, peas, beans, beefsteak, NaCl, CaC03, and butter fat. Full formula is given on page 351. There was no deterioration observable in the 4th generation.

† The females of the 2nd generation never had any young. The diet consisted of milled wheat flour and maize meal, polished rice, oats, peas, navy beans, beefsteak, NaCl, and CaC03. The first generation did very well for about eight months, then failed rapidly. The 2nd generation failed very early without reproducing. Formula on page 351.

‡ Similar to 2153, but contained 10 per cent of cabbage. Family at first did well, but deteriorated rapidly with each succeeding generation. The 4th generation were in poor condition and had no young.

§ Similar to 2436, but contained no butter fat, and was alkalinized with HNaC03. Fertility good and infant mortality low, but each succeeding generation was decidedly smaller than its parents. The fourth generation was discarded in a stunted condition at the age of 2½ months. These experiments show the value of continuing observations over several generations, for they illustrate the tendency toward degeneration when the diet is faulty in even a slight degree.

Table XVI. Composition Of Diets Used In Experiments Described In Table XV

*Bolted wheat flour.

† Degerminated corn meal.

‡ Polished rice.

§ Desiccated cabbage, subsequently steamed and dried.