PRELIMINARY FEEDING PERIOD. The results recorded in Table I are especially valuable in view of the fact that they cover a period of practically one hundred days. During this time an attempt was made to mate the rabbits, each one being removed from her cage every four days at 5 o'clock and placed in a large box with a male rabbit and allowed to remain there until the next morning at 9 o'clock. This was repeated fifteen or twenty times in each case. Consequently some loss of feces and urine must have resulted, which loss in the course of an experiment extending over one hundred days would be practically uniform in the case of each pair of rabbits. Such a loss would naturally tend to give somewhat larger apparent nitrogen and phosphoric acid balThe rabbits had always eaten the food provided for them before being removed from their cages. ances. Throughout this work the rabbits fed organic phosphorus are given the numbers 1 and 2, and those fed inorganic phosphorus the numbers 3 and 4. The weight of the rabbits remained constant in the case of Nos. 1 and 4, while in the case of No. 2 a slight average loss of weight resulted and No. 3 showed a gain in weight. TABLE I.-Nitrogen and phosphorus metabolism—Preliminary period. No. 1.-RABBIT FED ORGANIC PHOSPHORUS. 1907-8. November 17-23. November 24-30.. December 1-7 December 8-14. Gms. Gms. Gms. Gms. Gms. Gms. Gms. Gms. Gms. P. ct. P. ct. P. ct. P. ct. 1,647 3.34 4. 22 0.95 0.28-0.08 92 .03 1.81 . 13, .901 .11 35 2.37 53 3. 13 January 19-25. January 26-Febru ary 1 1,623 7.44 5. 12 54 25 2.79 .81 .44 . 21 1,616 7.03 4.58 1.12 17 2.67 .63 1.95 .14 1,647 7.64 5.21 .74 24) 2.76 85 .91 .16 68.19 30.79, 1,597 9.56 6.40 1.08 1.587 10.06 6.06 1.32 February 2-8. 38 3.24 1.04 1.05 .16 1.588 10.19 7.34 1.02 .26 3.27 1.11 1.02 1,567 10.60 8.11 1.33 16, 3.23 1.80 1.16 1,585 10.10 6.98 Average for period. 1,618 8.08 5.65 a 1.42 grams of organic phosphorus per period were intimately mixed with the food. TABLE I.-Nitrogen and phosphorus metabolism--Preliminary period—Continued. No. 2. RABBIT FED ORGANIC PHOSPHORUS. 1907-8. November 17-23.. November 24-30. 1.728 4.32 6.09 .56- .33 1.98 .39 Gms. Gms. Gms. Gms. Gms. Gms. Gms. Gms. Gms. P. ct. P. ct. P. ct. P. ct. 1.35 0.82 0.45 0.01 1,816 4. 16 4.86 0.51 0.17 .76 .41 .16 .21 .17 a 1.42 grams of organic phosphorus per period were intimately mixed with the food. TABLE I.-Nitrogen and phosphorus metabolism-Preliminary period—Continued. No. 4.-RABBIT FED INORGANIC PHOSPHORUS. 1907-8. November 17-23. November 24-30. December 1-7.. December 8-14... 8.90 Gms. Gms. Gms. Gms. Gms. Gms. Gms. Gms. Gms. P. ct. P. ct. P. ct. P. ct. 1,950 8.89 0.76-0.10 3.10 1.541 0.49 0.15 a 1.72 grams of inorganic phosphorus per period were intimately mixed with the food. NITROGEN BALANCES. The rabbit which gained in weight, No. 3, received a larger amount of nitrogen than the others. In fact, the amount of nitrogen ingested in all cases varied somewhat, but the total during a period of seven days was from 5 to 6.6 grams of nitrogen per 1,000 grams of body weight, No. 3 receiving the largest relative amount. The average figures show that relatively more nitrogen was excreted in the urine in the cases of rabbits No. 1 and No. 2 (those fed organic phosphorus), than in the cases of No. 3 and No. 4 (fed inorganic phosphorus). The amount of nitrogen eliminated in the feces varied with the individual rabbit. No. 1 eliminated 10.6 per cent and No. 2, 14.6 per cent. No. 3 eliminated 13.8 per cent and No. 4 only 9.3 per cent in this manner. Nos. 1 and 2 retained a smaller proportion of the metabolized nitrogen than did Nos. 3 and 4, the figures being respectively 22, 24, 29, and 26 per cent. This means that the rabbits fed inorganic phosphorus retained a larger proportion of the absorbed nitrogen than did those fed organic phosphorus; and it appears that those fed organic phosphorus excreted in the urine a larger proportion of the ingested nitrogen, but did not utilize this nitrogen so well as did the rabbits fed inorganic phosphorus. PHOSPHORUS BALANCES. In all cases, excepting rabbit No. 3, the average amount of phosphoric acid ingested during seven days per 1,000 grams of body weight varied from 1.6 to 1.7 grams; in No. 3 the amount was 2.2 grams. More phosphorus was eliminated by rabbit No. 4 through the kidneys than in any other case. Both of the rabbits fed organic phosphorus and No. 3 fed inorganic phosphorus retained about the same amounts of the absorbed phosphorus (averaging 53 per cent), while the figure for No. 4 is much lower, only 42 per cent. From the average figures, it appears that the rabbits fed organic phosphorus eliminated a smaller percentage of the ingested phosphoric acid in the urine than those fed on inorganic phosphorus. It must be remembered that the amount of phosphoric acid eliminated by the kidneys does not necessarily represent the amount metabolized, for inorganic phosphorus ingested might and undoubtedly does pass through the kidneys without undergoing any change. Of the total phosphoric acid ingested, 32 per cent was found in the feces of No. 1 and 31 per cent in the feces of No. 4, while No. 2 and No. 3 eliminated in this manner 37 and 39 per cent, respectively. Although the rabbits fed inorganic phosphorus excreted a larger amount of phosphorus in the urine than did the others, they retained on the average less of the absorbed phosphorus. The ratio of nitrogen to phosphoric acid in the food is but slightly above 3:1. This shows a much larger proportion of phosphoric acid than is usually fed in a normal diet. The ratio of nitrogen to phosphoric acid in the urine varies from 5:1 to 7.5:1, being higher in the case of the rabbits fed organic phosphorus, owing to the relatively larger elimination of phosphoric acid in the urine of those fed inorganic phosphorus. This ratio in the feces is rather constant, averaging about 1.1:1 in all cases. The exact ratios are given in Table II. TABLE II.-Ratio of nitrogen to phosphoric acid in food and excreta-Preliminary period. The principal feeding experiment extended over a period of four weeks, and during this time complete nitrogen, phosphoric acid, calcium, and magnesium balances were determined, as well as the etheralcohol soluble phosphorus balance. In addition the inorganic phosphorus in the urine was determined by the uranium-acetate titration. method. Other salts, as well as the calcium and magnesium salts, are important for the welfare of the organism, but in phosphorusfeeding experiments the two named stand out most prominently. The second rabbit fed organic phosphorus was in poor condition during the test and died of pneumonia at the end of the second week; consequently the results in this case must not be given the same weight as in the others. Throughout this period all of the rabbits remained practically constant in weight. Nos. 3 and 4 received more nitrogen and phosphoric acid than did Nos. 1 and 2 on an average, but Nos. 1 and 4 received practically the same amounts. The nitrogen and phosphorus balances were positive, except in the case of rabbit No. 2, which died, and naturally would show a negative set of balances. NITROGEN BALANCES. The analytical data obtained during the experiment are recorded in Table III. TABLE III.-Nitrogen and phosphoric acid balances-Principal period. RABBITS FED ORGANIC PHOSPHORUS. a Including 1.38 grams of organic phosphorus added to the food per period. |