This is the period of the "morning sickness," established in pregnant women during the fourth to sixth week, and accompanied by lack of appetite, vomiting, emaciation, and usually sallowness of face. Dissimilation of tissue and gastrointestinal disturbances are accompanying phenomena.

One of Murlin's2 experiments covering the period of gestation in a dog is given below:

Weekly Nitrogen Balance In A Pregnant Dog

* Four days only.

† 69.7 calories per kilogram.

‡ 61.0 calories per kilogram.

1 Hagemann: "Inaugural Dissertation" Erlangen, 1891; Jagerroos: "Archiv fur Gynakologie," 1902. lxvii, 517.

2 Murlin: "American Journal of Physiology," 1910, xxvii, 177.

This shows the large loss of maternal protein commencing immediately after conception and continuing for six weeks. Only during the last two weeks is there a marked conservation of protein as manifested in the pronounced nitrogen retention.

Some very instructive experiments have been performed to ascertain the course of the protein metabolism before and after pregnancy in women.

Zacharjewski1 investigated the nitrogen metabolism of 9 pregnant women. In 3 primiparae, nourished on diets containing an average of 16.5 grams of nitrogen, there was an average daily retention of 1.4 grams in the mother's organism for thirteen days before parturition. In 6 multiparas the diet contained 20.6 grams of nitrogen, and there was a daily retention of 5.12 grams of nitrogen during the last eighteen days of pregnancy. The figures correspond to a considerable construction of protein tissue within the organism. After childbirth there was always a loss of tissue nitrogen by the mother. In 1 case nitrogen equilibrium was established on the fifth day, and in another on the fourth. In 6 cases the loss of body nitrogen continued over a longer time. Zacharjewski says that the process of involution of the uterus is greatest during the first five to seven days after delivery, and the high nitrogen output from the mother is the result of this. After the elimination which is due to these regressive changes there is a retention of nitrogen. This is probably attributable to the building up of the mammary glands, for Slemons2 shows that nitrogen equilibrium, once established, was constantly maintained in a woman who did not nurse her child.

The complete record of the nitrogen elimination of a nursing mother, one of Slemons' cases, is here reproduced. It is especially instructive on account of the constancy of the quantity of nitrogen in the diet. The woman was a negress who gave birth to a healthy, vigorous child.

1 Zacharjewski: "Zeitschrift fur Biologie," 1894, xxx, 405.

2 Slemons: "Johns Hopkins Hospital Reports," 1904, xii, 121.

Protein Metabolism Before And After Childbirth

(Weights are in Grams)

During the last days of pregnancy there was an average daily storage of 2.98 grams of nitrogen, and for eight days of the puerperium an average loss of 4.5 grams. Later, between the nineteenth and twenty-fifth days after parturition, there was an average daily storage of 2.52 grams of nitrogen. This may have been for the purpose of increasing the size of the breasts. It must be remembered that even during the period of involution an increase in the mammary glands may have been taking place at the expense of protein derived from the uterus. So the debit balance of nitrogen during this period may not represent all the protein change taking place.

An elaborate experiment upon the subject of the metabolism of the pregnant woman was carried out by Hoffstrom,1 and extended over the period of the last twenty-three weeks of pregnancy. He computes the probable composition of the ovum at the end of the sixteenth week and compares that with the estimated composition of the child at birth, and also computes the constituents of the food retained for the growth of the child and the mother:

There was an irregular retention of magnesium. Rapid growth of the fetus began during the twenty-ninth week of pregnancy, at which time the calcium retention by the organism greatly increased and the excretion of calcium in the feces of the mother diminished. The retention of materials by the mother herself represents the requirement for the growth of the uterus, the breasts, the gluteal and leg muscles.

Hoffstrom gives the following computation of the growth of the fetus:

Growth Of The Human Fetus Computed From The Tables Of Michel

1 Hoffstrsm: "Skan. Archiv fur Physiologie," 1910, xxiii, 326.

It is obvious that during the last ten weeks of pregnancy a diet which is rich in calcium is indicated, or there may be a withdrawal of calcium from the mother's bones. Cows' milk contains much calcium and is a highly desirable addition to the dietary of the pregnant woman. (See p. 374).

Rubner and Langstein1 have investigated the metabolism of two prematurely born infants. One of them was born at the end of the seventh month of pregnancy and weighed 2050 grams. On the eighth day the child weighed 1900 grams, and then gained an average of 28 grams daily until the twenty-seventh day, when it weighed 2360 grams. At this point respiration experiments were introduced. During the next eleven days the child gained 39 grams daily. During this same period the child received each day 1.04 grams of nitrogen in milk and retained 0.52 gram, or 50 per cent, of the intake. At this period, which would have corresponded to the beginning of the eighth month of pregnancy, the addition of protein to the child amounted to only one-half that computed by Hoffstrom for the fetus of the same age. The fat retained per day averaged 14.6 grams. The diet contained 126 calories per kilogram of body weight, of which 73 were used for heat production (973 calories per square meter per day) and 53 were deposited in the growing infant. In all, 42 per cent, of the calories ingested in the food were retained for growth, a remarkably large amount. The so-called "growth impulse" must have been very great. The second prematurely born infant showed the same capacity for protein retention as the first, but the amount of fat retained was much less.