678 EXPERIMENT STATION RECORD. [Vol.41 



Contributions to the physiology of phosphorus and calcium metabolism as 

 related to milk secretion, E. B. Meigs, N. R. Blatherwick, and C. A. Caey 

 (Jour. Biol. Chem., 37 {1919), No. 1, pp. 1-15, figs. If). — This puijer, a contribu- 

 tion from the Dairy Division of the U. S. Department of Agriculture, presents 

 and discusses the protocols of experiments with 15 dairy cows and heifers in 

 which the phosphorus, and in some cases the calcium, content of the blood was 

 observed either at intervals during the normal processes of growth, pregnancy, 

 and lactation, or for shorter periods under test conditions. 



Three cows in milk and 2 dry were used in a study of the blood plasma pre- 

 cursors of milk phosphorus and milk fat. The experimental procedure con- 

 sisted of obtaining approximately simultaneous samples of blood from (1) the 

 jugular vein, and (2) the subcutaneous abdominal (anterior "milk") vein of 

 each animal and analyzing the blood and plasma from such samples for total 

 phosphorus, phosphatids, and inorganic phosphorus. Sample 1 was taken to 

 represent blood which had not pas.sed through the mammary gland and sample 2 

 blood which had. Where the mammary gland was active and the experiment 

 proceeded without undue disturbance to the animal, less phosphatid was found 

 in the abdominal than in the jugular plasmas. No essential differences were 

 observed between lactating and nonlactating individuals with respect to inor- 

 ganic phosphorus of the plasma ; In both, the milk vein contained more than the 

 jugular vein. No evidence was found of the occurrence in the plasma of any 

 class of phosphorus compounds other than phosphatids and inorganic phos- 

 phorus. The deductions drawn are as follows: 



" The fat and phosphorus which are excreted with milk come from some phos- 

 phatid body or bodies in the blood. This material is converted in the mammary 

 gland cells to inorganic phosphate and neutral fat ; it yields 2.5 or more parts 

 of phosphorus to 45 of fat ; and, as milk contains only about one part of phos- 

 phorus to 45 of fat, some 60 per cent of the phosphorus which enters the gland 

 cells with the phosphatid precursor of milk fat must be returned to the blood as 

 inorganic phosphate. . . . The taking up of phosphatid by a cow's gland is 

 stopped if she is subjected to an even slight psychological disturbance." The 

 rate at which the taking up of phosphatid occurs is held to be sufficient to 

 account for the daily production of milk fat. The back flow of inorganic phos- 

 phorus, it is claimed, would be difficult to explain if the milk fat is derived even 

 in part from fats in the blood. 



Data on the relation of age to the blood phosphorus were obtained from 5 ani- 

 mals. For the tirst few days after birth the corpuscle phosphorus was about 

 twice as high as in older animals, but the condition rapidly disappeared and was 

 hardly noticeable at four months. The plasma phosphatid of newborn calves 

 was very low and increased gradually during the first year. The inorganic 

 phosphorus in the plasma was fairly high at birth but did not reach a maximum 

 until six months; it then fell off again. 



The effect of decrease in the weight of feed given on the blood phosphorous 

 was studied with 2 cows at the height of lactation. The total phosphorus in 

 both blood and plasma, the phosphatid and inorganic phosphorus in the plasma, 

 the total phosphorus in the corpuscles, and the relative volume of the cor- 

 puscles fell off during the period of low feeding and recovered when heavier 

 feeding was resumed. The inorganic compounds were more responsive to ration 

 changes than the phosphatids. During low feeding there was a more or less 

 clearly marked inverse relation between the concentration of phosphatid in the 

 plasma and the daily milk yield. " We are inclined to explain this by supposing 

 that the phosphatid was poured into the plasma at a nearly constant rnte during 

 this period, and that its concentration in the plasma therefore varied inversely 

 witk the rate at which it was excreted in the milk." 



