50 A Shiflfi of Xifroficn Metaho/iniii in tli< Dah-ij Coir 



result of changos in the early stages of pregnancy, was suffering a loss of 

 protein. 



This behaviour is in accord with the findings in other investigations 

 carried out on different species. Murlin^ investigated the weekly nitrogen- 

 balances in a ]jregnant bitch and showed that there was a large loss 

 of maternal protein, commencing immediately after conception and 

 continuing for six weeks. Only during the last two weeks before parturi- 

 tion was there a marked conservation of protein, as manifested in the 

 pronounced nitrogen-retention. Murlin attributed the destruction of 

 maternal protoplasm which accompanies the development of the foetus 

 to the necessity for providing "hereditary building stones for the laying 

 down of the youthful protoplasm in accordance with the type character- 

 istic of the species." 



The diet of Cow D was increased by 1 lb. seeds hay per day on day 

 408 and later again on day 502 (see Table IV). This slight increase 

 enabled the cow to begin to retain nitrogen. Reference to Tables \\ and 

 V shows that the rate of storage, however, was not very considerable 

 until within three or four weeks of partTirition. During this time, al- 

 though the amount of nitrogen excreted in tlic faeces remained roughly 

 at its former level, yet tiie nitrogen ajjpearing in the urine underwent a 

 marked diminution. This was a consequence of protein-retention. Ex- 

 amining the period as a whole, it would appear that the demands made 

 on the food protein for the single purpose of foetal development were 

 relatively small, since the average rate of nitrogen-retention was only 

 about 2-4 gm. per day. 



The behaviour of Cow C, dry and not in calf, during this period con- 

 trasted curiously with its behaviour in the preceding period, when it 

 was able to make a distinct gain of protein and body-weight. In this 

 period, though receiving approximately the same ration, Cow C suffered 

 a slight loss of protein and its weight dropped about 18 lb. These results 

 serve to illustrate further the uncertainty of short period work with 

 animals. 



Comments on Table V (Third Main Period of the Experiment). 



In Table V are given the full experimental details for the period im- 

 mediately preceding and following the calving of Cow D. Particulars of 

 mUk-yield, etc., for this and the following period will be found in Table 

 VIII. For some days after parturition, each day's collections of urine, 

 faeces and milk from Cow D were analysed separately. 



' A'meriran Journal of Phii.noloqii, 1910, xxvii 177. 



