42 J Sfiidji of Nitroijen Metabolism, in tin Dairy Con- 



111 all changes of feeding a transitional period of at least nine days 

 was allowed, whilst the experimental period consisted of at least twelve 

 days, giving a minimum period of three weeks between each change. 

 The essential data obtained are summarised in Table T. 



Table I. 

 Cow A. (Initial weight. W?,^ II).) 



* The concentrated food diirini; this period consisted of 91b. maize + 1 lb. linseed cake. 



The investigation proceeded quite smoothly up to Period V, when it 

 became necessary to draw a fresh consignment of hay. This proved un- 

 fortunately to be decidedly poorer in nitrogen than the previous con- 

 signment, and conse(|uently, despite the added 2 lb. of maize, the nitro- 

 gen consumption for Period V worked out rather less than for Period IV. 

 In order to overcome this difficulty the basal ration of hay was increased 

 for Period VI to 16-5 lb. per day, the maize meal being retained as in 

 Period V at 81b. Unfortunately, although Cow A consumed the increased 

 ration of hay satisfactorily, Cow B could not be induced to do so, and in 

 consequence this cow had to be kept for the remainder of the experiment 

 on the lower ration (14 lb.) of hay, so that from this point the records 

 of the two cows were not strictly comparable. 



Further difficulty was experienced towards the end of the experiment 

 in inducing the cows to consume the rations completely and it was ob- 

 vious that we were approaching the limits of their ajipetitcs. This was the 



