C. Crowthbr and H. E. Woodman 45 



water a still higher degree of completeness could, be obtained in the 

 recovery of urinary nitrogen. 



E.rpni'mcntal detail.';. 



Collection, Sampling and Analysis of Faeces. The faeces were collected 

 into weighed covered buckets. The 2-i-hours' collection was weighed, 

 thoroughly mixed, and by quartering, reduced to a small sample. One- 

 tenth of the daily faeces was preserved in a closed vessel with the 

 addition of a little toluene. In this manner, composites were made up 

 twice weekly, representing the collection over three and four days respec- 

 tively. Preliminary tests had shown that the loss of nitrogen was inap- 

 preciable when the faeces were stored in this manner over a period of 

 several days. The composite samples were well mixed and small samples 

 were drawn from the bulk for analysis. The nitrogen-content was deter- 

 mined in triplicate by means of the Kjeldahl method. 



Collection, Sampling and Analysis of Urine. The urine was collected 

 in weighed buckets, the drainage being assisted by frecjuent spraying of 

 the floors with water. No litter was used in the stalls. The daily output 

 of urine was weighed and, after thorough stirring, one-tenth of the total 

 weight was ladled out, acidified with 20 c.c. H0SO4 (1:1) and preserved in 

 a Winchester bottle. Composites were made up in this way twice weekly 

 and the nitrogen-content of the samples was determined by the Kjeldahl 

 method. Under the conditions of collection the faeces were always con- 

 taminated with urine, and the urine was diluted to some extent by the 

 water used in spraying. This was immaterial, however, as it was only 

 required to measure the total voided nitrogen. 



Length of periods and 'weighing of cows. The jseriods were mainly 

 of about 18 days' duration. At the end of each period the cows were 

 weighed on three successive days under comparable conditions. 



Feeding of cows and analysis of foodstuffs. The hay was fed in four 

 equal allowances during the day, care being taken that the cows had 

 consumed the hay completely before being left for the night. Water 

 was given ad lib. Composite samples of the feeds were made up by 

 reserving weighed representative samples daily. Two independent hay 

 composite samples were made up in each period, and the dry matter and 

 nitrogen-contents of these were determined, the mean results for the 

 two samples being used in the calculation of the nitrogen-balances. 

 From time to time representative samples were made up from the period 

 composites and complete analyses were carried out. Moisture deter- 



