SUMMARY.Differential responses occurred in the amount of urea nitrogen and total nitrogtsn secreted in the parotid saliva, according to the nitrogen status of the sheep, when 1-4 gm. of urea nitrogen was injected into the hlood daily. Of this amount of nitrogen, 01 gm. could be recovered in the secretion from one parotid gland daily when the sheep were in positive nitrogen balance, and 0-3 gm. when the sheep were in negative nitrogen balance.The urinary excretion accounted for 1-0 gm. of the 1-4 gm. of urea nitrogen injected daily when the sheep were in positive nitrogen balance, but only 0-3 gm. per day at the lower nitrogen status.The implications of these findings were discussed in relation to a urea conservation mechanism in sheep.INTRODUCTION.

SUMMARY.Measurements were made on the distribution of nitrogen in the mixed and parotid salivary secretion of sheep and on the amount of nitrogen secreted daily in the parotid saliva.The distribution of nitrogen in the mixed saliva followed the same pattem as that in the parotid secretions obtained when the glands were in a quiescent state. The concentration of nitrogen in botli fluids depended on the rate of secretion.Although the concentration of total nitrogen in the mixed and parotid saliva increased during short-term stimulation, tlie pattern of nitrogen distribution was not affected. During prolonged stimulation of the parotid glands the nitrogen composition of the saliva changed.Quantitatively, urea was the most important nitrogtn conipoiind in both the mixed and parotid saliva, accounting for 60-70 p.c. of the total nitrogen.The average volume of saliva secreted daily by one parotid gland was 2380 ±43-8 ml. and the average total nitrogen content was 295-5 ±5-77 mg. when the nitrogen intake was 14'8 gm. per day.Some implications of the amount and nature of the nitrogen compounds in relation to the niminal metabolism of nitrogen iu sheep are discussed.INTRODUCTION.

SUMMARY.Urea was added to the rumen of three merino sheep at the rates of 5, 10 and 20 gm. daily to increase the overall nitrogen intakes from 10-7 gm. in the basal ration to 13-0, 15 4 and 20-0 gm. per day.A marked increase in the total amount of nitrogen secreted in parotid saliva was found to occur as the nitrogen intake of the sheep rose. A similar high correlation was found hetween the level of nitrogen intake and the amount of urea nitrogen secreted in the saliva daily.Between the highest and the lowest levels of nitrogen intake the magnitude of the increases were 0-26 gm. of total nitrogen and 0-18 gm. of urea nitrogen per gland per day.The concentration of urea nitrogen in the blood increased with the level of nitrogen intake of the sheep, but fluctuations in the level of blood urea could not be accounted for by nitrogen intake alone.A significant correlation was found between the concentrations of urea nitrogen in the blood and in the saliva. This offered a partial explanation of the higher concentrations of salivary urea resulting from the increased nitrogen intakes.INTRODUCTION.