CHEMICAL SCIENCE. 337 



itself in the blood of animals after the removal of the kidneys, and that 

 they conclude from the fact that the kidneys remove the urea, while not 

 producing it. 



M. Picard has completed the demonstration. He has compared, as re- 

 gards the presence of urea, the arterial and venous blood by precipitating 

 the urea with nitrate of mercury. The renal artery of a dog afforded 0'03G5 

 per cent of urea, and the renal vein only 0-0186 per cent. In studying the 

 question with reference to man, he has observed that the arterial blood 

 winch passes into the kidneys leaves there about twenty-eight grams of urea; 

 while the quantity of urea in the urine of the subjects submitted to experi- 

 ment, varied between twenty-seven and twenty-eight grams for the twenty- 

 four hours. This proves that the kidneys remove but do not make urea, as 

 announced thirty-five years since by Pre'vost and Dumas. 



ON UREA AS A DIRECT SOURCE OF NITROGEN IN VEGETATION. 



At the Dublin meeting of the British Association, Professor Cameron 

 showed that nitrogen was as available as food for plants, when a constituent 

 for urea, as in its ammoniacal combination ; or, in other words, that urea, 

 without being converted into ammonia, may be taken up into the organisms 

 of plants, and there supply the necessary quantity of nitrogen. He des- 

 cribed the experiments which led him to this conclusion, which Avere very 

 elaborate, and were made on barley plants, in circumscribed spaces, and 

 where the air was, in consequence of being treated Avith dilute sulphuric 

 acid, rendered free of ammonia, the barley having been sown in a soil 

 Avhich Avas constituted of felspar, and an artificial manure, containing sub- 

 stances derived from the ashes of the barley plant. To some of the earthen 

 vessels in Avhich the barley was planted urea Avas supplied, and to others 

 sulphate or ammonia, and some Avere left Avithout any nitrogeneous matter 

 Avhatever. In the two former instances the results were equal they both 

 arrived at maturity simultaneously and the ears AA r ere equally developed. 

 The instances in Avhich no nitrogenous substance Avas used merely germin- 

 ated, small stems appeared, but no curs Avere produced. The deductions 

 from the foregoing Avere thus enumerated by Dr. Cameron, 1. That 

 the perfect development of barley can take place, under certain conditions, 

 in soil and air free of ammonia and its compounds. 2. That urea in 

 solution is capable of being taken into the organism of plants. 3. That 

 urea need not be com-erted into ammonia before its nitrogen becomes avail- 

 able to promote the process to serve the purposes of A-egetation. 4. That 

 the fertilizing effects of urea are little, if at all, inferior to those of am- 

 moniacal salts. 5. That there exists no necessity for al 'curing drainings or 

 other fertilizing substances containing urea to ferment, l:iit on the contrary, 

 greater benefits must be derived from their application in a fresh or unfer- 

 mented state. 



FUNCTION OF SALT IN AGRICULTURE. 



Mr. A. B. Korthcote has communicated to the London Philosophical 

 Magazine, a paper of experiments undertaken to ascertain the rationale of 



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