THE CHEMISTRY OF THE ANIMAL BODY. 993 



account of the strong acid radical, passes through carnivora unchanged, but in 

 herbivora, the blood of which is more strongly alkaline, a certain part of the 

 ammonia is converted first into carbonate and then into urea. This conversion 

 of ammonium carbonate into urea is of striking interest. Artificial irrigation 

 of a liver with blood containing ammonium carbonate increases the urea in 

 the blood, while similar treatment of muscle or kidney shows no such results. 1 

 In other experiments it has been shown that ammonium salts appear in the 

 urine after feeding acids to carnivora, and that in disease in which acids are 

 produced (lactic, aceto-acetic, oxybutyric acids) ammonia accompanying them 

 is found in the urine, in all cases representing that ordinarily converted into 

 urea. In disease of the liver (cirrhosis, phosphorus-poisoning) ammonia is 

 found in the urine above the normal. Admitting the fact that ammonium 

 carbonate (and carbamate likewise) may be converted into urea by the liver, 

 there is no ground for believing that this is the normal process for the produc- 

 tion of the whole amount of urea, nor is there at present any measure of the 

 amount of ammonium-salts produced in the body. The liver may be very 

 completely destroyed by disease, and large quantities of urea still be excreted. 2 

 In geese extirpation of the liver has no effect on the urea excreted, therefore in 

 geese it is formed elsewhere. 3 For aught that is known, therefore, urea may 

 be formed in other organs than the liver, and it is not at all improbable that 

 it is formed in all organs where proteid decomposition is .progressing. The 

 greater part of urea from proteid is eliminated in the dog fourteen hours after 

 his meal (see p. 987). 



NET 



Guanidin, HN : C < *' ^ s ^ s *^ e i m ^ e f urea > an d has been obtained by the 



NH' 



oxidation of guanin. It unites with alcohol and acid radicals forming, for example, 



NTT NTT 



meth}'! guanidin, HNC < NHbH ' an( ^ S uan idin acetic acid, HN < NHCH COOH 



NH 



Creatin, or Methyl Guanidin Acetic Acid, HNC < AT//STT \nrr nr\r\-rr 



JN (^>H 3 jO ji 2 v_AXJxl. 



Creatin is a product of proteid decomposition and found in muscle to the ex- 

 tent of 0.3 per cent., in traces in the blood, and in varying amounts in the 

 urine. It is the principal constituent of meat-extracts (Liebig's). Creatin 

 may be formed synthetically by the union of cyanamide with sarcosin, and it 

 may be broken up into these constituents by boiling with barium hydrate, but 

 the cyanamide is immediately converted into urea through the addition of 

 water : 



H 2 N.CN + HNfCH^C^COOH = HN :C < 



Cyanamide. Sarcosin. Creatin. 



Creatin, however, is not converted into urea in the body if fed, but is ex- 

 creted in the urine as creatinin. 4 The amount of creatinin found in the urine 



1 Von Schroeder : Archivfilr exper. Pathologic und Pharmakologie, 1882, Bd. 15, p. 364. 

 * Marfort : Ibid., 1894, Bd. 33, p. 71. 

 8 Minkowski: Ibid., 1886, Bd. 21, p. 62. 

 4 Voit : Zeitschrift fur Biologic, 1868, Bd. 4, p. 114. 

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