550 AN AMERICAN TEXT- BOOK OF PHYSIOLOGY. 



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 alter feeding acids to carnivore, and that in disease in which acids are 

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

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

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

 found in the urine above the normal. If the liver be excluded from the 

 dog's circulation by Eck's fistula, ammonium salts accumulate in the blood. 

 If an amido body like ijlycocoll be i'vA to such a dogr, ammonium salts 

 rapidly accumulate, which indicates the normal fate of glycocoll. 2 .Amido 

 acid-, such as glycocoll, leuein, etc., which arc cleavage products of proteids, 

 and which are known to burn to urea, are nevertheless highly resistant to 

 strong chemical reagents, either alkalies or acids. Lewi's 3 work indicates 

 that a ferment present in the liver (and perhaps elsewhere) may convert these 

 stable compounds into others in which the nitrogen is less (irmly combined, 

 which may in turn be converted into urea. 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. 4 

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

 geese it is formed elsewhere. 5 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. 544). 



Guanidin, HN:C<Cmtt". This is the imide of urea, and lias been obtained by the 

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

 methyl guanidin, HNC <C vii'Jut • au, l guanidin acetic acid, HN <C Kiihxj POOTT 



Creatin, or Methyl Guanidin Acetic Acid, HXO < ^//-iVr \nxj POOTT 



( Veatin 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 (Liobig'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 : 



1 Von Schroeder : Archiv fur exper. Pathologie mi, I Phnrmakohigic, 1882, Bd. 15, S. 3(i4, 

 - Salaskin, 8. : Zeitschriftfiir physiologische Chemie, L898, Bd. 25, S. 449. 

 8 Zeit&chrift Jur physiologische Chemie, L898, Bd. 25, S 511. 

 1 Marfort: Archiv fur exper. Pathologie mi, I Pharmakokgie, 1894, Bd. 33 S. 71. 

 Minowski: Ibid., 1886, Bd. 21, 8.62. 



