984 AN AMERICAN TEXT-BOOK OF PHYSIOLOGY. 



leucin (and tyrosin) appear in the urine, which may be interpreted to mean that 

 these substances, normally produced from proteid metabolism in the tissues, are 

 not normally burned but accumulate within the body, and are excreted (see 

 below). 



Another view, advanced by Von Noorden l and based on the unconfirmed experiments of 

 Harris and Tooth, 2 claims that leucin and tyrosin are not found in tryptic digestion if bac- 

 teria be excluded. Leucin and tyrosin are found in yellow atrophy of the liver both in the 

 urine and in the liver itself, under conditions indicating their production by bacteria and 

 their non-combustion after production. In phosphorus-poisoning and acute anaemia leucin 

 and tyrosin occur in the urine, but apparently without good ground for considering them 

 of bacterial origin. Von Noorden argues that, as in yellow atrophy of the liver, the tissue- 

 cells have become incapable of decomposing leucin and tyrosin, and these substances 

 absorbed as products of intestinal putrefaction cannot be burned but are eliminated by the 

 urine. That leucin is a product of proteid metabolism in the tissues has never been shown. 



Leucin crystallizes in characteristic ball-shaped crystals. It was formerly supposed to 

 be amido-caproic acid, but Schulze 3 has shown its true composition. Inactive leucin con- 

 sists of a mixture of d- and ?-leucin, and may be obtained by treating conglutin with 

 Ba(OH) 2 . The two leucins maybe separated by fermentation of d-leucin with Penidllium 

 glauciim. Cleavage of proteid by acids and by putrefaction seems to yield d-leucin. 4 



Caprylic, C 8 H 16 O 2 , and Capric, C 10 H 20 O 2 , Acids. These are found as 

 glycerin esters in milk-fat. They are likewise present in sweat and in cheese. 



Palmitic, C 16 H 32 O 2 , and Stearic, C 18 H 36 O 2 , Acids. As glycerin esters 

 these two acids are found in the ordinary fat of adipose tissue, and in the fat 

 of milk. The acids may occur in the feces, and are found combined with 

 calcium in adipocere (p. 1002). Wool-fat consists in the cholesterin esters of 

 these acids. 



The bile contains palmitic, stearic, and oleic acids, 5 and to these have been 

 attributed its very slight acid reaction. 6 



COMPOUNDS OF THE ALCOHOL RADICALS WITH NITROGEN. 



Amines. These are bodies in which either one, two, or three of the hydrogen atoms 

 in ammonia are replaced by an alcohol radical, and are termed respectively primary, second- 

 ary, and tertiary amines. Methyl, ethyl, and propyl amine bases are the products of pro- 

 teid putrefaction. They resemble ammonia in their basic properties. 



Methylamine, NH 2 (CH 3 ). This is found in herring-brine. It has the fishy smell 

 noted in decaying fish. It is a product of the distillation of wood and of animal matter. 

 Feeding methylamine hydrochloride is said to cause the appearance of methylated urea in 

 a rabbit's urine 7 (analogous to the formation of urea from ammonia salts) : 

 2HC1.NH 2 (CH 3 ) + C0 2 = OC(NHCH 3 ) 2 + 2HC1 + H 2 0. 



According to Schiffer, 8 the body, probably through intestinal putrefaction, has the power 

 of partially converting creatin into oxalic acid, ammonia, carbonic acid, and methylamine, 

 which last is finally excreted as methylated urea in the urine. 



V 



- 1 Pathologie des Sto/wechsels, 1893, p. 296. 2 Journal of Physiology, 1888, vol. 9, p. 220. 



3 Berichte der deutschen chemischen Gesellschaft, 1891, Bd. 24, p. 669; also, Gmelin : Zeitsehnft fiir 

 physiologische Chemie, 1893, Bd. 18, p. 38. 



4 Gmelin: Zeitschrifl fiir physiologische Chemie, 1893, Bd. 18, p. 28. 



5 Lassar-Cohn : Ibid., 1894, Bd. 19, p. 571. 



8 Jolles: Pfliiger's Archiv, 1894, Bd. 57, p. 13. 



7 Schiffer: Zeitschrift fiir physiologische Chemie, 1880, Bd. 4, p. 245. 8 Loc. cit. 



