688 ANIMAL PHYSIOLOGY, 
water and in ether; lessso in alcohol. Creatin may be changed into 
urea and sarcosin or methyl-glycin: 
C.H»N;:0, + H:O = CsH;NOs + CON: Hy. 
Creatin. Sarcosin, Urea. 
It may also be formed synthetically under the action of acids. Creatin 
may by dehydration be transformed into creatinin. 
Creatinin. C.H,N.O. 
-This body may be regarded as dehydrated creatin. It occurs nor- 
mally in flesh and urine, and may be obtained in prisms; soluble in 
‘water and alcohol, but not appreciably in ether. It acts as a strong 
base, the most important salt being the zinc chloride (C.H,NsO).ZnCh. 
Allantoin. C.H.N.Os.. 
A body characteristic of the allantoic fluid of foetal life, and which 
may occur in the urine. Its relations to uric acid and urea have been 
indicated above. 
Hypoxanthin (sarkin). CsH.N.O. 
Occurs in fiesh, in the spleen, liver, medulla of the bones, etc. ‘It 
may be obtained in fine needles, soluble in hot water. 
Xanthin. CsHiNiOn. 
May be derived from muscles, the liver, spleen, thymus, and some 
other organs and tissues. It is probably a normal constituent of the 
urine in minute quantity. It may be obtained as a colorless powder,, 
only slightly soluble in water, but soluble in dilute acids and alkalies. 
Xanthin may be regarded as the oxidized form of hypoxanthin. 
Carnin. C,H:N.Os. 
Occurs in extract of flesh, and may be obtained in crystals, insoluble 
in aleohol and ether, but slightly soluble in cold water, and more so in 
hot water. 
Guanin. C;H;N.O. 
So called because first obtained from guano (excrement of birds); it 
is. however, also to be extracted from several organs and tissues; asa 
white amorphous powder, insoluble in water, alcohol, ether, etc. By 
treatment with nitrous acid it may be converted into xanthin. 
Kynurenic acid. C.oHisN2Os. 
This body has been found in the urine of dogs. 
Glycin. (Glycocoll, glycocin, amido-acetic acid.) CsHsNOs:, or 
/NHe 
CH: 60. 
This is one of that important class of compounds, the amido-acids, 
and may be formed in the laboratory from mono-chlor-acetic acid and 
ammonia: 
C:H;Cl0. + 2(NHs) = C2H2(NH:)O(OH) + NH.Cl. 
It is peculiar in having both acid and basic properties—i. e., it unites 
with both acids and bases to form crystallizable compounds. Glycin 
itself may be obtained in crystalline form soluble in water. Though 
