738 URINE. 



acid or any other intermediary product of the cleavage of tyrosine in 

 the urine after taking 150 grams /-tyrosine (of which 141 grams were 

 absorbed) . 



DAKIN 1 has recently opposed the above-mentioned view that in the 

 cleavage of tyrosine and phenylalanine, homogentisic acid is always 

 produced, and that the condition of alcaptonuria consists in an inability 

 of the body to burn this intermediary product of metabolism. He has 

 found that tyrosin-methyl ether, which cannot form any quinone-like 

 intermediary product, can in cats be just as completely burnt as tyrosine, 

 and the same is true for p-methylphenylalanine and for p-methoxy- 

 phenylalanine, which cannot form any quinone derivatives. Still 

 these substances can be completely burnt by alcaptonurics and accord- 

 ing to DAKIN the body in alcaptonuria has still the ability to completely 

 burn the aromatic nucleus of tyrosine and phenylalanine when the 

 transformation into homogentisic acid is prevented by a proper sub- 

 stitution in the para-groups. DAKIN therefore considers alcaptonuria 

 as a condition in which partly the formation of an abnormal metabolic 

 product the homogentisic acid takes place and where partly the ability 

 of the body to burn this product is diminished. 



GARROD, 2 who has observed several cases of alcaptonuria, has also 

 tabulated a large number of cases of alcaptonuria which he finds in the 

 literature, and he shows that the anomaly of the protein metabolism 

 occurs oftener in males than in females, and also that blood relationship 

 of the parents (first cousins) predisposes to alcaptonuria. 



On fusing homogentisic acid with alkali it yields gentisic acid (hydro- 

 quinone-carboxylic acid) and hydroquinone. When introduced into the 

 intestine of the dog a part is converted into toluhydroquinone, which 

 is eliminated in the form of an ethereal sulphuric acid. Homogentisic 

 acid has also been prepared synthetically by BAUMANN and FRANKEL, 

 starting with gentisic aldehyde, and by NEUBAUER and FLATOW 3 from 

 o-oxyphenylglyoxylic acid with hydroquinone glyoxylic acid and hydro- 

 quinone glycollic acid as intermediary bodies. 



Homogentisic acid crystallizes with 1 mol. of water in large, trans- 

 parent prismatic crystals, which become non-transparent at the tem- 

 perature of the room with the loss of water of crystallization. They 

 melt at 146.5-147 C., and are soluble in water, alcohol, and ether, but 

 nearly insoluble in chloroform and benzene. Homogentisic acid is 



1 Journ. of Biol. Chem., 8 and 9, with Wakeman, ibid., 9. 



2 Med. chirurg. Transact., 1899 (where all cases up to that time are tabulated); 

 also The Lancet, 1901 and 1902; Garrod and Hele, Journ. of Physiol., 33. 



3 Baumann and Frankel, Zeitschr. f. physiol. Chem., 20; Neubauer and Flatow., 

 ibid., 52. 



