THE AROMATIC OXY-ACIDS. 285 



filtrate the lead is removed by means of hydrogen sulphide, and the 

 excess of the latter by gently warming on a water-bath. The 

 fluid is then concentrated to a thick syrup and extracted with ether. 

 The ethereal solution is evaporated and the residue boiled for some 

 time with water and an excess of zinc carbonate. The mixture 

 is filtered while hot, concentrated to a small volume, and then set 

 aside in the cold after adding a little alcohol. The zinc salts of 

 both paralactic acid and the common optically inactive lactic acid 

 which may also be present in traces, then crystallize out. They 

 can be separated from each other by treating with absolute alcohol, 

 in which the latter is insoluble. It must be noted that the solu- 

 bility of the paralactate is also slight (1 : 1100), so that it is 

 necessary to add a large amount of alcohol. In order to prevent 

 confusion with the aromatic oxy-acids of the urine, the lactate 

 crystals should now be further identified, which is most conveniently 

 done by estimating the water of crystallization. The paralactate 

 contains two molecules of this, which escapes at 105 C., and at this 

 temperature the weight of the crystals should therefore diminish 12.9 

 per cent, The salt, moreover," like its acid, is laevorotatory, while 

 the common lactate is optically inactive. 



Mono-amino Acids. 



Tyrosin, leucin, and glycocoll have long been known to occur in 

 the urine in acute yellow atrophy and phosphorus poisoning, but 

 aside from these conditions nothing further was known of the 

 presence of amino-acids under other pathological conditions (barring 

 cystmuria). Within recent years, however, and with more exact 

 methods it has been possible to show that bodies of this order 

 may occur under the most divers conditions. Phenyl-alanin, alanin, 

 and arginin have been found in phosphorus poisoning, besides 

 tyrosin, leucin, and glycocoll. Glycocoll, indeed, according to a 

 recent announcement by v. Noorden, is a normal constituent of 

 the urine and may amount to 1 per cent, of the total nitrogen sul- 

 phate. (This is in marked contrast to the statement of Ignatowski 

 that normal human urine only contains traces of amino-acids at 

 best, and that even after the subcutaneous injection of 6 grammes 

 of glycocoll none are demonstrable.) 



Abderhalden found tyrosin in a patient dying with pneumonia 

 who had been suffering from arteriosclerosis, myocarditis, and dia- 

 betes. In a second case of diabetes he likewise found tyrosin and 

 obtained a marked Millon reaction. In a third case with coma 

 tyrosin was present also during the attack, but absent in the interim. 

 In a case of severe hepatic cirrhosis a marked /9-naphthalin-sulpho- 

 chloride reaction occurred, but it was impossible to isolate amino-acids 

 in pure form. The same observer obtained tyrosin in a case of severe 

 icterus referable to complete occlusion of the common duct and in a 

 patient who had undergone prolonged narcosis ; both urines gave a 

 marked Millon reaction. 



