CONJUGATED EXCRETA 



557 



It will be seen that despite the great increase of hippuric acid excre- 

 tion induced by these large dosages of benzoic acid the total daily 

 nitrogen elimination was unaffected. Evidently body-protein was not 

 attacked to provide the glycocoll needful for the synthesis of the hip- 

 puric acid. The glycocoll was evidently derived at the expense of the 

 urea-fraction, and the endogenous catabolism, in so far as it is repre- 

 sented by the creatinine output, remains unaffected. On the other 

 hand the acidosis induced by hydrochloric acid resulted in a large 

 increase of the total nitrogen output, the chief part of the increase 

 being Ammonia which performs the protective function of neutralizing 

 a part of the excess of acid. The urea and creatinine output were alike 

 unaffected by the administration of the acid. 



The glycocoll moiety of hippuric acid must therefore be traced to 

 the same origin as urea, and this, it will be remembered, is the amino- 

 acids of the tissue-fluids. No less than thirty-five per cent, of the 

 nitrogen of the food may be excreted as hippuric acid, and no protein 

 contains this percentage of glycocoll. It is evident that glycocoll may 

 be synthesized from other amino-acids. It might be imagined that 

 the benzoic acid unites with other amino-acids which thereafter under- 

 go partial oxidation until only the residue of glycocoll is left. Injec- 

 tion of such compounds synthetically prepared, however, leads to no 

 increase in the hippuric acid output. It seems probable, therefore, 

 that glycocoll may form a normal disintegration-product of many 

 amino-acids, that under ordinary circumstances it is finally deaminized, 

 but that when toxic substances that will pair with it, namely aromatic 

 acids, are present in the tissue-fluids, deaminization is prevented by 

 the conjugation. 



The power of the tissues to synthesize glycocoll is of very great 

 importance, since it not only enables the body to protect itself against 

 such poisons as benzoic acid, but also enables suckling animals to 

 synthesize their tissue-proteins from a protein which is totally lacking 

 in glycocoll, namely the casein of milk. 



When the administration of benzoic acid is pushed beyond the 

 limit of the glycocoll available from the proteins of the diet the protec- 

 tive mechanism breaks down and free benzoic acid appears in the 

 urine. Under no circumstances, it appears, are tissue-proteins attacked 



