ITS ABNORMAL CONSTITUENTS. 429 



Butyric add, which was first detected in the urine by Berzelius,* 

 is only rarely present in it either in health or disease. The occur- 

 rence of this acid does not seem to be associated with any definite 

 form of disease ; I have more frequently met with it in the urine 

 of pregnant women than in that of non-pregnant women, or men. 



Berzelius submitted to distillation urine that had been treated 

 with sulphuric acid, saturated the acid distillate with baryta water, 

 filtered, and obtained on evaporation a crystalline saline mass, 

 which, on the addition of sulphuric acid, developed much butyric 

 acid. On repeating the experiment, and submitting very large 

 quantities of urine to such treatment, I never obtained more than 

 traces of butyric acid ; but on examining the urine of a woman 

 who was not suckling (who was living on very low diet, and had 

 little appetite), on the third, fourth, sixth, and ninth days after de- 

 livery, I obtained, by merely extracting the solid residue with 

 ether, an acid fat which had the odour of butyric acid, and exhibited 

 the ordinary properties of that substance : on then dissolving in 

 water the residue that had been extracted with ether, adding sul- 

 phuric acid, and following the directions of Berzelius, I obtained a 

 fresh quantity of butyric acid. This urine which contained butyric 

 acid was always somewhat turbid and of a dirty yellow rather than 

 an amber colour. 



Ammoniacal salts, such as the hydrochlorate of ammonia, phos- 

 phate of soda and ammonia, and phosphate of magnesia and am- 

 monia, do not occur in fresh urine, although their presence there 

 has been often asserted. The experiments which prove the non- 

 existence of ammonia in fresh urine have been described in p. 452 

 of the first volume. We have there also remarked that the 

 efflorescence which is observable on evaporating a drop of urine 

 under the microscope, depends neither upon hydrochlorate of 

 ammonia, or phosphate of soda and ammonia. When, on the 

 other hand, ammonia can be distinctly recognized in fresh urine 

 after its evaporation, it must be the product of some decomposition. 

 We have already alluded to the facility with which urinary pigment 

 undergoes alteration, and thus hastens the decomposition of the 

 urea. Any one, by repeating the following experiment which I 

 devised, may readily convince himself that the presence of ammonia 

 in even the most carefully evaporated urine affords no proof of its 

 presence in the fresh secretion ; for if we evaporate perfectly fresh 

 urine in a retort at the lowest possible temperature, we always find 

 ammonia in the distillate, while the concentrated urine that is left 

 * Lehrb. d. Ck. Bd. 9, S. 424. 



