The term "normal urine" has conveyed different meanings as it has been employed by writers in the last fifty years, since more or less exact analyses of the excretion have been available, and even to-day a comparison of the clinical literature, on the one hand, with the special research literature, on the other, would show a very great lack of harmony in the use of the term.
For one class of writers, by no means small, the conception of a normal urine was apparently that of an excretion from healthy individuals consuming a rather large weight of food in nearly constant quantity from day to day; the important products in the excretion were supposed to appear in proportions varying within pretty narrow limits. This old idea grew up at a time when our notions of the protein metabolism were rather obscure, and when foods in general and the proteins in
LONG JH. THE DEFINITION OF NORMAL URINE. JAMA. 1912;LVIII(11):757-760. doi:10.1001/jama.1912.04260030155009