The distribution of nitrogen and sulphur in the urine during conditions of increased catabolism

As the result of a series of analyses of the urine of normal subjects on standard diets of varying nitrogen and sulphur content but practically free of purine, creatine and creatinine, Folin [1905] advanced the hypothesis that there are two essentially different forms of protein catabolism, the constant or endogenous catabolism yielding chiefly creatinine and neutral sulphur and to a less extent uric acid and ethereal sulphates, and the variable catabolism yielding chiefly urea and inorganic sulphates. Folin stated that "the more the total catabolism is reduced the more prominent become these represen- tatives of the constant catabolism, and the less prominent become the two representatives of the variable catabolism." Whilst Folin's general hypothesis has been accepted, doubt has been ex- pressed as to whether these various excretory products can be exactly divided into two such groups.