The Excretion of Inulin by the Dog

The present paper reports observations on the excretion of the polysaccharid inulin by the normal and phlorizinized dog, these observations having been made prior to, or concurrently with, the observations on man recently reported by Shannon and Smith (1935). The introduction of inulin in renal function studies has been discussed by Richards, Westfall and Bott (1934), by Shannon (1934), by Professor Richards in his 1935 Harvey Lecture, and by Shannon and Smith in the above paper, and this discussion need not be extended here. CHEMICAL METHODS. The chemical methods used in this investigation were the same as those described by Shannon and Smith (1935), except that in some of the earlier experiments sugars were determined both on a copper sulphate-sodium tungstate filtrate (Somogyi, 1931) by the Folin (1929) sugar method, as well as on the iron filtrate of Steiner, Urban and West (1932) by the Shaffer-Somogyi (1932) method. Extensive observations on recovery of inulin, glucose and xylose from plasma and urine have been made with both methods. The Folin method gives incomplete reduction with xylose but when plasma and urine are handled alike one should obtain the same U/P ratio by this as by the Shaffer-Somogyi method, especially since the saccharoid blank is low with both methods of precipitation (2 to 3 mgm. per cent with the copper and 1 to 2 mgm. per cent with the iron). Nevertheless, in experiments where both methods have been used, it has been observed that the Shaffer-Somogyi method gave values for the xylose clearance averaging five per cent lower than by the Folin method, although the inulin and glucose clearances by the two methods were identical. The reason for this discrepancy is not revealed