In Table 3, creatinine clearance in dogs was increased after the meal of meat and in following chapters increase in glomerular filtration rate will be seen as a major factor determining increased excretion of urea, SO4, PO4 and possibly K. In discussing Na excretion (Chapter 8) the main argument revolves around the probable role of a small increase in glomerular filtration as a mechanism determining increased excretion of Na. Glomerular filtration rate is central to renal function.