The third, and central, chapter of this book is a new chapter in the balance study of surgical patients. Nine neonatal patients are presented in detail as regards their daily hemoglobin, hematocrit, blood urea, plasma alkaline reserve, plasma chloride, plasma sodium, plasma potassium, plasma protein, red cell nitrogen, red cell chloride, red cell sodium and potassium, weight, and eosinophil count, all of which are presented in nine tables. Bar graphs are used similar to those of Albright and Reifenstein and Moore and Ball, showing intake, output, and net gain or loss of water, nitrogen, chloride, sodium, and potassium. Single initial measurements of the distribution space of T1824, sodium thiosulphate, and N-acetyl-4-amino-antipyrine were made in four patients. Each case is presented in detail and discussed. All of this is then briefly summarized at the end of the chapter. Current and historical work on the metabolism of infants and the response of