This is the first volume of a series on normal serum. The second volume will treat of the physiologic characteristics of serum and subsequent ones of the chemical. Much confusion has been caused because in the past certain authors have considered the words plasma and serum as equivalent. In this work the word serum is applied only to the fluid that exudes naturally after the clotting of the blood. And normal serum is the serum of an animal in good physiologic equilibrium not subjected to immunizing injections. The present volume deals with the collection and physical characters of normal serum. The collection of serum from the horse, man and other species, and its conservation, aging and putrefaction are described in detail. Then follow chapters on the physical properties—density, osmotic pressure, electrical conductivity, dialysis, ultrafiltration, electrodialysis, surface tension, viscosity, refractometric index, rotatory power, color, spectroscopy. Each chapter is complete by itself,