I. Infection and body resistance have been studied from various angles for several centuries. Empirically, nonspecific therapy has been practiced in different forms for an equal period of time, and only of late has scientific endeavor been applied to solve the problems to which the uses of such agents have given rise. Petersen1 has particularly emphasized the rôle that body resistance plays in the administration and the results of nonspecific treatment. Our aim has been to determine the physiologic basis of this resistance; in other words, to point to certain organs whose common functions were practically synonymous with resistance. We believe that resistance is a product of the functions of various organs, and it is quite probable that these organs possess additional functions that are exercised normally in the course of biologic processes. The functions of resistance are normally inherent in the body but, under healthy conditions, their activity is