The disease syndromes produced by both Bacillus anthyacis organisms and by sterile in vitro toxins are orderly and predictable. Most of the signs and changes in the blood cellular, chemical, and gaseous elements occur late in the septicemic phase of disease, whereas similar changes occur earlier after administration of toxins. The only pathophysiological response peculiar to any of the 3 species of animals used in this study (rhesus monkey, chimpanzee, and rabbit) was the presence of nucleated red blood cells in the rabbit and the absence of these cells in the 2 primates. All effects appeared to be nonspecific and included elevation of white blood cells with a marked shift to the left, decreased calcium, sodium, and cholinesterase, and increased potassium, chloride, and phosphate. Hyperesthesia frequently was observed, and late in the course of disease a terminal hypoglycemia with alkalosis and hypoxia occurred. One of the most significant observations was failure of the body to respond to the organisms per se but rather to the toxins of B. anthyacis.