Mice killed shortly after receiving c. 2000 spores of a type E strain of Clostridium botulinum per os were incubated at one of five chosen temperatures together with bottles of cooked meat medium seeded with a similar inoculum. After incubation the rotting carcasses were homogenized. Sterile membrane filtrates of the homogenates (10%, w/v) and pure cultures were then titrated for toxicity. Some of the main findings were confirmed with two further type E strains.

Toxicity produced at 37 °C was poor in both carcasses and cultures (200–20000 mouse intraperitoneal LD/g or ml). It was good in both systems at 30 and 23 °C, usually reaching 20000–200000 LD/g or ml, and in carcasses occasionally more; at 30 °C maximal toxicity was reached more quickly in carcasses than in cultures. Prolonged incubation (36–118 days) at 30 or 23 °C resulted in complete loss of toxicity in virtually all carcasses but not in cultures. At 16 °C the development of toxicity in carcasses was strikingly greater than in cultures. At 9 °C neither system produced more than slight toxicity after prolonged incubation. Trypsinization increased the toxicity of cultures but not usually of carcasses. Unfiltered carcass homogenate (10%, w/v) with maximal intraperitoneal toxicity was harmless for mice by mouth in doses of 0·25 ml. These findings differed in important respects from those made earlier with a type C strain.