The Use of Pancreatic Extract as a Growth Stimulant for C. Diphtheriae.

mer, had a markedly stimulating effect on the growth of C. diphtheriae and that they retained this power even after the digestive enzyme content had been inactivated by heat. The active principle in the pancreatic extract is water-soluble, passes readily through a collodion membrane, and is thus of low molecular weight. Further investigations were undertaken to determine whether pancreatic extract could with any advantage be incorporated in some of the blood tellurite media commonly used for the isolation of C. diphtheriae. The heated blood tellurite agar of Anderson et al. (1931) prepared with low temperature meat extract gives excellent type differentiation but is at a disadvantage when certain haematin-sensitive mitis and gravis strains (Glass, 1937; Robertson, 1943) are encountered. This difficulty is overcome by using unheated instead of heated blood (Glass, 1937). Hoyle's (1941) tellurite medium, though not suggested specially for haematin-sensitive strains, permits their growth