*286 PATHOGENIC BACTERIA. that a temperature of 58° C. for ten minutes is fatal to it. Notwithstanding this susceptibility, the organism can be kept alive for several weeks after being dried upon shreds of silk or when surrounded by dried diphtheria membrane. No flagella have been demonstrated upon the bacillus. It is non-motile. Fernbach has shown that when the organisms are grown in a medium exposed to a passing current of air, the luxuriance of their development is increased, though their life-cycle is shorter. The growth can also take place when the air is excluded, so that the bacillus must be classed among the optional anaerobic organisms. The diphtheria bacillus grows readily upon all the ordinary media, and is a very easy organism to obtain in pure culture. Loffler has shown that the addition of a small amount of glucose to the culture-medium increases the rapidity of the growth, and suggests a special medium which bears his name—Loffler's blood- serum mixture: Blood-serum, 3; Ordinary bouillon + i per cent, of glucose, i. This mixture is filled into tubes, coagulated, and steril- ized like blood-serum, and is one of the best-known media in connection with the study of diphtheria. The studies of Michel1 have shown that the develop- ment of the culture is much more luxuriant and rapid when horse serum instead of beef or calves' blood is used. Horse's blood can easily be secured by the introduction of a trocar into the jugular vein ; 5 liters of it can be with- drawn without causing the animal any inconvenience or producing symptoms. The impossibility of clinically making an accurate di- agnosis of diphtheria without a bacteriologic examination has caused many private physicians and many medical societies and boards of health to equip laboratories where 1 Centralbl.f. Bakt. u. Parasitenk., Sept. 24, 1897, Bd. xxii., Nos. loand II.