222 PATHOGENIC BACTERIA. 



The diphtheria bacillus does not form spores, and is 

 delicate in its thermal range. L,6ffler found that it could 

 not endure a temperature of 60 C., and Abbott has shown 

 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 LofHer'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 clinical impossibility of making an accurate diag- 

 nosis of diphtheria without a bacteriologic examination 

 has made many private physicians and many medical 

 societies and boards of health equip laboratories where 

 accurate examinations can be made. The method re- 

 quires some apparatus, though a competent bacteriologist 

 can often make shift with a bake-oven, a wash-boiler, 

 and other household furniture instead of the regular 

 sterilizers and incubators, which are expensive. 



