BACTERIA PATHOGENIC TO MAN 



epidemic diphtheria. One year later, Loeffler published the results of 

 a very thorough and extensive series of investigations on this subject. 

 He found the bacillus described by Klebs in many cases of throat inflam- 

 mations which had been diagnosticated as diphtheria. He separated 

 these bacilli from the other bacteria present and obtained them in pure 

 culture. When he inoculated the bacilli upon the abraded mucous 

 membrane of susceptible animals more or less characteristic pseudo- 

 membranes were produced, and frequently death or paralysis followed 

 with characteristic lesions. 



In 1887-88 further studies by Loeffler, Roux, and Yersin added to the 

 proof of the dependence of diphtheria on this bacillus. It was found 

 that, while no other forms of bacteria were constantly met with, the 

 diphtheria bacilli were present in all characteristic cases of diphtheria, 

 and that these bacilli possessed the morphological, cultural, and patho- 

 genic qualities of those described by Klebs and Loeffler. The results 

 of these investigations have since been confirmed by a great number 

 of combined clinical and bacteriological observations both in animals 

 and human beings. 



Human Inoculation Experiments. A very instructive accidental ex- 

 periment was carried out under our observation some years ago. One 

 of the investigators unintentionally drew quite a quantity of a bouillon 

 culture of a virulent diphtheria bacillus into the throat, and two days 

 later characteristic diphtheria of a serious type developed. Similar 

 accidents have happened in two other laboratories. In view of known 

 facts, we are now justified in saying that the name diphtheria should be 

 applied, and exclusively applied, to that acute infectious disease usually 

 associated with pseudomembranous affection of the mucous membranes 

 which is primarily caused by the bacillus diphtheriae of Loeffler. 



Morphology. When cover-glass preparations made from the cul- 

 tures grown on blood serum are examined, the diphtheria bacilli are 

 found to possess the following morphological characteristics: The 

 diameter of the bacilli varies from 0.3 to 0.8/* and the length from 1 

 to Q/Ji. They occur singly and in pairs (see Figs. 74 to 81) and very 

 infrequently in chains of three or four. The rods are straight or slightly 

 curved, and usually are not uniformly cylindrical throughout their 

 entire length, but are swollen at the end, or pointed at the ends and 

 swollen in the middle portion. The average length of the bacilli in 

 pure cultures from different sources frequently varies greatly, arid even 

 from the same culture individual bacilli differ much in their size and 

 shape. This is especially true when the bacilli are grown in association 

 with other bacteria. The two bacilli of a pair may lie with their long 

 diameter in the same axis, or at an obtuse or an acute angle. The 

 bacilli possess no spores, but have in them highly refractile bodies, 

 some of which are the starting point for new bacilli. 



Staining. The Klebs-Loeffler bacilli stain readily with ordinary 

 aniline dyes, and retain fairly well their color after staining by Gram's 

 method. With Loeffler 's alkaline solution of methylene blue, and to a 

 less extent with other weak staining solutions, the bacilli from blood- 



