BACTERIA IN DIPHTHERIA. 457 



not simply encounter bacilli which are very virulent and bacilli which are 

 non- virulent; between these two extremes there are bacilli of every degree 

 of virulence." 



Abbott, in 1891, published the result of his researches with 

 reference to the presence of the pseudo-diphtheritic bacillus in 

 benign throat affections. He made a bacteriological study of fifty- 

 three patients, nine of whom were suffering from acute phaiyngitis, 

 fourteen from acute follicular tonsillitis, eight from ordinary post- 

 nasal catarrh, two from simple enlarged tonsils, fifteen from chronic 

 pharyngitis, one from subacute laryngitis, one from chronic laryngi- 

 tis, one from rhinitis, and two from an affection of the tonsils and 

 pharynx. In forty-nine cases nothing of particular interest was ob- 

 served. A variety of microorganisms were isolated, and of these 

 the pyogenic micrococci were the most common. 



In four cases microorganisms were found which resembled the 

 Bacillus diphtheria of Loffler in their morphology and growth in cul- 

 ture media, but which proved not to be pathogenic. Abbott says : 

 " The single point of distinction that can be made out between the 

 organisms obtained from Cases L, III., and IV. and the true bacil- 

 lus of diphtheria is in the absence of pathogenic properties from the 

 former, whereas in addition to this point of distinction the organism 

 from Case II. gives, as has been stated, a decided and distinct 

 growth upon the surface of sterilized potato. " 



Recent authors are generally inclined to the opinion that bacilli 

 which resemble the diphtheria bacilli in every respect except that 

 they are non-pathogenic should be regarded as attenuated varieties 

 of the diphtheria bacillus rather than as belonging to a distinct 

 species the so-called "pseudo-diphtheria" bacillus. However, there 

 are bacilli which closely resemble the bacillus of diphtheria and yei 

 may be differentiated from it otherwise than by the test upon sus- 

 ceptible animals. Neisser has given us a staining method which is 

 especially useful in making this differential diagnosis. The culture 

 of the bacillus to be tested is grown upon Loifler's blood-serum mix- 

 ture. This is solidified at a temperature of 100 C., and grown in 

 an incubator at a temperature between 34 and 36 C. The staining 

 of a cover-glass preparation from such a culture is effected by the 

 following method : Methylene blue, one gramme; alcohol (96), two 

 cubic centimetres ; dissolve and add distilled water, nine hundred and 

 fifty cubic centimetres, and acetic acid, fifty cubic centimetres. From 

 one to three seconds only will be required to stain the cover-glass 

 preparation with this solution; it should then be carefully washed in 

 water and stained in a solution made by adding two grammes of 

 vesuvin to one litre of boiling water. This solution is allowed to 

 cool before using, and from three to five seconds will be sufficient 



