48 CLINICAL BACTERIOLOGY AND H^MATOLOGY 



(c) That he is in danger of acquiring diphtheria if subjected 

 to any influence which lowers his vitality, or which would 

 cause ordinary sore throat in any ordinary person. 



(d) It always means that the person may communicate 

 diphtheria to a susceptible subject. 



The significance of Hoffmann's bacillus is not yet settled. 

 It is frequently found in the throat when the patient is con- 

 valescing from an attack of diphtheria, and sometimes in sub- 

 jects who afterwards develop diphtheria. It also appears to 

 cause epidemics of sore throat which do not present anything 

 remarkable in their clinical characters. It is not now usually 

 regarded as having any relation to the true diphtheria bacillus. 



A negative result may mean 



(a) That the patient is not suffering from diphtheria. 



(b) That the swab did not touch the affected area. 

 We exclude errors in technique and observation. 

 A sterile culture may mean 



(a) That an antiseptic was used too soon before taking the 

 swab. 



(b) That the diseased portion of the throat was not touched. 

 Other parts of the mouth contain numerous bacteria, but 

 many of them do not grow well on blood-serum. 



We again exclude errors arising" in the laboratory. 

 Whenever the culture-tube remains sterile; the examination 

 should be repeated. 



Prognosis. This cannot be made from the number of bacilli 

 present, but a study of the concomitant organisms may give 

 some help. The worst cases are associated with streptococci, 

 and if these organisms are present in large numbers the out- 

 look is comparatively grave. Staphylococci are of less evil 

 omen, and the other common organisms of the mouth unim- 

 portant. 



Further Details. The chief additional point concerns the question 

 of the " pseudo-diphtheria bacillus." This term is used in two ways 

 (i) as a synonym for the Hoffmann bacillus, described above, and (2) 

 to denote a bacillus identical in morphology, staining reactions, etc., 

 with that of diphtheria, but differing from it in being either quite 

 non-pathogenic, or in not causing the characteristic symptoms caused 

 by the true bacillus or its toxin. These organisms are very common, 

 being found on the skin, in the alimentary canal, in wounds, etc., 

 appearing, as a rule, to cause no harm. (One, the xerosis bacillus, is 

 dealt with subsequently.) Their differentiation from pathogenic 



