54 BACTERIOLOGICAL DIAGNOSIS. 
patient must be isolated and treated with antiseptic 
gargles. 
(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 communi- 
cate diphtheria to a susceptible subject. 
The significance of Hoffman’s bacillus is not yet 
settled. It is frequently found in the throat when the 
patient is convalescing from an attack of diphtheria, 
and sometimes in subjects 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 safest to regard any 
patient who presents these bacilli as being infectious. 
In other words, in the present state of our knowledge it 
is best not to draw any distinction between Hoffman’s 
bacillus and the true diphtheria bacillus, as far as infec- 
tivity is concerned. 
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. 
(0). 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 or ascitic agar. 
We again exclude errors arising in the laboratory. 
Whenever the culture tube remains sterile the exam- 
ination should be repeated. 
