DIPHTHERIA 47 



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 convalescing 

 from an attack of diphtheria, and sometimes in subjects who after- 

 wards 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. 



(J) 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 examination 

 should be repeated. 



TETANUS 



The pathology of tetanus is very much like that of diphtheria. 

 In each disease the specific bacilli are localized at or near the 

 region at which they enter the body, and form a toxin which 

 affects distant organs. In the case of diphtheria, as we have seen, 

 the toxin passes by the blood-stream, but in tetanus it creeps from 

 the region where it is produced up the peripheral nerves to the 

 brain and spinal cord. In each case research has shown that an 

 antitoxin is formed which neutralizes this toxin and prevents it 

 from uniting with the cells of the body, but which has not the 

 power of turning it out from such a combination. In other words, 

 tetanus antitoxin, like that of diphtheria, is preventive, but not 

 curative. But here, unfortunately, the resemblance between the 

 two diseases ceases. The local lesion in diphtheria is obvious, 

 and its presence causes a good deal of inconvenience to the patient ; 



