DIPHTHERIA. 43 
PART II. 
DIAGNOSIS OF CERTAIN DISEASES. 
DIPHTHERIA. 
Diphtheria is a local disease with general symptoms. 
The local symptoms are due to the local action of the 
bacillus which causes the disease, while the general 
symptoms are due to the toxin or poison which they 
produce and which is carried in the blood-stream to the 
brain, heart and other organs. Now the local symptoms 
are comparatively unimportant, and it is to the general 
symptoms caused by the toxin that diphtheria owes the 
greater part of its high mortality. Diphtheria antitoxin 
neutralises this toxin (much in the same way as an 
alkali neutralises an acid) and prevents it from harming 
the vital structures; but it does ot repair the harm 
that the toxin has done. It is obvious, therefore, that 
we must not make our diagnosis of diphtheria from the 
general symptoms if the antitoxin treatment is to do 
any good. The diagnosis is to be made from the local 
symptoms, and this is what we can rarely do by ordin- 
ary clinical methods at a stage sufficiently early to get 
the full value of the antitoxin treatment. 
The practitioner has a choice of two methods. He 
may inject all patients who suffer from sore throats 
which present the slightest resemblance to those seen in 
diphtheria, or he may employ bacteriological methods 
