242 BACILLUS DIPHTHERIA. 



The membrane represents the local reaction, and the constitu- 

 tional symptoms are due to absorption of the toxin. When 

 the germ lodges on the mucous membrane, it excites intense 

 congestion and inflammation in the upper layers. This is 

 followed by exudation of serum into these layers and a conse- 

 quent lessened nutrition to the tissues. This lack of nutrition, 

 together with the toxin elaborated by the germ, is responsible 

 for the coagulation-necrosis which follows, and represents the 

 final step in the process. This necrosed tissue is the so-called 

 pseudomembrane of diphtheria. There is no deposit on the 

 mucosa. It is a death of its superficial layers. The bacilli 

 are found in greatest number in the older portions of the 

 membrane. From the original site of infection the mem- 

 brane gradually spreads to other parts of the throat, nares, 

 and larynx. The appearance of this membrane is not a 

 criterion of the toxicity or virulence of the bacilli. 



The toxin elaborated in this membrane is absorbed by the 

 bloodvessels and lymphatics, and distributed throughout the 

 body. Its entrance into the circulation is marked by the 

 appearance of constitutional symptoms. The bacilli are rarely, 

 if ever, found in the blood. 



Diphtheria is seldom a pure infection. Associated with 

 the diphtheria bacillus we find the staphylococcus, strepto- 

 coccus, pneumococcus, and occasionally Bacillus coli com- 

 munis. These associated organisms play a very important 

 role in diphtheria. They are largely responsible for the com- 

 plications of diphtheria, except the paralyses which are due to 

 the toxin, and for those severe, aggravated cases which resist 

 all treatment. The streptococcus is most to be feared, because, 

 as has been demonstrated experimentally, when the diphtheria 

 bacillus and the streptococcus are associated the latter increases 

 the virulence of the former. 



Infection : The disease is always conveyed from one per- 

 son to another either directly or indirectly. Kissing a con- 

 valescent is a common source of infection. The bacillus 

 has been found in the throat for as long a period as six 

 months after subsidence of the disease. Persons who have 

 come in contact with the disease may not themselves be- 

 come infected, but may convey the disease to others. The 



