DIPHTHEEIA. 47 



Skin is an effectual barrier to diphtheritic infection, but 

 wounds or raw surfaces may be attacked. 



When diphtheria attacks tissues which are naturally lax, con- 

 siderable oedema may accompany the formation of false membrane. 

 (Edematous swelling may therefore occur in the fauces, soft 

 palate, uvula, and superior opening of larynx. Occasionally 

 destructive ulceration of the same parts is met with. 



Diphtheria may prove dangerous either from the mechanical 

 suffocative effects, which depend upon the localisation of the 

 membranous exudation, or from toxaemia, which is dependent 

 upon absorption. 



Suffocative symptoms are produced when the larynx, trachea, 

 bronchi or bronchioles are involved. Of these the larynx is the 

 first affected by virtue of its position, and its involvement 

 produces urgent symptoms on account of the ease with which 

 the upper laryngeal aperture is occluded by membrane and 

 oedema. Even after tracheotomy it is often possible to observe 

 the deadly effect of occlusion of the lower air passages. 



Toxic symptoms in diphtheria are determined by two factors : 

 first, the extent of the membranous exudation, and, secondly, 

 the facility with which absorption can take place. The 

 comparative harmlessness of membrane limited to the nasal 

 cavities may possibly be due to lack of facilities for absorption. 

 There are abundant indications that free absorption takes place 

 in the regions of the nasopharynx and fauces. 



The arrangement of the lymphatics of the air tubes renders it 

 probable that but little lymphatic absorption takes place in the 

 trachea and bronchi, where the basement membrane completely 

 cuts off the deep lymphatics from the surface lining of the tubes. 



The local lymphatic glandular swelling in diphtheria has 

 already been alluded to ; the inflammation when it spreads 

 outside the glandular capsules may give rise to a brawny infiltra- 

 tion of the connective tissues of the neck. It is stated that the 

 parotid and submandibular salivary glands may become inflamed 

 in diphtheria ; when this really occurs it is presumably due to 

 an extension of infection from the mouth along the ducts of the 



