616 SPORADIC DISEASES. 



hours after the primary distension of the vessels, and consists in 

 the loosening and desquamation of the columnar epithelium at 

 the foci of greatest congestion. 



" The columnar epithelium is thus shed at a very early stage 

 of the attack, and takes no 'part whatever in tlie after changes 

 which ensue. It is never seen again until the other signs of 

 acute inflammation, such as the distension of the vessels, and 

 oedema of the basement membrane, have passed off. Subse- 

 quently we shall see that it is gradually reproduced. The 

 cause of this desquamation of the columnar epithelium seems to 

 be the oedema of the basement membrane loosening its under- 

 lying attachments, very much in the same way as the vesicles 

 which form in an acute inflammatory affection of the skin loosen 

 the attachments of the superficial layer of epidermis. The 

 removal of this protective covering from the mucous membrane 

 naturally leaves the latter in an exposed condition, and no 

 doubt the feeling of rawness experienced in acute catarrh of 

 the bronchi is due to the cold air acting upon an over-stimulated 

 and exposed mucous membrane. And, further, it can easily be 

 understood that, where this desquamation takes place to an 

 inordinately great extent, the loss of the ciliary action of the 

 columnar cells will seriously interfere with expectoration, and 

 tend to cause the catarrhal products to gravitate downwards 

 towards the smaller bronchi and air vesicles. This description 

 essentially coincides with what Socoloff found experimentally in 

 animals (Virchow's Archiv, vol. Ixviii, p. 611), in which he in- 

 duced an artificial bronchitis by the injection of irritants, such as 

 potassic bichromate, into the air passages. He states that one 

 of the first changes which ensued was the desquamation of the 

 columnar cells, and that they took no part in the catarrhal 

 inflammatory process." This early shedding of the columnar 

 cells, and their non-reproduction until after the subsidence of the 

 inflammatory process, is a fact of real importance, as it goes a long 

 way to explain the occurrence of those caseous tumours mis- 

 taken for tubercle, and so often confounded with that growth. 



The pneumonic process, which may supervene either by ex- 

 tension of the inflammatory process from the tubes to the alveoli, 

 or the irritation of inhaled inflammatory products subsequent to 

 collapse, is, in the earlier stage, commonly limited to scattered 

 groups of air vescicles, hence the term lobular which is applied 



