630 SPORADIC DISEASES. 



furnishing the exudative materials, which characterise the con- 

 dition of hepatization or consolidation that occurs in pneumonia. 



The various changes which occur in the course of pneumonia 

 are — Isf. Arterial injection, characterised by a brighter colour, 

 and dryness of the pulmonary tissue, a condition indicated by 

 harsh respiration and crepitating sounds. 2d. The arterial 

 injection is succeeded by a condition of engorgement, congestion 

 of the pulmonary vessels, and incipient oedema of the lung. The 

 substance of the lung is engorged with blood and bloody serum ; 

 externally it is of a dark red colour, and crepitates but slightly 

 under pressure ; it also pits under the finger, and is more easily 

 torn than healthy lung ; is heavier than natural, inelastic ; its 

 cells are filled with liquid, mixed with air. On being cut a 

 large quantity of bloody serosity escapes from the cut surface, 

 which is frothy in the earlier stages from admixture with air. 

 This, along with the commencing consolidation, proves that the 

 effusion lias been poured into the bronchial tubes and air vesicles 

 as well as into the pulmonary tissue. During this stage the 

 lung tissue will still float in water, although it is heavier and 

 less crepitant than natural. 



If a very thin section be made, and examined microscopically, 

 the capillaries will be found filled with blood ; the air vesicles 

 enlarged and granular, with incipient division of their nuclei ; 

 and exudation corpuscles, mingled with red globules, which have 

 escaped from the vessels and are seen in the alveoli. 



3d. lied Hepatization. — If the inflammation continue, other 

 changes occur in the lung substance. The lung is red externally 

 and internally ; is solid, sinks in water, and no longer crepitates 

 under pressure ; it, however, tears easily and breaks down under 

 pressure ; and on this account Andral objected to the term 

 hepatization, and termed the second stage of pneumonia red 

 softening — ramollissement rouge. The colour is less livid than 

 in the earher stage, being a dull reddish-brown, becoming 

 brighter on exposure to the air. This reddish-brown colour is 

 never very uniform, and in some animals diversity of colour 

 is very marked : thus in the ox the inflamed lungs present such 

 a variety of colour as to cause the term " marbled " to be 

 applied to it. This is due to the very distinctly lobulated 

 anatomical character of the ox's lungs, and the consecutive 

 nature of the lobar pneumonia. Dark red spots indicate the 



