496 PNEUMONIA. 



This is generally very observable at an early stage in all 

 difiuse inflammations of tlie true pulmonary structures ; in it 

 the lung-tissue becomes exceedingly vascular, of a darker 

 colour than natural, not uniform but mottled ; it is increased 

 in both absolute weight and specific gravity. Its tenacity is 

 lessened, the texture being more easily broken doAvn by pres- 

 sure than in health ; it is less crepitant or resilient, but is not 

 altogether void of air, as may bo discovered from the feeling 

 imparted on manipulation, and from the fact that it will still 

 float in water, and that when incised the fluid material con- 

 tained in the intimate tissue is of a frothy character. That it 

 contains as yet none of the true exudate of confirmed inflam- 

 mation is demonstrated by washing, which to a great extent 

 removes the exalted colouration. A section of pulmonary 

 tissue in this condition exhibits enlarged and engorged 

 capillary bloodvessels, dilated air-cells with varying conditions 

 of cell contents. This stage of engorgement may, in the living 

 animal, quietly subside, and the j)arts gradually resume their 

 normal condition, or it may develop into the more serious 

 lesion recognised as The stage of exudation, red hepatization, 

 or red softening. It must be recollected, however, that none 

 of the variations into which the morbid process of pulmonary 

 inflammation have been arbitrarily divided are sharply defined 

 or marked off, but that they imperce]3tibly shade into each 

 other. In this exudation stage Ave have, along with the 

 serum, i.an outpouring of the fibrinogenous materials of the 

 blood, the liquor sanguinis, and a migration of leucocytes and 

 some red globules into both the air-vesicles and interconnec- 

 tive lobular tissue ; the exuded fluid materials coagulate, and, 

 in so doing, enclose the various corpuscular elements. 



The physical appearances and characters of the lung-tissue m 

 this condition are somcAvhat difterent from the previous state of 

 engorgement. It is rarely so livid in colour, being reddish-broAvn 

 or dull red both on the outer surface and Avhen cut into ; its 

 specific gravity and absolute Aveight are increased ; there is little 

 or no air contained in the vesicles ; it does not crepitate on 

 manipulation ; it is extremely friable, the structure being easily 

 broken doAvn by the finger ; it does not collapse Avhen the chest 

 is laid open, cannot be injected or inflated, and is disposed to 

 sink in Avater. 



