BACTERIOLOGY 441 



as far as given refers more particularly to the acute form of the 

 disease. 



In the more chronic form there is considerable fibrosis of the 

 affected lung, i. e., new formation of inflammatory connective tissue. 

 Areas in the lung appearing almost as solid as meat (a condition 

 known as carnificatiori) alternate with necrotic and occasionally 

 calcified areas. The necrotic portions, or sequesters, may assume a 

 considerable size and may bulge as nodular masses above the general 

 pleural surface. The sequesters are frequently surrounded by a 

 tough, fibrous, connective tissue capsule and discharge, after an 

 incision through the latter, a mushy, dirty mass and more solid 

 particles. Sometimes such softened, necrotic portions of the lung 

 break into a bronchus and are discharged through it into the outside 

 world. They vary in size from a walnut to a child's head, and they 

 may be formed after a preliminary purulent infiltration, or the serous 

 yellowish exudate may so compress bloodvessels and lymphatics 

 that portions of the lung are deprived of their nutrition and necrosis 

 results from the lack of blood supply. 



Histologic studies by Pourcelot and MacFadyean have shown that 

 the first tissue changes occur in the interalveolar septa and that their 

 lymphatics become distended with a finely granular fibrinous coagulum 

 containing a few cells. The alveoli at this early stage show no 

 marked changes, a little later, however, the zone adjacent to the 

 alveolar wall secretes a fibrinous exudate which extends toward the 

 centre. At the same time the interalveolar connective tissue becomes 

 infiltrated with leukocytes and subsequently thickened by newly 

 formed connective tissue. The mucosa becomes covered with a 

 fibrinous exudate. The changes in the pleura first consist in an 

 edematous infiltration, later the surface becomes covered with a 

 fibrinous exudate, false membranes are formed, and these finally 

 become organized and replaced by cicatricial connective tissue. 

 The pericardium is sometimes involved and the peritoneal cavity 

 occasionally contains some fluid and an exudate upon its surface. 



Bacteriology. Nocard describes the bacteriology of the disease as 

 follows: The examination of stained specimens from the virulent 

 serous exudate infiltrating the alveoli does not show any bacteria. This 

 serous fluid, however, when properly preserved or mixed with bouillon, 

 does not lose its virulency. In spite of the fact that it apparently 

 contains no microorganisms, its inoculation into a place as unfavorable 

 as the end of the tail of a cow produces considerable reaction and 

 sometimes death. If heated to from 65 to 70 C. the exudate loses 

 its virulency. This also occurs after certain processes of filtration. 

 If collodion sacs, inoculated with a trace of the exudate obtained 

 under aseptic precautions, are implanted into the peritoneal cavities 

 of rabbits and re-obtained after fifteen to twenty days, the contents 

 of the sacs have become opalescent and slightly cloudy. Upon 

 microscopic examination of the contents neither cells nor bacteria 



