Pathogenesis. Anatomical Clianges. 35 



membrane affords an effectual protection. Feeding and in- 

 halation have failed to successfully transmit the infection to 

 experiment animals. 



Pathogenesis. After the germination of the spores in the 

 h^npll spaces the bacilli continue to multiply by fission at the 

 point of infection until large bacterial colonies develop'. In the 

 meantime gases are formed by the dissociation of the tissue 

 fluids, and toxins are produced under the influence of which the 

 blood vessels are dilated, allowing the blood plasma to transude 

 into the connective tissue spaces through the relaxed walls of the 

 vessels. With the penetration of the bacilli the swelling en- 

 larges, and in case the point of infection is near the abdominal 

 cavity, the bacilli multiply rapidly on the surface of the 

 peritoneum where they grow into long threads. At the same 

 time the absorbed toxins act also on the central nervous system, 

 particularly on the respiratory and heat centers, as a result of 

 which respiration becomes difficult and the temperature elevated. 



The edema bacilli are capable of multiplying in the tissues 

 only under special conditions. The spores will germinate only 

 in the presence of toxins (from older cultures) in the tissues, 

 because otherwise they would soon be taken up by the phago- 

 cytes and rendered harmless. Their propagation is also facili- 

 tated by the simultaneous entrance into the tissues of other 

 micro-organisms (Bac. prodigiosus, staphlycocci, diplococcus 

 pyogenes and others). In addition propagation is aided by 

 the presence of particles of dirt or sand which protect the 

 spores mechanically against 'the phagocytes, while toxins and 

 substances like lactic acid, keep away the cells through negative 

 chemotaxis (Besson, Leclainche & Vallee). At the same time 

 the presence of other bacteria has an influence on the develop- 

 ment of the pathological changes and gives rise to numerous 

 cases of mixed infection. 



Anatomical changes. During the formation of a swelling 

 in any part of the body the connective tissue becomes distended 

 and inliltrated with a yellow or reddish fluid which contains 

 gas bubbles and liberates a peculiar disagreeable odor. The 

 gelatinous infiltration of the connective tissue may also extend 

 between the deeper layers of the muscles, while the muscle 

 substance proper turns pale yellow or dark red in color, be- 

 comes brittle and tears readily. The connective tissue appears 

 in places permeated with smaller or larger hemorrhages. The 

 abdominal cavity contains a small quantity of reddish serous 

 fluid ; the peritoneum is markedly injected, lustreless, but is not 

 covered with an exudate. 



If the malignant edema has developed after parturition, the 

 uterus is found insufficiently contracted, and the subserous con- 

 nective tissue of the small pelvis shows edematous infiltration. 

 The wall of the uterus is also edematous, the mucous membrane 



