124 SUPPOSED INSTANCES [CH. ix 



(4) The injection of organisms into the peritoneal cavity 

 would have a threefold effect, it would make the animal ill, 

 produce a more or less marked peritonitis, and finally kill 

 the animal. All three events would favour the invasion of 

 the peritoneal cavity by organisms. If the vitality of the 

 body and consequently of the peritoneum is lowered, organisms 

 can penetrate it from the gut even in the absence of any 

 definite lesion or inflammation. Ford (1900) noted that in 

 animals whose vitality was lowered, by fasting or unhealthy 

 conditions, bacteria were more abundant in the internal 

 organs, and that this applied particularly to bacteria of the 

 colon type. Dudgeon and Sargent (1907) have shown that at 

 the earliest stage of peritonitis the staphylococcus albus 

 (either normally present on the surface of the gut or pene- 

 trating from within it) increases with enormous rapidity. 

 Miiller (1910) remarks that when organisms (e.g. typhoid 

 bacilli) are injected into the peritoneal cavity they at first 

 decrease in number owing to the bactericidal effect of the 

 body fluids but later on increase again. It is during this 

 early stage when the injected organisms are decreasing rapidly 

 that the staphylococcus albus (and possibly, in animals, the 

 bacteria present in the internal organs) are increasing rapidly. 

 A culture removed during this period might well convey the 

 impression that a mutation had occurred. 



Dudgeon and Sargent (1907) mention that the staphylo- 

 coccus albus is often quite non-pathogenic in the peritoneal 

 cavity of the guineapig. 



After death there is a rapid invasion of the peritoneal 

 cavity by organisms, particularly by B. coli from the gut, so 

 that the true nature of the infection becomes obscured. In 

 illustration of this point, Dudgeon and Sargent (1907) record 

 a case of pneumococcal peritonitis in which the peritoneal 

 exudate one hour after death gave a pure culture of pneumo- 

 cocci, whereas 26 hours later B. coli alone could be recognised 

 in the same exudate. 



It is not possible, therefore, to exclude in Major Horrocks's 

 experiments the possibility of an invasion of the peritoneal 

 cavity from the gut, following either the inoculation or the 

 death of the animal. 



