22 DAVID J. DAVIS 



are very numerous. But few polynuclear leucocytes are present, and 

 these are usually filled with the bacteria. If the exudate of an animal 

 inoculated with an amount insufficient to kill in 24 hours is examined 

 about the second or third day, a very different picture is presented. 

 The exudate is purulent and contains flakes of fibrin. The polynu- 

 clear leucocytes are very abundant, and are busily engaged ingesting 

 the bacteria. There are also present, in less numbers, large mononu- 

 clear cells. These cells often contain one or more polynuclear 

 leucocytes filled with bacilli. The ingested leucocytes may be seen 

 in various stages of intracellular digestion, some being nearly perfect, 

 while others show nothing but fragments of the nucleus. 



A number of animal experiments were made to determine the 

 effect of introducing another organism with the influenza-like bacilli 

 into the peritoneal cavity. This had been done with the influenza 

 bacillus and the streptococcus by Jacobson, who found that the 

 virulence of the bacilli could thus be increased so that much smaller 

 doses of the bacilli alone would be sufficient to kill. He obtained 

 both the bacilli and streptococci in the body fluids and heart's blood. 

 In my experiments a non-virulent Staphylococcus pyogenes aureus 

 was chiefly used. Two c.c. of a broth culture of this organism pro- 

 duced no effect when inoculated into the peritoneal cavity of guinea- 

 pigs. When J c.c. of this culture was inoculated with two blood- 

 agar slants of the pertussis organism, which, as above stated, rarely 

 killed, death invariably followed in 24 hours or less. From the 

 peritoneal exudate both organisms were isolated; from the heart's 

 blood, however, as a rule only the influenza-like bacilli were obtained, 

 and no staphylococci. In two animals, where large amounts of 

 staphylococci were injected, a few were obtained also in the heart's 

 blood. After passing the bacilli in symbiosis with staphylococci 

 through six animals, one blood- agar slant alone would kill an animal 

 in 24 hours, i. e., its virulence had been more than doubled. The 

 effect of M catarrhalis and an avirulent streptococcus upon the 

 influenza-like bacilli was found to be very similar to that of 

 Staphylococcus, i. e., the bacilli were distinctly more virulent when 

 associated with these organisms than when inoculated alone. In all 

 these experiments controls were made by inoculating animals with 

 the same or larger amounts of the organisms separately. 



