280 BACTERIOLOGY. 



which serve to protect rabbits from twice the fatal dose 

 of a staphylococcus culture. Similarly the serum of 

 immunized rabbits and goats, as shown by the exper- 

 iments of Petersen, possesses about the same degree of 

 protective powers. No antitoxic power could be dem- 

 onstrated in the serum of the treated animals. The 

 extremely limited degree of the protective power of the 

 antistaphylococcus serums prepared thus far makes it 

 impossible to employ them for curative purposes in 

 human beings, as Petersen calculated that an adult 

 would require from 350 to 700 c.c. of the serum at a sin- 

 gle dose, as judged by its effects on the lower animals. 



OTHER COMMON PYOGENIC ORGANISMS. 



MICROCOCCUS PYOGENES (Rosenbach), Migula, 1900. Synonyms: 

 Staphylococcus pyogenes albus, Rosenbach, 1884 ; Micrococcus pyogenes 

 albus, Lehmann and Neumann, 1896. 



MICROCOCCUS CITREUS (Passet), Migula, 1900. Synonym: Staphylo- 

 coccus pyogenes citreus, Passet, 1885. 



The pus of an acute abscess in the human being 

 may sometimes contain organisms other than micro- 

 coccus aureus. Micrococcus pyogenes and citreus may be 

 found. The colonies of the former are white, those of 

 the latter are lemon color. With these exceptions they 

 are in all essential cultural peculiarities similar to micro- 

 coccus aureus. As a rule, they are not virulent for 

 animals, and when they do possess pathogenic proper- 

 ties, it is in a much lower degree than is commonly the 

 case with the golden staphylococcus. Streptococcus 

 pyogenes is also sometimes present. The commonest 

 of the pyogenic organisms, however, is that just de- 

 scribed, viz., micrococcus aureus. An organism that is 

 almost universally present in the skin, and is often con- 

 cerned in producing mild forms of inflammation, is 



