396 PATHOGENIC MICROORGANISMS 



Staphylococci, besides the toxic substances already mentioned, 

 give rise to gelatinase, spoken of in the section upon cultivation, 

 and to a proteolytic ferment by means of which albuminous media 

 (Loeffler's serum) may be slightly digested. 



Immunization. Animals can be rendered actively immuix by 

 repeated inoculations with carefully graded doses of living or d< -ad 

 staphylococcus cultures. 35 The production of antistaphylolysin and 

 of antileucocidin in the sera of animals so treated, has b< < -n allud< <[ 

 to in the preceding sections. The sera of such actively immuni/' <1 

 animals possess distinct protective power when adminisi< n-4 to 

 other animals, slightly before or at the same time with an inoculation 

 of staphylococci. They do not, however, exhibit very high bacU-ri- 

 cidal power in vitro, the protective properties depending probably 

 upon their opsonic contents. 36 



Agglutinins have been demonstrated in staphylococcus immune 

 sera by a number of authors, and have been of some slight valu< in 

 differentiating between the several groups of staphylococc-i. 7 A 

 rather surprising result of these researches has been the recognition 

 that immune sera obtained with pathogenic staphylococci will ag- 

 glutinate other pathogenic staphylococci, whether belonging to tin- 

 group of Staphylococcus pyogenes aureus or that of Staphylocoocus 

 pyogenes albus, but will not agglutinate any of the non-pathogenic 

 members of either group. 38 In view of the recent studios on the 

 antigenic classification of streptococci and pneumococci, a re- 

 examination of these relationships within the staphylococcus group 

 should be undertaken. It is more than likely that this group is a 

 heterogeneous one, and that, for purposes of intelligent expM -irm -nta- 

 tion in serum and vaccine therapy, an antigenic classification should 

 be attempted. 



Active immunization of human beings suffering from staphylo- 

 coccus infections has been extensively practiced by Wright, in con- 

 nection with his work on opsonins. There can be no question about 

 the fact that the opsonic substances in the blood are increased by 

 the injection of dead staphylococci. The procedure is of therapeutic 

 value in subacute and chronic cases. The work of Hiss on the use 



*Bichet et Hericourt, Compt. rend, de 1'acad. des sci., cvii, 1888. 

 *Kolle und Otto, Zeit. f. Hyg., xli, 1902. 



" Proscher, Cent. f. Bakt., xxxiv, 1903; v. Lingelsheim, "AetioL u. Therap. d. 

 Staphyl.," etc., Wien, 1900. 



"Proscher, Deut. med. Woch., xi, 1903. 



