LESS COMMON PYOGENIC ORGANISMS. 285 



the cultures after this time in the refrigerator, and 

 transplanting upon fresh gelatin every five or six days. 

 Marmorek^ finds the virulence preserved by growing 

 the organism in a mixture of 2 parts of horse or 

 human blood-serum and 1 part of nutrient bouillon, or 

 of 1 part of ascites-fluid and 2 parts of bouillon. 



Certain authors are of the opinion that a relation 

 exists between virulence and the length of the chains 

 formed by streptococci when growing in fluid media. 

 It is held that those forming the long chains, drcpto- 

 coceus hngus, are the only ones concerned in animal 

 pathology, and hence the only ones by which patho- 

 genic powers may be exhibited ; while those form- 

 ing the short chains, streptococcus brevis, are not, as a 

 rule, pathogenic, and may often be readily differentiated 

 from the other variety by more or less gross cultural 

 characteristics, such as slow liquefaction of gelatin, 

 visible growth on potato, etc.^ 



Antistreptococcus Serum. — For a time a great 

 deal of interest was created by the announcement of 

 Marmorek that he had succeeded in inducing in ani- 

 mals a state of immunity from streptococcus infection, 

 and that the blood-serum of such animals when injected 

 into other susceptible animals and human beings pos- 

 sessed not only the property of rendering them insus- 

 ceptible to this particular form of infection, but even 

 exhibited curative powers in cases already infected. 

 This serum was obtained from horses or asses that had 

 been rendered immune by the gradual introduction into 



'Marmorek: Annales de I'lustitut Pasteur, 1895. 



2 V. Lingelsheim : Zeitsehrift fur Hygiene, 1891, Band x., and 1892, 

 Band xii. Behring: Centralblatt fiir Bakteriologie und Parasiten- 

 kunde, 1892, Band xii. 



