i8o PRACTICAL BACTERIOLOGY. 



The appearance under the microscope of the 

 Streptococcus pyogenes is of a chain, of varying 

 length, consisting of globular cells arranged one after 

 another like a string of pearls. The majority of these 

 cells are only a little larger than those of the Staphy- 

 lococcus pyogenes, but very frequently threads occur, 

 in which a few single cells are distinctly larger than 

 the rest. These larger cells are, as a rule, separated 

 from one another by a number of smaller ones, which 

 gives the chain the appearance of a crown of roses, 

 although occasionally, however, two or three occur 

 together. It is extremely probable that these are per- 

 manent forms or Arthrospores. The following fact, 

 which may be observed in every very old culture, is 

 confirmatory to this theory. In such cultivations the 

 larger cells often are well stained, whilst the smaller 

 ones are paler, which appears to indicate that the 

 latter have commenced to degenerate, whilst the 

 former are still in possession of their full vitality. 

 The number of organisms which join together to 

 make a chain varies considerably. Generally there 

 are from five to ten members ; chains as long as those 

 portrayed in Fig. 3, Plate I., occur less frequently. 

 Often the chains ^re coiled up into tangled balls. 

 Sometimes, especially in liquid nutrient media, diplo- 

 cocci (two in a chain) occur. When division is about 

 to take place, the cells elongate themselves, becoming 

 constricted in their middles, whilst their ends remain 



