UDDER-STREPTOMYCOSIS 39 



the appearance of the pathogenic streptococcus changes 

 considerably under different conditions and therefore pre- 

 sents less effective type characteristics. Special diagnostic 

 type characteristics are not known. For a practical bac- 

 teriological classification of the pathogenic streptococci we 

 must wait for further work to be done. [Blake, The Classi- 

 fication of Streptococci, Journal of Medical Research, 

 March, 1917.] 



Occurrence. — The pathogenic streptococcus is not 

 confined to any special geographical district but appears 

 to be somewhat uniformly distributed. In Sweden it occurs 

 throughout the entire country. Its occurrence is general. 

 The frequency of the infection, especially the wound-infec- 

 tion, indicates that it often occurs in the dust, in the soil 

 of the cow stalls, and in the excrement. 



Morphology. — The pathogenic streptococcus presents 

 variations in size. The greatest diameter can vary from 

 0.9 to 2.3 micra. These are dwarf to giant forms. Usually, 

 however, the greatest diameter is about 1 micron. 



The form as a rule is Qgg- or lancet-shaped, seldom 

 regularly round like a ball. Frequently the egg forms are 

 so affected that they resemble rod-shaped organisms. 



As above stated, the individuals form chains. The num- 

 ber of individuals in each chain is variable. In animal 

 bodies the chains are as a rule short, usually only two indi- 

 viduals (diplococci) or from three to five individuals. In 

 body fluids, as milk or pleuritic exudate, however, the chains 

 may reach a considerable length, 100 individuals or more. 

 Upon cultivation, especially in fluid culture media, as 

 bouillon, the chains are usually very long. With the diplo- 

 cocci and the short chains the individuals are arranged 

 longitudinally like eggs with the points against each other. 

 In the longer chains the individuals are usually arranged 

 transversely as eggs with their long sides against each other. 

 The explanation of this condition is that in the latter case 



