STREPTOCOCCI. 43 



prominent ear veins. If the needle of the syringe is not inserted in the 

 vein it will be difficult to force in the material and a swelling will im- 

 mediately show itself. 



Besides the morphological and pathogenic variations, Schottmuller 

 has noted differences where these organisms are grown on one part of 

 blood and three parts of agar. On this medium Strep, erysipelatis has 

 a hemolytic action, the laking of the red cells bringing about a more or 

 less clear ring surrounding the colony. The short- chain streptococci 

 do not have a hemolytic halo. 



Some of the English authorities have introduced biochemical 

 methods of differentiating: the Strep, pyogenes coagulating milk, 

 reducing neutral red, and producing acid in lactose, saccharose, 

 mannite or inulin media. When we consider the biochemical varia- 

 tions which a single organism, as the colon bacillus, may exhibit, the 

 value of such methods of differentiating may well be questioned. The 

 question of the symbiotic relationship, which, when established between 

 two or more bacteria, may cause harmless organisms to take on viru- 

 lence, would appear to be a more important consideration. 



Almost without exception, streptococci are .Gram positive. Their 

 colonies are quite small, but distinct and discrete. In appearance the 

 colonies of streptococci and pneumococci are practically identical. In a 

 blood- serum throat culture pneumococcus and streptococcus colonies 

 are the smallest, diphtheria ones are quite small and discrete, but slightly 

 flatter. (Always examine the water of condensation for streptococci.) 

 The sarcina and staphylococcus colonies are much larger. 



Streptococci are commonly the cause of diffuse phlegmonous in- 

 flammation, while the staphylococci cause circumscribed lesions. 

 Streptococci cause necrosis and do not characteristically produce pus. 

 The importance of the streptococcus as a secondary infection in diph- 

 theria, tuberculosis, small-pox and even in typhoid fever must always 

 be kept in mind. It is this infection which does not respond to diph- 

 theria antitoxin, and not the diphtheria one. 



SARCINA FORMS. 



These are best observed in hanging-drop preparations, when they 

 can be seen as little cubes, like a parcel tied with a string, and by noting 



