348 BACTERIA PATHOGENIC TO MAN 



In septicaemia the culture method is always required to demonstrate 

 the presence of streptococci, as the microscopic examination of speci- 

 mens of blood is not sufficient. For this purpose from 10 to 15 c.c. of 

 the blood should be drawn from the vein of the arm aseptically by 

 means of a hypodermic needle, and to each of three tubes containing 

 10 c.c. of melted nutrient agar kept at about 43 C. 1 c.c. of blood is 

 added. After thoroughly mixing the contents are poured into Petri 

 dishes. The remainder is added to flasks or tubes of nutrient broth,, 

 in order to produce an adequate development of the cocci, which are 

 found in small numbers in the bloodvessels. Petruschky is of the 

 opinion that the cocci can best be shown in blood by animal inocu- 

 lation. Having withdrawn from the patient 10 c.c. of blood by means 

 of a hypodermic syringe, under aseptic precautions, he injects a por- 

 tion of this into the abdominal cavity of a mouse, while the other por- 

 tion is planted in bouillon. Mice thus inoculated die from septicaemia 

 when virulent streptococci are present only in very small numbers in 

 the blood. If a successful inoculation takes place we can, through the 

 absence or presence of the development of capsules, often differentiate 

 between the pneumococcus and the streptococcus, which cultures may 

 fail to do. The development of a wide, clear zone about the colonies,, 

 without a development of green pigment, indicates that the streptococci 

 belong to the pyogenes type. The absence of a definite zone and the 

 development of a green color indicates that they are pneumococci or 

 streptococci which in these two respects resemble pneumococci. The 

 growth in the Hiss inulin serum medium will generally differentiate 

 between the two, as the pneumococci usually coagulate the serum, 

 while the great majority of streptococci do not., The morphological 

 and cultural characteristics of the streptococcus give us, unfortunately r 

 no absolute knowledge as to the influence which the protecting serum 

 will have. The actual test is here our only method. The detection of 

 the streptococcus in the blood is in itself an unfavorable prognostic 

 sign. 



The blood cultures in many cases of septicaemia give no positive 

 results, for many of these cases develop their symptoms and even die 

 from the absorption of toxins from the local infection, such as an ampu- 

 tation wound or an infected uterus or peritoneum, and the bacteria 

 never invade the blood. When we get negative results we are, as a rule, 

 utterly unable to test the case with curative serums with any accuracy, 

 for the sepsis may be due to either the streptococcus, colon bacillus, 

 staphylococcus, or a number of other pathogenic varieties of bacteria. 



