350 MEDICAL BACTERIOLOGY 



6. Make a set of ordinary agar plates, or streak cultures, and 

 keep at 38 C. 



The gonococcus grows on the first two media, but not on the plain 

 agar. The gonococeus is the only organism that : 



1. Occurs in groups (cell-colonies) in pus-cells. 



2. Is decolorized by Gram's method. 



3. Does not grow on agar at room or blood heat. 

 Micrococcus Weichselbaumii (M. intracellularis). 



Pus may be obtained by lumbar puncture which is performed as 

 follows : The back of the patient and the operator 's hands should 

 be made sterile. The needle (4 cm. X 1 mm. for children) should 

 be boiled 10 minutes. The patient should lie on the right side, with 

 the knees drawn up and the uppermost shoulder so depressed as to 

 present the spinal column to the operator. The puncture is gen- 

 erally made between the third and fourth lumbar vertebrae. The 

 thumb of the left hand is pressed between the spinous processes, and 

 the point of the needle is entered about 1 cm. to the right of the 

 median line, and on a level with the thumb nail, and directed slightly 

 upwards and inward, toward the median line. At a depth of 3 or 

 4 cm. in children and 7 or 8 in adults the needle enters the subarach- 

 noid space and the fluid flows usually by drops. This is allowed to 

 drop into an absolutely clean test-tube, which has previously been 

 plugged and sterilized. From 5 to 15 cc. of the fluid is a sufficient 

 quantity for examination. Cultures should be made at once on 

 blood agar and on plain agar (M. & W. 371). After standing some 

 hours, the sediment should be examined in cover-glass preparations, 

 stained with Loeffler's methylen blue and by Gram's method. 



Microccus Weichselbaumii stains by Loeffler's method and ap- 

 pears as a diplococcus in groups in the pus cells, is decolorized by 

 Gram's method, and grows on blood-agar, and feebly on ordinary 

 agar at 38 C. 



The following organisms are also found occasionally. For meth- 

 ods of diagnosis see exercises indicated. 



Bacillus coli. 103. 



Bacterium tuberculosis. 101. 



Bacterium leprae. For method of staining, see 99. 



Bacterium pneumoniae. Stain for capsule. Cultivate on blood- 

 agar. 101. 



Bacterium mallei. 



a. Widal reaction. (If in man, typhoid and diphtheria must be 

 excluded in case of a positive reaction.) 



