Sanitation, Discovery and Treatment of Carriers 407 



2. Finding the Colonies. — In most cases a limited variety of colonies appears. 

 It is best to look for those of meningococci with a hand lens along these lines last 

 traversed by the swab where they are most isolated and least numerous. Any 

 perfectly round colorless or creamy colony that is transparent and pearly by 

 transmitted light should be marked for further study. 



3. Transplanting the Colonies. — With a platum wire each marked colony is 

 touched. If it prove to be slightly viscid, it is transplanted to sheep-serum 

 dextrose agar-agar in tubes for further study, and placed in the incubator for 

 12-18 hours to grow. 



4. Identification of the Cultures. — When grown many of the cultures can be 

 rejected on the naked eye appearance as not meningococci. Suspicious growths 

 are next spread upon slides and stained by Gram's method. All not proving to 

 be Gia.m-negative diplococci are rejected. 



;. Final Identification of the Organism. — The few cultures remaining may be 

 meningococci or they may be other Gram-negative cocci — Micrococcus catarr- 

 halis, Micrococcus flavus. Micrococcus pharyngis siccus, etc. So it now becomes 

 necessary to apply the final test which is the application of the agglutinating 

 serum. For this purpose the investigator must be provided with the serum 



either making it himself or obtainig it from some laboratory where it is made, and 

 must be acquainted with its agglutinating value for previous titration with known 

 meningococci. 



One cubic centimeter of sterile physiological salt solution is placed in a small 

 test-tube. With a platinum loop a small quantity of the suspected culture is 

 picked up, and gently rubbed upon the inner wall of the test-tube just at the 

 level of the salt-solution until a uniform suspension of the micro-organism is 

 made. 



With a sterile pipette, the agglutinating serum is removed from the cautiously 

 opened container, and enough transferred either directly by measurement, or in- 

 directly after dilution, to each tube to give the appropriate dilution for effecting 

 the agglutination. One known culture of meningococcus similarly suspended in 

 salt solution, two tubes being prepared. One receives the agglutinating serum 

 and acts as the serum control, the other receives none and acts as the salt-solution 

 control. When all have received the necessary additions, they are stood in an 

 incubating oven and kept at a high temperature (SS°C.) for two hours, when the 

 results are read. 



The salt-solution meningococcus control tube should still contain a uniform 

 suspension; the serum meningococcus control tube and such of the others as are 

 •meningococci should show fine agglutinations like tiny snow flakes. These 

 copmonly sediment so that the tube should first be observed for its clarity and 

 then shaken to show the flocculi. Only the tubes showing fine agglutinations 

 should be regarded as meningococci. 



This method requires 48 hours for its completion and j-equires 

 two cultivations. As time is an important consideration, and^as 

 culture media are not always available in large quantities, a method 

 devised by Olitsky* may be used to advantage. The suspected 



* "Jour. Am. Med. Asso.," 1918, lxx. No. 8, p. 153- 



