234 BACTERIOLOGICAL EXAMINATION OF MATERIAL 



For a majority of bacteria, freshly prepared blood agar plates are the 

 most satisfactory media to employ. 1 Hemolytic streptococci, pneumo- 

 cocci, Pneumococcus mucosus and influenza bacilli grow upon this 

 medium. 



Diphtheria bacilli are grown upon Loffler's blood serum, as described 

 in the section on diphtheria. 



Tubercle bacilli can be readily distinguished from lepra bacilli, 

 nasal secretion bacilli and adventitious acid-fast organisms by the 

 injection of washed, cheesy particles from sputum into guinea-pigs. 



The organism commonly found in Vincent's angina (Bacillus fusi- 

 formis) is not readily cultivated upon ordinary media. Its recognition 

 usually depends upon its demonstration in smears prepared directly 

 from the lesions. 



Bacteriological Examination of the Eye. The normal conjunctival 

 sac frequently contains Staphylococcus albus and Bacillus xerosis; 

 indeed these organisms are so commonly found in this region that they 

 are regarded as normal inhabitants. Abnormally a variety of bacteria 

 may develop on the conjunctiva, frequently causing a violent inflam- 

 mation. Material for bacteriological examination is best obtained 

 after gently flooding the conjunctival sac with a few drops of sterile 

 salt solution, which are removed with a sterile cotton swab. Then a 

 small sterile cotton swab is gently rubbed over the conjunctival sur- 

 face and inoculated into suitable media after a Gram-stained smear 

 has been examined. 



The gonococcus, Koch- Weeks bacillus, and the pneumococcus are 

 more commonly the incitants of acute inflammation of the conjunctiva; 

 less frequently hemoglobinophilic bacilli (B. influenzse particularly) 

 or Bacillus pyocyaneus may be found. An examination of Gram- 

 stained smears will indicate the media to be employed if isolation of 

 the organisms in pure culture is desired. The meningococcus is occa- 

 sionally found in conjunctival inflammations in cases of cerebrospinal 

 meningitis; it must not be confused with the gonococcus. Micrococcus 

 catarrhalis, which resembles both the gonococcus and meningococcus 

 in its morphology and staining reactions, does not produce an acute 

 conjunctival inflammation with a profuse purulent discharge rather, 

 this organism usually gives rise to a slight reaction, even though the 



1 Several drops of sterile blood, obtained from the finger or the lobe of the ear after 

 a preliminary sterilization, are placed in the centre of an agar plate. The material to 

 be studied is streaked out radially from the blood. Enough blood can be moved with 

 the organisms by this method to insure growth. 



