BACTERIOLOGICAL EXAMINATION OF MATERIAL 215 



contamination usually offers little difficulty. If the same micro- 

 organism appears in several of the plates and flasks, if colonies upon 

 the plates are well distributed within the center and under the 

 surface of the medium, and if the microorganisms themselves belong 

 to species which commonly cause septicemia, such as streptococcus 

 and pneumococcus, it is usually safe to assume that they emanated 

 from the patient's circulation. When colonies are present in one 

 plate or in one flask only, when they are situated only near the edges 

 of a plate or upon the surface of the medium, and when they belong 

 to varieties which are often found saprophytic upon skin or in air, 

 they must be looked upon with suspicion. It is a good rule to look 

 upon all staphylococcus albus cultures skeptically. 



Sputum. In examining sputum, sufficient emphasis cannot be 

 placed upon the necessity of collecting the sputum in a proper way. 

 The sputum collected by patients in the ordinary sputum cup con- 

 sists to a very large extent of material obtained from the mouth 

 and throat. If a successful examination of sputum is to be made, 

 the patient should be taught to rinse out his mouth thoroughly, and 

 the sputum collected directly after a cough. It is very little to 

 ask for this amount of care, if the examination is really worth mak- 

 ing at all. Sputum so collected should not be left in the ward, but 

 should be sent to the laboratory immediately. Smears should be 

 made on such sputum, with an intelligent idea of what is desired. 



For pneumococcus type examination, the sputum is thoroughly 

 washed and intraperitoneally injected into mice, according to the 

 detailed directions given for typing in the chapter on pneumococcus. 



For influenza bacillus examinations, thin smears of the sputum 

 should be stained by Gram and dilute carbol fuchsin. The char- 

 acteristic grouping of influenza bacilli is of considerable help. Plates 

 of chocolate agar are then streaked. 



Sputum for tuberculosis examination is thinly smeared and 

 stained by carbol fuchsin or Hermann's stain. When it is desired 

 to carry the examination beyond this in negative examinations, 

 washed sputum can be injected into guinea pigs, or the sputum can 

 be antiforminized, washed and then injected. Also, the anti- 

 forminized sediment can be examined by stain preparation. 



Direct culture of tubercle bacillus sputum can be made by treat- 

 ing with sodium hydrate and plating upon Petroff's gentian- violet- 

 egg medium, by the method described in detail in the section on 

 tuberculosis. 



