216 BIOLOGY AND TECHNIQUE 



Throat Smears and Throat Examinations. The bacteriologist, if 

 possible, should take these specimens himself, or the physician tak- 

 ing them should take them only with a clear illumination of the 

 throat, taking his specimen from the exact spot where the lesion is 

 supposed to be located. 



For diphtheria examination, the specimen is taken with a 

 sterile swab, and plated directly upon Loeffler's medium. This 

 should be incubated without delay, and the swab sent to the labora- 

 tory with the culture. The method has been standardized and is 

 described in the section of diphtheria. 



For Vincent's angina examination, smears should be taken and 

 stained, best by strong gentian violet, such as used in the Gram 

 stain, and the smear searched for the characteristic spirilla, and 

 fusiform bacilli. If the patient is in the laboratory, it is best to 

 make a dark field examination. 



Examination of Lesions on the Genitalia. Lesions suspicious of 

 primary syphilitic nature should be gently washed, the superficial 

 pus removed, and only exudate from the bottom of the lesion taken. 

 If necessary, the lesion can be gently scraped and serum, mixed with 

 as little blood as possible, used. No examination for treponema 

 pallidum is equal to the dark field examination. It is important to 

 use only thick slides. A drop of the exudate is placed on the slide 

 and a cover-slip dropped on it. Then a drop of oil is placed on 

 the bottom of the slide, over the preparation and on the top of the 

 cover-slip, and the preparation is placed on the dark field condenser. 

 In doing this, care should be taken to avoid air bubbles in the oil. 



When suspicion of chancroid exists, the material should be in- 

 oculated immediately into tubes of coagulated and inactivated sterile 

 rabbit 's blood, and incubated according to the method of Teague. 



BACTERIA HABITUALLY INHABITING THE NORMAL HUMAN BODY 



In studying bacteria in disease, it is of considerable importance 

 to have a clear idea of the morphological and cultural characteristics 

 of forms which are frequently encountered in different parts of the 

 human body under normal conditions. 



Various cavities of the body which communicate with the ex- 

 ternal world, always contain considerable numbers of bacteria repre- 

 senting a large variety of species. Some of these may be habitual 

 saprophytes associated with that particular part of the body, others 



