METHODS OF DIAGNOSIS. 399 



Methods of Diagnosis. In the first place, the stools 

 ought to be examined microscopically. Dried film prepara- 

 tions should be made and stained by any ordinary stains, 

 though carbol-fuchsin diluted four times with water is 

 specially to be recommended. Hanging-drop preparations, 

 with or without the addition of a weak watery solution ot 

 gentian-violet or other stain, should also be made, by which 

 method the motility of the organism can be readily seen. 

 By microscopic examination the presence of spirilla will be 

 ascertained, and an idea as to their number obtained. In 

 some cases the cholera spirilla are so numerous in the 

 stools that a picture is presented which is obtained in no 

 other condition, and a microscopic examination may be 

 sufficient for practical purposes. According to Koch, a 

 diagnosis was made in 50 per cent of the cases during the 

 Hamburg epidemic by microscopic examination alone. 



If the organisms are very numerous, gelatine or agar 

 plates may be made at once and pure cultures obtained. 



If the spirilla occur in comparatively small numbers, the 

 best method is to inoculate peptone solution (l per cent) 

 and incubate for eight to twelve hours. At the end of that 

 time the spirilla will be found on microscopic examination 

 in enormous numbers at the surface, and thereafter plate 

 cultures can readily be made. If the spirilla are very few 

 in number, or if a suspected water is to be examined for 

 cholera organisms, the peptone solution which has been 

 inoculated should be examined at short intervals till the 

 spirilla are found microscopically. A second flask of peptone 

 solution should then be inoculated, and possibly again a 

 third from the second. By this method, properly carried 

 out, a culture may be obtained which, though impure, 

 contains a large proportion of the vibrios, and then plate 

 cultures may be made. 



When a spirillum has been obtained in pure condition 

 by these methods, the appearance of the colonies in plates 

 should be specially noted, the test for the cholera-red reaction 

 should be applied, and in many cases it is advisable to 

 test the effects of intraperitoneal injection of a portion of a 



