460 CHOLERA 



dition, 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. In the case of the first appear- 

 ance of a cholera- like disease, however, all the other tests 

 should be applied before a definite diagnosis of cholera is made. 

 Dunbar has recently introduced a method for rapid diagnosis 

 which depends on the properties of an anti-cholera serum. Two 

 hanging-drop preparations are made, each consisting of a small 

 portion of mucus from the suspected stool broken up in peptone 

 solution. To one a drop of a 50-fold dilution of normal serum 

 is added, to the other a drop of a 500-fold dilution of an active 

 cholera serum. If the spirilla present are cholera organisms, 

 they retain their motility in the first preparation, while they lose 

 it and then become agglutinated in the second. By this method 

 a diagnosis may sometimes be given in a few minutes. 



If the organisms are very numerous, gelatin 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 (1 per cent.) and incubate 

 for from 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, and then plates may be made. In such 

 circumstances Dieudonne's medium (p. 44) has been found of 

 much service. 



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 recent agar culture 

 in a guinea-pig, the amount sufficient to cause death being also 

 ascertained. The agglutinating or sedimenting properties of the 

 serum of the patient should be tested against a known cholera 

 organism, and against the spirillum cultivated from the case. 

 The action of an anti-cholera serum, i.e. the serum of an animal 

 immunised against the cholera spirillum, should be tested in a 

 similar manner. 



Up till recent times there had been cultivated, from sources 



