Isolation of Specific Pathogenes. 73 



placed in long, narrow test tubes. To each of these tubes 

 enough typhoid serum of known potency was added to 

 make a regularly graded series, 1-50, i-ioo, 1-150, 

 and 1-200. The probable presence of the typhoid 

 bacillus was manifest by the formation of flocculi within 

 a quarter of an hour, and agglutination was complete in 

 from two to five hours. 



The tube having the greatest dilution in which aggluti- 

 nation was apparent was then examined by breaking off 

 the lower end, containing the precipitate, washing the 

 sediment two or three times with sterile water after 

 removing the clear supernatant liquid, and allowing the 

 bacteria to settle again. The organisms remaining were 

 plated upon various media, and examined biochemically 

 to determine their true character., It was found that a 

 dilution of i to 60 was the highest which could be used 

 with the organisms examined, and it is therefore prob- 

 able that high dilutions (greater than 1-60) cannot be 

 successfully used. 



A study of the organisms isolated in this case was 

 made .by Klotz (1904), who found the culture to be 

 not a typical B. typhi but a form showing certain 

 points of similarity to both B. typhi and to B. coU, and 

 probably intermediate between them. As this author 

 pointed out, it is therefore evident that even when a 

 positive result is obtained with a relatively high dilution 

 of typhoid serum it is unwise to regard the action as 

 absolutely specific. 



