ISOLATION OF SPECIFIC PATHOGENES 77 



by Gaehtgens (Gaehtgens, 1905) by the addition of 

 caffein, and he found it of great service in isolating the 

 typhoid bacillus from stools of patients suffering with 

 the disease. No attempts were made by him to isolate 

 the organism from polluted water. 



Loeffler (Loeffler, 1903 and 1906) and Lentz and 

 Tietz (Lentz and Tietz, 1903 and 1905) have made use 

 of an agar medium containing malachite green. This 

 medium is supposed to inhibit the growth of B. coli 

 while favoring B. typhi, and has been recommended 

 for the isolation of the organism from faeces. Dcebert 

 (Dcebert, 1900) has shown that certain varieties of 

 ma!achite green are not suited to this purpose. Nowack 

 (Nowack, 1905) has also pointed out the same fact, 

 and ascribed the difference to the presence of dextrin. 

 He also showed that a medium 0.8 per cent alkaline to 

 phenol-phthalein is more favorable to B. typhi and 

 less favorable to B. coli than one neutral to litmus. 

 With such a medium he found that about 20 per cent 

 of the typhoid bacilli present develop. Lemke (1911) 

 has recently reported good success in isolating typhoid 

 and para-typhoid bacilli from artificially infected 

 waters by the use of nutrient broth containing 3-5 

 per cent of sodium chloride and varying amounts of 

 malachite green as an enrichment medium. 



The use of the inhibitive anilin dyes like crystal 

 violet and malachite green has the disadvantage of also 

 inhibiting to some extent the development of the weaker 

 typhoid organisms. Another principle is involved in 

 the media proposed by Hiss and Hesse. These are 

 both agar media of lower spissitude than ordinary 



