582 PR0CEEDINC4S OF SECTION I. 



With this general introduction I wish now to consider first of 

 all certain points of bacteriological technique, and then to give a 

 short summary of the steps necessary in the handling of such 

 investigations both epidemiologically and bacteriologically. As 

 regards bacteriological technique, it is as well here to introduce 

 a word of caution against widely prevalent ideas that it is a matter, 

 with ordinary media, of great difficulty to isolate and differentiate 

 the typhoid bacillus, and that consequently certain special plating 

 methods are necessary. Nothing shows the weakness of such 

 special plates invented by enthusiasts who wish to make a short- 

 cut method to pick out the typhoid bacillus than does the large 

 number of these "selective" or "enrichment" plates, all of 

 which are lauded by their own particular inventor. Ledingham, 

 who is undoubtedly one of the greatest authorities on the bac- 

 teriology of typhoid, says, " Thei'e is no royal road to the isola- 

 tion of the bacillus." The truth Js, according to him, that there 

 is probably not much to choose between any methods, but that 

 if one has mastered any particular technique he will get better 

 results by that than by a method he knows less well. Ledingham 

 uses bile-salt neutral red lactose agar, a very easily prepared and 

 simple medium, which differentiates lactose fermenters from non- 

 lactose fermenters, and enables one to pick off the white non- 

 lactose fermenting colonies. I am strongly of the opinion that this 

 separation is all that occurs with most of the typhoid selective 

 plates, and the good results claimed by some authors, and not 

 obtained by others, are explainable on the degree of proficiency 

 shown by one or other authority with a particular method. 

 Ordinary agar plates in my hands seem to give as good results 

 cts any; but it no doubt takes some practice before one can differ- 

 entiate a non-lactose fermenting colony with certainty, and there- 

 fore it is usually necessary to pick off a large number of colonies 

 for testing. Probably the simplest method for general purposes 

 is the bile-salt neutral red agar plate. This medium should, how- 

 ever, be occasionally tested side by side with ordinary agar to be 

 sure. B. typhosus will grow equally well, for in certain samples it 

 seems to possess a considerable power of inhibiting B. typhosus. 



When it comes to such a pass that a special plating medium, 

 admitted by the author (1) to be difficult to prepare, is advo- 

 cated for blood culture work, although such records as Tebbutt's 

 (2) show that in the vast majority of bile cultures from blood the 

 bacillus is recovered in pure culture, and can be identified by 

 direct inoculation on to sugars, agar, &c., it is seen that the 

 above caution against unnecessary complication of method is not 

 without good reason. Blood cultures are made very satisfactorily, 

 in my opinion, by squirting directly from the sterile syringe with 

 which the blood is collected from the median basilic vein about 



