350 TYPHOID FEVER. 



fever after exposure to natural infection must rest on 

 experience, but as most of those who have been subjected 

 to it are medical officers in the British services, who are 

 likely to be exposed to such infection abroad, this ex- 

 perience may soon be gained. It has been found in cases 

 where the method has been practised that in the course of 

 a fortnight a positive Widal's reaction was obtained, and 

 such an occurrence is probably evidence of the acquisition 

 of a certain degree of immunity. 



Anti-typhoid Serum. Bokenham grew virulent typhoid bacilli for 

 three weeks on bouillon containing ten per cent of alkali albumin, and 

 filtering the cultures through porcelain obtained a filtrate which, 

 though non-toxic to guinea-pigs, probably had immunising properties. 

 Starting with this and afterwards using it alternately with killed 

 cultures, he immunised a horse and found that the serum had neutral- 

 ising power for typhoid bacilli when the latter mixed with it were 

 injected into guinea-pigs. When injection of the serum was followed 

 by injection of bacilli, the pathogenic action of the latter was to a 

 certain extent prevented, and there was also evidence of the serum 

 possessing curative properties. 



Methods of Examination. The methods of microscopic 

 examination, and of isolation of typhoid bacilli from the 

 spleen post mortem, have already been described. They may 

 be isolated from the Peyer's patches, lymphatic glands, etc. 

 by a similar method. 



During life, typhoid bacilli may be obtained in culture 

 in the following ways : 



(a) from the Spleen. This is the most certain method 

 of obtaining the typhoid bacillus during the continuance 

 of a case. The skin over the spleen is purified and, a sterile 

 hypodermic syringe being plunged into the organ, there is 

 withdrawn from the splenic pulp a droplet of fluid, from 

 which plates are made. In a large proportion of cases of 

 typhoid the bacillus may be thus obtained, failure only 

 occurring when the needle does not happen to touch a 

 bacillus. Numerous observations have shown that pro- 

 vided the needle be not too large, the procedure is quite 

 safe. Its use, however, is scarcely called for. 



