Pathogenesis 497 



several times washed in distilled water, and then allowed 

 to macerate in normal salt solution, autolysis takes place 

 and a toxin is liberated, showing that the toxin is intracel- 

 lular. Macfadyen and Rowland* liberated an intracellular 

 toxin from cultures of the typhoid bacilli by freezing them 

 with liquid air and grinding them in an agate mortar. Ani- 

 mals immunized with this poison produced an anti-serum 

 active against it, but useless against infection with typhoid 

 bacilli. Wright, of Netley,f observes that Macfadyen's 

 method of securing this intracellular toxin was unneces- 

 sarily cumbersome, as the body juices of animals injected 

 with dead cultures of the bacilli dissolve them at once and 

 thus liberate the same toxic product. 



Invasion of the Body. The typhoid bacillus probably, 

 in the great majority of cases, enters the alimentary tract 

 with infected food and water, but may at times be in- 

 haled (Klemperer and Levy). 



Pathogenesis. It is almost universally believed that 

 infection by the typhoid bacillus takes place through 

 polluted drinking-water, and the epidemiology of the dis- 

 ease seems to point unmistakably in that direction. In 

 favor of it as the almost invariable result of purifying the 

 drinking-water is diminution of the number of cases or 

 disappearance of the disease. Opposed to it are the almost 

 invariable failure of bacteriologists to discover the typhoid 

 bacillus in waters thought to be extremely dangerous, and 

 our knowledge of the rapidity with which the typhoid 

 bacillus becomes extinguished in waters containing other 

 micro-organisms. In elaborate experimental studies of 

 this question Jordan, Russell and ^eitj found its longevity 

 to be only three or four days under conditions simulating 

 as nearly as possible the conditions found in nature. 



The primary operations of the typhoid bacillus are un- 

 known. The resisting power of the organism permits it to 

 pass uninjured through the acid secretions of the stomach 

 and to enter the intestine, where the chief local disturbances 

 are set up. Whether during an early residence in the intes- 

 tine its metabolism is accompanied by the formation of a 

 toxic product, irritating to the mucosa, and affording the 

 bacilli means of entrance to the lymph-vessels through 



*"Brit. Med. Jour.," 1903. 

 f'Brit. Med. Jour.," April 4, 1903, I, p. 786. 

 J " Journal of Infectious Diseases," 1904, i, p. 641. 

 32 



