ETIOLOGY 



1367 



each of these germs, and certain characters have been given in 

 Chapter XXXVI., p. 934. Of the B. typhosus, for instance, two 

 varieties can be easily differentiated — one rendering milk alkaline 

 after an initial acidity; the other making milk permanently acid. 



Of B. paratyphosus B several varieties have been described by 

 Castellani, Alcock, and others. As regards the so-called B. 

 typhosus C, this term, used by several observers, among whom 

 recently Hirschfeld, covers different germs, one ot which is sero- 

 logically identical with B. aertryke. 



With regard to theB. typhosus of Eberth, it is found in the intes- 

 tine, not merely during the attack of fever, but during the incuba- 

 tion, and for a period extending perhaps as long as thirty years 

 after an attack — -that is to say, the bacillus has been grown from the 

 faeces of a person thirty years after an attack of enteric fever; but 

 whether it had existed in the bowels for the whole period is naturally 

 not known, but it is possible. In other words, the bacillus can live 

 in the bodies of people for years after an attack. These people 

 are reservoirs or carriers of the bacillus, and may be called intes- 

 tinal carriers. People who pass the bacilli in their faeces during 

 the period of incubation are called precocious intestinal carriers ; 

 the patients passing the bacilli during the attack and convalescence 

 are called acute intestinal carriers ; while people who continue to 

 pass the bacilli in their f^ces for a year or less than a year after 

 an attack of enteric fever are called temporary or transitory intes- 

 tinal carriers ; and those in whose faeces the bacilli are found after 

 an interval of longer than a year are called chronic intestinal carriers. 



In addition, there are carriers who are not known to have had 

 an attack of typhoid; that is to say, there may be people in whom 

 the B. typhosus Eberth may live for an unknown period without 

 showing any pathological signs at any time. These are known as 

 paradoxical intestinal carriers. This is possible, but it is also prob- 

 able that some of the carriers in question may have been cases of 

 ambulatory typhoid, and therefore really belonged to the class of 

 chronic intestinal carriers. As to the habitat of the bacilli while 

 in the carrier, it seems that the gall-bladder is of the greatest 

 importance, while during the actual attack of fever the bacilli are 

 to be found not merely in the intestinal contents, but also in the 

 mesenteric glands, the spleen, and the circulating blood. Now, 

 the proportion of female carriers to male carriers is as five is to one. 

 This is a curious fact, and, moreover, the bacillus is often found in 

 the gall-bladder. Now, the frequency of gall-stones in women as 

 compared with men is as three is to one; further, it is a well-known 

 fact that gall-stones are often discovered for the first time at an 

 autopsy; in fact, it is believed that only 10 per cent, of the persons 

 suffering from gall-stones show any sign of the disease during life, 

 and it is a curious fact that the percentage of persons showing signs 

 of gall-stones after an attack of enteric fever is 14 per cent. 



All these factors considered together, along with the known fact 

 that B. typhosus has been isolated on several occasions from the 



