G70 PATHOGENIC MICROORGANISMS 



ticularly the studies of Conradi and Drigalski 77 the paper of Sacquepee, 78 

 the summary given by Kutscher 79 in the Second Edition of the Kolle 

 and Wassermann Handbook, the summary of Gay in the book men- 

 tioned above, and the article by Garbat, not yet published, but about to 

 appear as one of the Monographs of the Rockefeller Institute. The 

 first definite suggestion of the danger of typhoid infection emanating 

 from convalescents long after the disease itself had been cured, came 

 from Koch. 80 He based this opinion at first upon purely epidemiological 

 evidence, but in 1904 Drigalski 81 began to isolate bacilli from individuals 

 who were apparently in complete health. Sacquepee 78 classifies 

 typhoid carriers chiefly into convalescent carriers who become free of 

 the bacilli within three months after the termination of their disease, 

 and chronic carriers who continue to harbor the bacilli for many years, 

 and perhaps permanently. In addition to this, there are a certain 

 number of so-called healthy carriers in whom no history of their ever 

 having had the disease can be adduced. 



The distinction between a temporary carrier and a chronic carrier 

 must, of course, be to a certain degree arbitrary, but in general it may 

 be said that in most typhoid cases the organisms disappear from the 

 urine and feces within from six weeks to three months after recovery. 

 Sacquepee classifies as chronic carriers only those in which the organisms 

 are still present three months after complete recovery. After this 

 period, the length of time to which the carrier may persist is variable, 

 depending upon whether or not chronic lesions are established. These 

 will be discussed below. The frequence with which chronic carriers 

 following typhoid fever occur may be gathered from the table compiled 

 by Gay and published in the book mentioned above. 



If we consider that the figures presented in this table must neces- 

 sarily represent underestimates because of the technical difficulties 

 attending the discovery of small numbers of typhoid bacilli, it becomes 

 apparent that the number of potential foci for infection in a community 

 is enormous. Gay estimates, on a basis of a 5 per cent minimum, that 

 we have 7500 added annually to the carriers present in the United 

 States. On this basis about 0.2 per cent to 0.3 per cent of the general 

 population may be assumed to be carriers. 



According to the foci upon which the carrier state depends, typhoid 



77 Conradi and Drigalski, Zeit. f. Hyg., 34, 1902, 283. 



78 Sacquepee, Bull, do I'lnst. Past,, 8, 1910, 521 and 689. 



79 Kutscher, Kolle and VVassonnann Ilandbuch, 2d Edition, Fischer, Jena, 1913. 

 Koch, Ver. a. d. Militarsanitatswesen, H. 21, 1902. 



81 Drigalski, Cent. f. Bakt,, 35, 1904, 776. 



