C.-E. A. WINSLOW 8i 



ination showed these organisms in 62 per cent of the cases studied while objects re- 

 cently handled (door handles, push buttons, etc.) showed them in 42 per cent of the 

 cases. On locations such as walls six feet above the ground, the undersides of chairs 

 and tables and the like, these organisms were isolated in 10 per cent of the cases. 



From the standpoint of epidemiology, it is essential to note that the pathogenic 

 bacteria which survive for such long periods as those noted above are so few in number 

 that their presence is of little or no practical significance for disease transmission. 

 Houston (1908), for example, was able to isolate typhoid bacilli from water after nine 

 weeks; but 99.9 per cent of the bacteria originally present had perished after one week. 

 Nothing is of course more certain than the fact that transmission of disease germs oc- 

 curs in the vast majority of instances only through the rather direct and immediate 

 transfer of fresh body discharges. 



In the earlier days of bacteriology it was customary to refer to the few pathogenic 

 bacteria which survive after long periods of time in water or earth as representing a 

 "resistant minority." It is quite possible that in certain instances a selection of more 

 resistant variants may in fact take place. Sedgwick and Winslow (1902) showed that 

 individual strains of typhoid bacteria differ markedly in their ability to survive in 

 ice; and Ayers and Johnson (191 5) found that various strains of colon bacilli show 

 great differences in their ability to resist various pasteurization temperatures. There 

 is, however, no direct evidence that the cells which die out toward the end of the cycle 

 of bacterial population derived from a single strain are intrinsically more resistant 

 than those which perish earlier; and it seems probable that the curve for such a cycle 

 is mainly determined by a series of catenary reactions following the ordinary laws of 

 more simple chemical processes. 



BIBLIOGRAPHY 

 Allen, P. W.: J. Bad., 8, 555. 1923. 



Ayers, S. H., Cook, L. B., and Clemmer, P. W.: U.S. Bureau of Animal Industry, U.S. De- 

 partment of Agriculture, Bull. 642. 

 Ayers, S. H., and Johnson, W. T.: ibid., Bull. 126. 

 Ayers, S. H., and Johnson, W. T.: /. Agric. Research, 3, 401. 1915. 

 Barber, M. A.: /. Infect. Dis., 5, 379. 1908. 

 Bigelow, W. D.: ibid., 29, 528. 1921. 

 Brooks, S. C: J. General Physiol., i, 61. 1918. 

 Buchanan, R. E.: J. Infect. Dis., 23, 109. 1918. 



Buchner, H., Langard, K., and Riedlin, G.: Centralbl.f. Bakteriol., 2, i. 1887. 

 Buddin, W.: /. Agric. 5c., 6, 417. 1914. 



Burke, V., Sprague, A., and Barnes, L.: /. Infect. Dis., 36, 555. 1925. 

 Chapin, C. V.: Sources and Modes of Infection. New York, 1912. 

 Chesney, A. M.: /. Exper. Med., 24, 387. 1916. 

 Chick, H.: /. Hyg., 8, 92. 1908. 

 Chick, H.: ibid., 10, 237. 1910. 

 Chick, H.: ibid., 12, 414. 191 2. 

 Chick, H., and Martin, C. J.: ibid., 8, 654. 1908. 

 Chick, H., and Martin, C. J.: /. Physiol., 40, 404. 1910. 

 Clark, P. F., and Ruehl, W. H.: /. Bad., 4, 615. 1919. 

 Cohen, B.: ibid., 7, 183. 1922. 



