Modes of Bacterial Pathogenesis 69 



ability to overcome the body defenses. This may indicate 

 activity of the infecting organism, or weakness of the defen- 

 sive mechanism. The relation of these factors is exceedingly 

 complex, only partly understood, and will be fully discussed 

 in the chapter upon Immunity. 



The toxic power of the bacteria is intrinsic in the micro- 

 organisms themselves. 



For convenience toxins may be described as intracellular 

 or insoluble, and extracellular or soluble. 



The intracellular toxins. These products are but little 

 known and have only recently begun to attract attention. 

 Their insoluble nature makes it difficult to isolate them, and 

 determines the limitations of their activity. Until the in- 

 vestigations of Vaughan, Cooley and Gelston,* and later 

 Vaughan and his associates, Detweiler,f Wheeler, J Leach, 

 Marshall and Gelston, || Gelston,** and J. V. Vaughan, ff 

 Wheeler, J{ Leach, Mclntyre, |||| and others, it seemed re- 

 markable that micro-organisms whose filtered cultures con- 

 tained little demonstrable toxic substance are sometimes able 

 to produce active pathologic activities. By means of special 

 apparatus in which the micro-organisms could be cultivated 

 in enormous quantities, and the disintegration of the micro- 

 organismal masses secured by subjecting them to high tem- 

 peratures or to the action of mineral acids, it was discovered 

 that the colon bacilli, typhoid bacilli, and many supposedly 

 harmless bacteria, contain intensely active toxic substances. 

 In all probability some of the toxic substances produced by 

 such means are artefacts, but enough work has been done 

 to prove that insoluble toxic substances are undoubtedly 

 present in such organisms, and the toxic substances obtained 

 by the comminution of culture masses made solid and 

 brittle by exposure to liquid air, as suggested by Macfadyen 

 and Rowland; the autolytic digestion of bacteria washed 

 free of their culture fluids and suspended in physiological 

 salt solution, and the dissolution of bacteria by bacteriolytic 

 animal juices have corroborated the original conclusions. 



* "Journal of the American Medical Association," Feb. 23, 1901; 

 "Trans. Assoc. Amer. Phys. " 1901, and "American Medicine," May, 

 1901. 



t " Trans. Assoc. Amer. Phys.," 1902. J Ibid. 



Ibid. || Ibid. ** Ibid. 



ft Ibid. JJ "Jour. Amer. Med. Assoc.," 1904, XLII, p. 1000. 



Ibid., p. 1003. || || Ibid., p. 1073. 



