THE PROBLEM OF VIRULENCE 5 



gations of Frosch 1 have shown that diphtheria bacilli may often be 

 found in blood and organs of diphtheritic patients, and tetanus 

 bacilli have occasionally been found in the spleen. However, such 

 distribution is not necessary for the production of disease by these 

 bacteria, and the essential point remains that they may cause violent, 

 often fatal, disease without truly departing from their saprophytic 

 mode of life upon dead tissues. Between the saprophytes and the 

 true parasites or invaders of living tissue many transitions occur, 

 and the condition of parasitism is probably a form of specific adap- 

 tation. 



How such transition may be biologically developed is probably 

 well illustrated by the investigations of Italian bacteriologists upon 

 tetanus bacilli. 2 Tarozzi 3 inoculated guinea pigs and rabbits with 

 tetanus spores subcutaneously and found that these spores were 

 rapidly transported to the liver, spleen, and kidneys, where they 

 could maintain a latent existence for as long as 51 days. If during 

 this period trauma or any injury of the organs was practiced which 

 led to the formation of necrotic tissue the spores would develop upon 

 this basis and cause acute or chronic tetanus. Canfora, 4 continuing 

 these studies, likewise found that tetanus spores inoculated under the 

 skin are rapidly distributed throughout the circulation. If no 

 trauma has taken place at the point of inoculation the locally lodged 

 spores may be rapidly destroyed, probably by phagocytosis. In the 

 circulation they appear to be less rapidly eliminated and may be 

 present for from ten to thirteen days. If, during this period, there 

 is produced a small wound, blood clot, or necrotic area in the body 

 this may serve as a focus for development and tetanus may ensue. 

 After ten or more days the spores disappear from the blood, but may 

 then take up a latent existence in some of the organs as stated by 

 Tarozzi. Apart from their importance as constituting a sort of 

 . transitional condition between pure saprophytism and parasitism, 

 these investigations would seem to have much bearing upon the so- 

 called cases of a cryptogenic tetanus." 



True infection, that is, the invasion of one species by individuals 

 of another, and the ability of the latter to multiply and functionate 

 within the cell complexes of the former, is a process quite out of 

 keeping with the ordinary plans of nature, throughout which there 

 seems to be a distinct opposition to the colonization and functiona- 

 tion of one living being within the living substance of another. 

 Thus, as Bail 5 has pointed out, a mass of frogs' eggs will remain 



1 Froseh. Zeitsdir. f. Hyg., Vol. 13, 1893. 



2 Belfanti, quoted from Canfora, Centralblt. f. Bact., I. Orig. Vol. 45, 

 1908. 



3 Tarozzi. Centralblt. f. Bact., Orig. Vol. 38, 1905. 



4 Canfora. Centralblt. f. Bact., Orig. Vol. 45, 1908. 



5 Bail. "Das Problem der Bakt. Infection." Klinkhardt, Leipzig, 1911. 



