198 BACTEKIOLOGY OF THE EYE 



which can be demonstrated. Are we justified in assuming that this function is 

 latent in the conjunctival xerose bacilli ? 



There are records of a virulent bacilli having been made virulent in other parts 

 of the body. Trumpp did this in the case of a bacillus from pleuritic pus by 

 mixing it with diphtheria toxin ; he then obtained full virulence. We know that 

 Eoux and Yersin exalted a diphtheria strain by inoculating it along with Strepioco<-<-i. 

 Trumpp's results are not yet confirmed, and such a record cannot be taken as 

 decisive, seeing that the organisms in question, though formerly virulent, were 

 then avirulent, and they were merely again acquiring their virulence, and this 

 cannot be taken as applying to the B. xerosis, which may never have been virulent. 



The symbiosis recorded by Roux and Yersin rather opposes the idea that the 

 B. xerosis can develop virulence, as these two organisms (B. xerosis and Strepto- 

 coccus) are occasionally observed together on the conjunctiva without any such 

 development of virulence. Escherich, however, never succeeded in developing 

 virulence in pseudo-diphtheria bacilli by inoculating them with Streptococci. It 

 is interesting to note that Gelpke made the same experiments without obtaining 

 any results. 



Doetsch found a B. xerosis which was pathogenic for mice, and its virulence 

 increased by passage through the animal and further cultivation. 



Such isolated records prove nothing. And it should be noted that pathogenicity 

 for mice is not identical with the production of true diphtheria toxin ; neither has 

 it been shown that the animals died in the typical way, nor were immunizing 

 experiments with antitoxin carried out. 



Nor can we consider the observations of C. Frankel, Peters, and Schanz of any 

 greater importance. They report that a long time after the injection of very large 

 doses the animals died. This need not indicate a diphtheritic virulence in the 

 B. xerosis. Such, indeed, is not death from diphtheria. Antitoxin does not prevent 

 such results (Spronk). In conjunction with Bietti and Naito, and working with 

 large doses of 120 different strains, I only once had a fatal result, though that, indeed, 

 was a rapid death, as in diphtheria. In this case we had to do with the rare but still 

 well-known occurrence of a virulent diphtheria strain upon the healthy conjunctiva. 



De Simon's experiments, in which he obtained a virulent organism from a 

 so-called pseudo- diphtheria bacillus by growing it on tetanus media, is not a proof 

 beyond the possibility of error. 



Schanz contrasts the clinical facts that in mild conjunctival catarrh virulent 

 diphtheria bacilli can be found, and in pseudo-membranous conjunctivitis aviru- 

 lent bacilli are often seen. This is very strong evidence against the pathogenicity 

 of the diphtheria bacilli, but shows that membranes, etc., are good media for the 

 growth of such organisms. 



That virulent bacilli are occasionally found upon the conjunctiva when it is only 

 slightly inflamed (Wagner, A. v. Hippel, Frankel, Pes, Sourdille), and even when 

 healthy (Pilcher, McKee), is not incompatible with their pathogenicity. (Infection 

 with a virulent strain of a pathogenic Bacterium does not necessarily produce the 

 disease in every case, and when the disease does occur we find slight and severe 

 cases, depending on the susceptibility of the individual. 



Further comprehensive series of experiments are necessary to prove whether 

 there is any capacity in the xerose bacilli of developing into virulent diphtheria 

 organisms. 



Every attempt to immunize susceptible annuals against the poison of diphtheria 

 by means of the B. xerosis has so far failed. Gelpke, and also Bietti, 1 have made 



1 Duane and Hastings are in error in their opposition to Bietti (loc. cit.), on the ground 

 of his ascribing too great an importance to the Batittvx xerosis in the etiology of con- 

 junctivitis. Bietti is much more inclined to the opposite view. 



