438 PROCEEDINGS OF THE ACADEMY OF [1881. 



niont of the micrococcus itself; the second, the best for the 

 obtaining of it in quantity for experimentation. 



Micrococci were cultivated from the surface of ordinary sore 

 thruats, from furred tongue, from cases of mild diphtheria as 

 commonly seen in Philadelphia, and from Ludingtou cases. 

 There were no diflerences to be detected in the general or special 

 appearance of the various micrococci, and no constant differences 

 in size. They all formed similar shapes in the culture-apparatus ; 

 they had this difference, however, — whilst the Ludington micro- 

 cocci grew most rapidly and eagerly, generation after generation 

 up to the tenth, those from Philadelphia diphtheria ceased their 

 growth in the fourth or fifth generation, whilst those taken from 

 furred tongue, never got beyond the third transplantation. 

 Various culture-fluids were used, but the results were identical. 

 They concluded, therefore, that as no difference is detectable 

 between the micrococci found in ordinary sore throat and those 

 of diphtheria, save only in their reproductive activity, they are 

 the same organisms in different states. As the result of some 

 hundreds of cultures, they believe that the vitality under artificial 

 culture is in direct proportion to the malignancy of the case 

 from which the plant has been taken. 



They next made a series of experiments of inoculating rab- 

 bits with cultivated micrococci, and succeeded in producing 

 diphtheria with the second generation, but never with an}- later 

 product. This success, taken in conjunction with the urine 

 experiments already spoken of, seemed sufficient to establish the 

 fact that the micrococci are theyb??.s et origo mali of diphtlieria. 

 The experiments of Pasteur and others have proven that it is 

 possible for an inert organism to be changed into one possessed 

 of most virulent activity, or vice versa, and it was believed that 

 direct proof could be offered that the micrococci of the mouth 

 are really identical in species with the micrococci of diphtheria, 

 and do not merely seem to be so. The Ludington membrane 

 was exposed for some weeks to the air in a dried condition. 

 There was no putridity or other change detectable in it ; but, 

 whereas formerly it had been most virulent, now it was inert, 

 and its micrococci not only looked like those taken from an 

 ordinary angina, but acted like them. They were not dead, they 

 had still power of multiplication, but they no longer grew in the 

 culture-fluid beyond the third or fourth generation. Certainly 

 they were specifically the same as they had been, and certainly, 

 therefore, the power of rapid growth in culture-fluids and in the 

 body of the rabbit is not a specific character of the diphtheria 

 Micrococcns. 



As is well known, Pasteur attributes the change from an active 

 to an inert organism to the influence of the oxygen of the air 

 upon the organism. Whether this be true of the diphtheria 

 Micrococcus is uncertain, but the effects of exposure of the dried 

 membrane seem to point in such direction. 



