STREPTOCOCCUS HEMOLYTICUS 175 



A search through the hterature reveals the fact that the 

 latent period or lag phase has received the bulk of the attention 

 of workers in this field. Miiller (1896) perhaps was the first to 

 recognize the phenomenon while working with cultures of Bact. 

 typhosum at temperatures simulating febrile conditions. The 

 duration of lag was found by him to vary with the age of the 

 culture used for seeding, being shorter for young than for older 

 cultures. He beUeved the phenomenon to be the result of an 

 alteration of the cells sustained upon transplantation to a new 

 medium, the duration of lag representing the time required for 

 the organisms to recover from the injury. Rahn (1906), working 

 with Ps. fluorescens, studied the influence upon lag of the amount 

 of inoculum and concluded that the larger the number of organ- 

 isms used for seeding, the shorter the lag. Penfold (1914) later 

 demonstrated that this effect held, up to a certain limit, beyond 

 which an increase in the amount of inoculum exerted no influence 

 upon the duration of the lag period. In case of small inocula, 

 however, Penfold showed that a diminution in amount of seed 

 invariably caused a lengthening of lag. He found that older 

 cultures caused lengthening of lag only up to a certain point, for 

 example, a four-day culture gave the same duration of lag as a 

 twelve-day culture in the case of Bact. coli. Barber (1908) 

 working with single cells {Bad. coli) was the first to show that 

 under proper conditions lag may be eliminated. He used 

 rapidly dividing cells which were accustomed to the medium 

 employed and was able to find no evidence of inhibition upon 

 transplantation. This observation has received substantiation 

 at the hands of Penfold (1914), Chesney (1916), and Salter 

 (1919), all of whom worked with Bact. coli. Coplans (1909) 

 also states that with Bact. coli, there is ordinarily no absolute 

 lag upon transplantation to a favorable medium. New milk 

 ordinarily possesses inhibitory properties but this investigator 

 found that heating momentarily to 100°C. caused a disappear- 

 ance of this special inhibitory quality. Salter (1919) found also 

 that the age of the parent culture exerted a considerable influence 

 upon the duration of lag, thus confirming the observations of 

 previous investigators. Lane-Claypon (1909) has studied the 



