2O6 LOUISE H. GREGORY. 



B. THE AFTER EFFECTS OF BEEF FEEDING ON PROTOPLASM OF 



DIFFERENT AGES. 



In a number of experiments after a series had been kept in the 

 beef-flour medium for ten days, one individual from each of the 

 five lines of the series was put back into normal medium and the 

 division rate of the new series compared with that of the series 

 continued in the beef-flour medium. 



Three young. series after ten days in the beef medium were 

 transfered to normal medium and in every case the vitality was 

 increased to such an extent that it exceeded that of the beef series 

 and equaled that of the normal control series. In other words 

 the depression while in the beef medium was followed by a 

 stimulation on the return to normal medium. 



Four mature series were treated in the same manner some twice 

 and others three times, and in one experiment only was there any 

 indication of a stimulus when the series was transfered from the 

 beef to normal medium. In five experiments the transfer was 

 followed by a distinct lowering of the division rate and in three 

 other experiments, there was no change in vitality as indicated by 

 the division rate. 



Finally series 95 and 97 were tested twice each in their old age 

 and in all four experiments the transfer to normal medium was 

 followed by a distinct increase in vitality. 



Here again is seen the similarity in the behavior of immature 

 and worn out protoplasm. In both cases there is an immediate 

 depression of the life processes when treated with the beef, but 

 this depression disapears on removal to normal conditions and in 

 some cases there follows a period of higher vitality, the real effect 

 of the beef being only delayed in its appearance. On the other 

 hand the mature individuals respond immediately with a more 

 rapid division rate which falls when the stimulus is removed and 

 the medium is again normal. Immature protoplasm and 

 protoplasm of old age are apparently not able to adjust themselves 

 quickly to changes in the environment. They are at once 

 depressed in the new condition but overcome the depression 

 when back in normal medium and often show a quickened 

 vitality. Mature protoplasm is like a healthy muscle that is 

 always in tone, ready to respond to a stimulus and needs no time 



