450 GEO. T. HARGITT AND WALTER W. FRAY 



Such an attempt was a part of our program but we were not 

 able to carry it out, on account of lack of time to give to it. 



Any attempt to correlate the characteristics of the bacteria 

 with their favorableness or unfavorableness as food leads to little. 

 From the table of bacteria it appears that a majority of the bac- 

 teria which were recovered from abnormal infusions were of a 

 spreading or running type of growth. It was bacteria of this 

 type which produced the putrefactive or fermentative odors 

 when grown in hay infusions, and when used in pure cultures as 

 food for Paramecium the latter soon died. Any culture fluid 

 which has any considerable number of this type of bacteria is 

 therefore apt to be a very unfavorable medium in which to 

 grow Paramecium. 



CONCLUSIONS 



The principal points brought out by this investigation may be 

 summarized as follows: 



1. Bacteria present in hay infusions gain access from the hay, 

 from the water, or from the air. Some forms may be intro- 

 duced from all three sources, others only from a single source. 



2. Both normal and abnormal (fermenting and putrefying) 

 hay infusions were analyzed and the predominant types of bac- 

 teria present were obtained in pure cultures by bacteriological 

 methods. The characteristics of some of the bacteria isolated 

 are tabulated in a table at the end of the paper. A total of 30 

 different bacteria were isolated in pure cultures. 



3. The bacterial flora of a hay infusion changes when the 

 infusion is allowed to stand without adding fresh hay and water. 

 Analyses made at the end of a few days, at the end of a few 

 weeks, and again after four months showed a different flora 

 each time. In old cultures colonies with amoeboid or lobose 

 type of growth, and capsulated forms are present in great 

 abundance. 



4. Hay infusions and beef extract solutions when sterilized 

 in the autoclave at a temperature of about 130°C. are so modified 

 by the high temperature as to be unsuitable as a culture medium 

 for Paramecium, since in these fluids the animals died in a short 



