SPECIFIC AND NONSPECIFIC RESISTANCE 



an organism isolated from a low temperature acclimatized animal 

 can grow equally well at the optimal temperature of 37° C or at 

 reduced incubation temperatures of 32° C, whereas the organism 

 isolated from an animal kept at 21° C does not have this dual 

 growth capacity. 



The situation becomes more confusing when one looks at the 

 oxygen uptake curves. When both the isolated strains of organisms 

 are incubated at 37° C, the oxygen uptake curves are similar qual- 

 itatively and quantitatively (Figure 7). When both isolated strains 

 of organisms were incubated at 32° C, the oxygen uptake of the 

 K. pneumoniae isolated from the low temperature acclimatized 

 animals was greater than that of the organisms isolated from mice 

 maintained at 21° C. This is what one would expect since the growth 

 curves exhibit these same changes ; however , note that quantitatively, 

 the amount of oxygen uptake for both isolates is approximately one- 

 half when incubation is carried out at 32° C compared to 37° C. 

 This implies that the isolate from the mice kept at 2° C is more 

 efficient metabolically since it can grow as rapidly at 32° C as it 

 can at 37° C, yet requires only one- half the amount of oxygen to 

 do so (Fig. 8). 



The LD5Q values of both isolates are summarized in Table I. 

 No significant differences or changes in the virulence of the 

 organisms were observed. 



Mouse temperature measurements. In order to determine the 

 effect huddling had on mouse temperature measurements, the 

 following experiment was conducted. Mice were placed at 2° C or 

 21° C in cages containing either a single mouse or a group of five 

 mice. Core, sMn, and upper respiratory cavity temperatures were 

 taken hourly for the first four to five hours on the first day, then 

 once a day for 8 to 14 days, and finally on the forty- fifth day of 

 exposure. Figure 9 shows that the presence of five mice in one 

 cage at 2° C results in temperature measurements that increase 

 gradually, reaching an initial maximum in 2 to 4 hours after ex- 

 posure. Generally, the rectal temperature is consistently higher 

 than the upper respiratory cavity, but it does not appear to be 

 significantly greater. The skin temperatures are considerably less 

 than the rectal or upper respiratory cavity temperatures, so the 



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