RESPIRATORY METABOLISM 365 



organisms whose normal environment is high in CO. might depend 

 more on CO, buffering than those the normal environment of which 

 is low in COo. (For possible application of this idea to culture of in- 

 testinal forms, see Jahn, 1934). 



4. THE EFFECT OF THE PHYSIOLOGICAL STATE ON Og CONSUMPTION 



It seems as if the effect of various factors which influence the physio- 

 logical state of an organism may be reflected in measurements of O^ 

 consumption. Factors which have been investigated for the Protozoa are 

 starvation, age of the culture, and conjugation. 



Lund (1918c) starved Paramecium in tap water and noted an ap- 

 preciable decrease in respiration during the first twenty hours. This was 

 simultaneous with the disappearance of deutoplasmic food reserves from 

 the protoplasm. Upon feeding starved animals with boiled yeast sus- 

 pensions, the rate of oxygen consumption could be increased two to 

 three times. This increase was independent of cell division. Leichsenring 

 ( 1925 ) demonstrated a decrease of 23 percent after twenty-four hours of 

 starvation and 29 percent after seventy-two hours. 



The effect of the age of the culture on O2 consumption was first 

 studied by Wachendorff ( 1912) , who found that for Colpidium colpoda 

 the O, consumed per organism diminished from 191 mm^ per hour 

 the first day to 151 mm' the tenth day, and to 59 mm' on the thirtieth 

 day. Reidmuller (1936) reported a higher rate of O, consumption for 

 young cultures of Trichomonas foetus than for older cultures. Twenty- 

 four to forty-eight-hour-old cultures consumed 4.3 mm'' O, per mm'' of 

 organisms, sixty-hour cultures, 2.8 mm,' and three-day-old cultures only 

 0.81 mm' O,. Andrews and von Brand (1938) reported a decrease 

 in sugar consumption per organism for this species, with increasing age 

 of the culture, and their data indicate that the differences observed by 

 Reidmuller were real, in spite of objections to the method used be- 

 cause of the possibility of hydrogen or methane evolution. 



Zweibaum (1921) studied the rate of Oo consumption of Paramecium 

 caudatum in relation to conjugation. He found that the rate just before 

 conjugation was about 0.73 mm' O2 per thousand organisms per hour. 

 During conjugation this rate rose to 3.4 mm'/l,000/hour, and immedi- 

 ately after conjugation decreased to about 0.73. During the first eight 

 or nine days following conjugation, the rate rose slowly to 2.0 

 mm'/l,000/hour, and remained at this value from four to five months. 



