Jan. 13,1923 
New Respirometer for Seeds 
109 
These respirometers are adapted for use with small material which 
does not have to be studied under aquatic conditions, provided it is not 
markedly sensitive to reduction in the partial pressure of oxygen or to 
increase in that of C 0 2 . Some seeds, however, are so small as to pass 
through the i-mm. holes of the seed container. For use with such 
material, the perforations can be partially closed with paraffine. The 
change in the total pressure of all gases is always small. The manipu¬ 
lations and observations can be performed rapidly and the admittedly 
somewhat tedious computations may be delayed to suit one’s convenience. 
The apparatuses could probably be adapted for use with aquatic 
organisms, at least in certain cases, by substituting an appropriate 
container for the perforated seed container. They are probably not 
sufficiently sensitive for use in such work, as, for instance, that of Lund 
(75) with Paramecia, where the total differences in C 0 2 production to 
be measured are sometimes such as would correspond to less than i-cm. 
change in pressure as registered on the manometer of the smallest of the 
apparatuses here described, or about ten time the possible experimental 
error. In sensitiveness and therefore in the character of work for which 
they are adapted, they are intermediate between the apparatuses used 
for large objects and those of the micro type. 
Plate 1 is a photograph of the carrier with two respirometers and a 
thermometer in place. To facilitate the reading of the manometers, 
which will almost invariably show some reduction in pressure, the res¬ 
pirometers were so constructed that their manometers are turned to the 
left when the stopcocks in the caustic chambers face outward or away 
from the tall central post. 
The usefulness of the apparatus, as here described, can be greatly 
extended by attaching to the bottom of the respiration tube a side arm 
with stopcock for use in the introduction of artificial atmospheres. For 
work with artificial atmospheres it is desirable also to omit the short 
delivery tube (fig. 1, M) below the caustic chamber in order to facilitate the 
complete sweeping out of the original atmosphere. We have a few of 
the apparatuses in this modified form and have used them with good 
results, although they embody also some of the less desirable features of 
our earlier attempts. 
The apparatus obviously can not be used except at approximately 
atmospheric pressure, though the proportions and nature of the gases 
present can be altered. For the study of respiration at greatly reduced 
or increased total pressures other forms of apparatus must be used. It 
will always be true, however, that the great bulk of the work on respi¬ 
ration will be done at atmospheric pressure. 
FORMULAE FOR CALCULATION OF THE RESULTS OF RESPIRATION 
EXPERIMENTS 
The following formulae can conveniently be used : 
1. For the reduction of volumes to o° C. and 760-mm. mercury 
pressure. 
/ 273 P Y 
V760 (2734-2)/ 
(1) voi. ; 60 =voi. 1 x 
in which t and P represent the temperature of the bath in degrees centi¬ 
grade and the pressure of the gas in millimeters of mercury. The 
