OXYGEN RESPIRATION 49 



the removal of the portion v. The desired total volume x of 

 gas in the flask is calculated from these data on the basis of 

 the law of Boyle-Mariotte: 



_ vH 

 "" ~ h - h' 

 Then xh = xh + vH. 



If the volumes of the oxygen absorbed and the carbon dioxide 

 liberated are known, the amounts by weight of both gases are 

 obtained by simple calculation. 



If very large amounts of plants are being used for investiga- 

 tion, or if it is impossible to introduce the research material 

 into the neck of the flask without damaging it, the flask is 

 replaced by a bell jar, the upper opening of which is closed with 

 a two-hole rubber stopper. Into the holes of the stopper are 

 introduced the same tubes as were referred to in the preceding 

 description of the Kostychev flasks. The lower rim of the bell 

 jar must be fitted to a ground glass plate by means of vacuum 

 grease. For accurate experiments the bell jar together with 

 the glass plate is placed in a crystallising dish of mercury in 

 order to obtain an entirely faultless seal. The rubber stopper 

 at the upper opening of the bell jar is also immersed in mercury. 

 In this way the manipulation of the bell jar is entirely analogous 

 to that of the flask. The research material is placed in a dish 

 on the glass plate and then covered with the bell jar. 



Orchnary eudiometer tubes may be used to advantage for 

 very small amounts of research material. The material is 

 introduced into the upper part of the eudiometer and held in 

 position with glass wool. The lower end of the eudiometer is 

 then immersed in mercury and the operation proceeds according 

 to the general principles of gas analysis methods.'" 



"■ The reader must realize that many of the most important methods for the 

 study of respiration have not been mentioned by Kostychev. The present 

 tendency appears to be toward the use of physical rather than chemical methods 

 of following the changes in concentrations of the oxygen, carbon dioxide or 

 both. The following are representative and most easily adapted to a variety of 

 material and the various types of problems which arise. 



B. D. Bolas has recently presented the details and results of a comparative 

 study of three "methods for the study of assimilation and respiration in closed 

 systems" (New Phyt. 25: 127-144. 1926). The Haldane gasometric method 

 4 



