A METHOD OF STUDYING RESPIRATION. 



By W. J. V. OSTERHOUT. 



{From the Laboratory of Plant Physiology, Harvard University, Cambridge) 

 CReceived for publication, July 2, 1918.) 



In 1915 the writer suggested to Dr. Haas the desirabihty of experi- 

 ments with indicators with a view to measuring the amount of CO2 

 given off by organisms. The method finally developed by Dr. Haas^ 

 in the writer's laboratory consists in adding the indicator directly 

 to the liquid in which the organism is placed. The indicator is 

 usually present at the start, but in some instances it is not added until 

 after the CO2 has been produced. 



The method is simple, accurate, and extremely satisfactory but it 

 has obvious limitations. It is restricted to the use of aquatic organ- 

 isms and furthermore it does not permit us to study the effect upon 

 respiration of reagents which have a pronounced acid or alkaline reac- 

 tion. There are also difficulties in using organisms or tissues which 

 give off alkah or acid (other than CO2). In addition, the use of small 

 suspended organisms which color the solution must be avoided. 

 A further disadvantage is that some reagents cause organisms to give 

 off coloring matters which interfere with the results. The use of toxic 

 indicators also presents difficulties. 



These difficulties may be obviated by means of an apparatus 

 designed by the writer. The purpose of the present article is to make 

 clear the principle employed and to describe a simple form of the 

 apparatus without mentioning other forms or discussing the modifi- 

 cations of mechanical details which are of importance for special 

 purposes. 



The apparatus shown in Fig. 1 consists of a bottle. A, in which 

 the organisms are placed; the CO2 which they exhale passes out of A 

 through D into the indicator solution^ in the Pyrex glass tube, B,^ 



1 Haas, A. R. C, Science, 1916, xliv, 105. 



^ The tube which dips into the indicator solution should be of Pyrex glass. 

 This glass is chosen because the amount of alkali given off is negligible. 



^ This tube should be about f inch in diameter; the stopper should be covered 

 with a parafifin which does not give off acid. 



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