AN INDICATOR METHOD OF MEASURING THE 

 CONSUMPTION OF OXYGEN. 



By W. J. V. OSTERHOUT. 



{From the Labor atory of Plant Physiology, Harvard University, Cambridge) 

 (Received for publication, September 11, 1918.) 



The study of respiration has been greatly facilitated by using indi- 

 cators to measure the production of carbon dioxide. It is desirable 

 to employ similar methods for estimating the amount of oxygen con- 

 sumed in respiration. With this in view the writer has investigated 

 a number of substances, some of which appear to give promising re- 

 sults. The purpose of the present note is to describe very briefly 

 the use of Limulus blood for this purpose. 



The blood of Limulus (and of a number of other invertebrates) 

 when shaken up with air absorbs oxygen and turns blue, but on stand- 

 ing is reduced and in consequence becomes decolorized. It has been 

 pointed out by Alsberg^ and by Harvey^ that the decolorization is due 

 (in large part at least) to the activity of microorganisms. It seemed 

 to the writer that this might be utilized to measure the rate of con- 

 sumption of oxygen in respiration. 



The procedure adopted is as follows: Large horseshoe crabs are 

 taken and an incision' is made at the joint in the middle of the body; 

 the body is then repeatedly bent back and forth to expel the blood. 

 After the blood has stood for a short time a clot forms from which 

 the clear blue serum may be poured off. To a portion of this sufl&- 

 cient ether is added to form a saturated solution; this is allowed to 

 stand in a stoppered bottle with occasional gentle shaking, until the 

 ether is dissolved. A number of glass tubes are prepared by sealing 



^ Alsberg, C. L., /. Biol. Chem., 1915, xxiii, 495. Alsberg, C. L., and Clark, 

 E. D., ibid., 1910-11, viii, 1. Alsberg, C. L., and Clark, W. M.,ibid., 1914, xix, 

 503. Alsberg, ibid., 77. 



2 Harvey, E. N., /. Gen. Physiol., 1918, i, 133. 



^ This enters the heart cavity. It is desirable to cleanse and dry the surface 

 around the joint before making the incision. 



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