INTRODUCTION 



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A B C D E F G 

 METHOD 



Fig. 5. Percentage distribution of methods 

 employed in studies of invertebrate tissue re- 

 spiration from 1929 through 1959. Methods indi- 

 cated are: A. Manometric (Warburg, Hj 

 specified.^ ). B. Differential (Barcroft, 

 ; Thunberg,^3 ; unspecified, 



Fenn, 



un 



). 



C. Microvolumetric. D. Chemical (Winkler and 

 micro-Winkler). E. Spectrophotometric . F. Po- 

 larographic. G. Miscellaneous. 



2 per cent with the polarograph (fig. 5F), and 3 

 per cent with a variety of miscellaneous proce- 

 dures (fig. 5G). 



The selection of method as a function of year 

 is illustrated in figure 6. That the Warburg 

 method has been a perennial favorite is clear 

 from figure 6A. In only eight out of the 30 years 

 has there been no use of the Warburg method 

 for studies of invertebrate tissue respiration; 

 furthermore, in every year since 1945 this 

 method has been used at least once. During the 

 1950's the Warburg method was selected for use 

 on the average of four times a year. 



With the advent of spectrophotometric methods 

 for the investigation of tissue metabolism, vari- 

 ous investigators applied these procedures to 

 invertebrate tissues, most frequently those of 

 insects. Particular mention may be made of a 

 study by Shappirio and Williams (1957a, 1957b). 

 Through spectroscopy at low temperatures (see 

 Keilin and Hartree, 1949), Shappirio and Williams 

 (1957a) were able to detect enzymes of the term- 

 inal electron transport system in diapausing 

 pupae of the Cecropia moth, even though these 

 enzymes are present during this stage of the life 

 cycle in extremely low concentrations. Subse- 

 quently (1958b), by the spectrophotometric 

 method, they traced changes in the activity of 

 these enzymes during diapause and adult devel- 

 opment (see Discussion, p. 82). 



Studies involving the use of differential respir- 

 ometers, including the Barcroft, Fenn, and 

 Thunberg, have appeared quite regularly through- 

 out the 30-year period (fig. 6B), without, appar- 

 ently, marked fluctuations in the frequency of 

 their use. A scarcity of studies employing mi- 

 crovolumetric techniques (fig. 6C) seems some- 

 what surprising in view of the convenience of 

 this t3^e of procedure. 



