MICROSPECTROSCOPE 



51 



one or other of the various reactions making up the whole system. The re-oxidation 

 of cytochrome is inhibited by cyanide, carbon monoxide, azide, etc., all of which 

 combine with the cytochrome iron. It is noteworthy that the inhibition by carbon 

 monoxide is reversed by exposure to Ught. The dehydrogenase system is inhibited 

 by narcotics. 



It should be noted that oxidation of some substrates in the presence of cytochrome 

 requires not only dehydrogenase but also coenzyme I or II. 



The identity of cytochrome oxidase is the subject of some discussion. It has 

 been found to be identical with the indophenol oxidase present in many cells, which 

 catalyses the oxidative coupling of a-naphthol and p-phenylene diamine (the " Nadi " 

 reagent) yielding indophenol blue. Warburg's iron-containing respiratory pigment or 

 Atmungsferment has a similar distribution and absorption spectrum and it is now 

 commonly thought to be identical with one of the cytochrome components (a 3). 



Largely on the basis of differences in absorption spectra cytochrome has been 

 •diiferentiated into a number of components (ai, ag, b, c, etc.). 



Fig. 14 

 A new observation cell for the micro-spectroscopic examination of bacteria, etc. 



It may be mentioned incidentally that in order to overcome the difficulties 

 associated with the spectroscopic examination of pathogenic bacteria, the simple 

 apparatus shown in fig. 14 was devised by the author and has proved very effective. 

 The apparatus is used with the ordinary microspectroscope (which is mounted, in place 

 of the eye-piece, on a microscope). The device is made in two parts, the observation 

 cell and an attachment to the microscope objective. The observation cell is mounted 

 on a miscroscope slide and consists of an inner chamber to contain the suspension 

 of organisms and an outer annular space to hold mercury and provide an air-tight 

 seal, with the double advantage of preventing both evaporation and accidental 

 scattering of organisms during the manipulation. The cell is constructed of two short 

 lengths of glass tubing of internal diameter 8 mm. and 18 mm. respectively. One 

 end of each of the tubes is ground flat and sealed to the slide with Canada balsam. 

 This easily renewable method of sealing is of great advantage since the apparatus 

 can be sterilised in boiling water after use, and then can be re-assembled readily, 

 rapidly and cheaply. The other part of the apparatus is attached to the microscope 

 objective by means of a rubber bung, the upper half of which is bored to fit over 

 the objective. The lower half of the bung is bored to take a glass rod 5-5 mm. 



