A System for Microspectrophotometry Employing a Commercial Recording Spectrophotometer

The present paper describes the design and performance of an attachment for the Cary model 14 recording spectrophotometer, which permits the accurate recording of absorption spectra in small areas. A special compartment built into the light path of the spectrophotometer holds a low-magnification microscope (“macroscope”) consisting of two opposed quartz condensers, with which measurements can be made between 300 and 700 mμ in fields 0.1 to 1 mm in diameter. This can be replaced by a conventional microscope with which spectra can be measured from about 350–650 mμ in fields as small as 4 μ in diameter. These arrangements have been used to measure the absorption spectra of visual pigments in situ. With the macroscope, such measurements have been made in small areas of surviving retinas; and with the microscope, they have been made in single isolated outer segments of rods. The present paper contains examples of each type of measurement.