Cesium in the Mammalian Retina. ∗

Fox and Ramage 1 and Sheldon and Ramage 2 reported that they were unable to identify, by spectrographic methods, cesium in the tissues of animals of widely divergent genera. Since it is well recognized that different methods of spectra excitation favor the identification of some elements it occurred to us that by use of the interrupted are method (McMillen and Scott 3 ) we might get the identifying lines. Fox and Ramage and Sheldon and Ramage used flame excited spectra in their studies. An examination of several hundred tissue and fluid samples from various mammals by our method failed to give any positive results.

Through the kindness of Dr. Douglas Coles of The Veterinary Research Laboratories, Onderstepoort, Transvaal, South Africa, we obtained several ox eyes. In the course of routine spectrographic analysis of these specimens for barium, cesium was found in the retina. This led us to study spectrographically the retinae of some 60 eyes obtained from a local abattoir. Of this group 19 were from pigs, 17 from oxen and 24 were from sheep. Presumably the animals came from a rather wide though illy defined area of the Middle West. No more definite information could be obtained on this point.

By carefully controlling the method used it was possible for us to exclude contamination from other sources. The eyes were slit and fixed in cesium-free formaldehyde as it was found much easier to separate the retinal layers in the hardened material. The instruments used in manipulating the tissue did not add cesium to samples of other tissues and consequently it is not at all likely that they did so in this case. The tissues to be examined were allowed to digest in a small amount of cesium-free HNO₃ in chemically clean vessels.