354 ANNUAL EEPOBT SMITHSONIAN INSTITUTION, 193 3 



treatment with ultraviolet rays diminished the virulence of the or- 

 ganism but increased the antigenic power. This work suggests a 

 method for building up an immunity by successive injections of 

 organisms irradiated for regularly diminishing periods of time. 

 Evidence has been found that a few strains, or perhaps a single 

 strain of bacteria may be sufficient for immunization against a 

 heterogeneous group of types. 



Bacteria and their products when sensitized previously are more 

 easily affected by irradiation. Passow found that the staphylococ- 

 cus bacteria were more quickly killed by the yellow-green rays, and 

 in a longer time by the blue and violet rays if they were sensitized 

 with rose bengal before irradiation. In general, the dyes with sensi- 

 tizing properties stained the bacteria better than those which did not 

 possess these properties, and with the exception of toluene red and 

 indigo carmine, all the dyes which stained the staphylococci well 

 and were not toxic were sensitizers. In the treatment of bacterial 

 eye diseases, Passow recommends rose bengal as an aid to photo- 

 therapy, since it helps render the long rays with deep action bacteri- 

 cidal as well as the short rays which in themselves possess bactericidal 

 qualities (Laurens, 1933). 



Bo vie and Dalland (1923) found that ultraviolet made specimens 

 of Para^noeciwri caadatum extremely sensitive to heat, so that sub- 

 lethal temperatures killed them. Heat following irradiation caused 

 a greater degree of injury than heat preceding irradiation. If the 

 temperature remamed constant, the degree of sensitization varied 

 directly with the temperature. 



Diseases of plants that ali'ect agricultural economics can also be 

 treated with ultraviolet irradiation. Mulvania (1926), Newell and 

 Arthur (1929), and Duggar and Hollaender (1934) have inactivated 

 the virus of typical tobacco mosaic by ultraviolet irradiation, thereby 

 ofleanine: information of value to farmers and horticulturists. The 

 spores of grain smuts can be killed by the short rays, as shown by 

 the work of Pilcher and Wober (1922). The fungicidal action of 

 the short wave lengths has also been proved by Fulton (1929) with 

 a number of fungi, many of which cause harmful diseases of plants. 



A contribution that promises to be of great value to humanity is 

 now in progress at the Cancer Research Laboratory at the Univer- 

 sity of Pennsylvania. By means of microphotography and micro- 

 moving pictures, Allen, Franklin, and McDonald (1933) show the 

 effect of ultraviolet rays on living organisms, such as Protozoa and 

 the correlation of the effects with the absorption. The microscope 

 used has an all-quartz optical system originally designed to make use 

 of the higher resolving power obtained by using short ultraviolet 

 wave lengths to which the glass systems are opaque. The micro- 



