Data obtained on yeast irradiated with monochromatic ultra-violet radiation has been analyzed for the number of quantum hits involved in the production of different degrees of inhibition of cell division, according to the method proposed by Mme. Curie (1929). Sufficient data are not available for a rigorous determination, but the calculated results tend to indicate that a multiple hit to kill r...

The uptake of protoporphyrin IX by Propionibacterium acnes in suspension has been studied by fluorescence spectroscopy. Protoporphyrin, after it was injected into a cell suspension, was firstly bound to receptors on the cell surface and in this state protoporphyrin was non-fluorescent. Subsequently, probably as a result of lateral diffusion in the cell wall, these protoporphyrin-receptor comple...

In the preparation of the material and the interpretation of the results, I have had the cooperation of Dr. Mary B. Stark of the Flower Hospital Staff and the assistance of Miss A. K. Marshall of the Bell Telephone Laboratories. The photographs which accompany this paper are sufficiently described in the titles and need not be specifically dealt with here. 1 Lucas, "An Introduction to Ultra-Vio...

Determination of the absorption spectra of pure preparations of Northrop's crystalline pepsin inactivated by irradiation with ultra-violet light shows that the total absorption in the ultra-violet region of the spectrum increases with the degree of inactivation. This increase is especially marked between 2400 and 2750 A.u. The rate of photoinactivation is shown to be sensitive to changes in pH,...

In this paper I have chosen some diseases and conditions which can be greatly benefited by the use of ultra-violet light. In writing these notes I have dealt with each subject from three points of view, viz : (1) the rationale of the use of the ultra-violet rays; (2) the available authoritative literature on the subject; and (3) the technique in detail. The following ten conditions will now be ...

The specimens Diptera: Musca dornestica and Ludlia sp. adapted to dark were offered two monochromatic lights of different wavelengths. Musca dornestica always preferred the light of a shorter wave out of two monochromatic equiquantum lights. Six color regions presumably qualitatively different were distinguished for this fly: violet-blue, blue, green, yellow-green, orange and red. Lucilia sp. e...