Abstract
The present paper deals with the diminution of the virus activity with increasing time of the ultraviolet irradiation.
Supernatant (3, 500 rpm for 15 min.) of the infected pupal blood was diluted 10-3 or 10-3 with distilled water and centrifuged at 3, 500 rpm for 10 minutes. The fluid was prepared in a Petri dish at the depth of 2-3 mm, being exposed to ultraviolet radiation from Matsuda GL-15 type ultraviolet lamp with about 95 per cent of its ultraviolet output at a wave length of Å and tape distance from the lamp to Petri dish was 40 cm. The sample was gently agitated every 5 minutes. After the ultraviolet irradiation, decimal dilution was performed immediately and 0. 005 ml of the virus solution was injected into pupae. LD50 was calculated after REED and MUENCH.
Results obtained are shown in Fig. 1. There is a linear relationship^between LD50 and the irradiation period accords with the mode of the inactivation of other viruses, and when the higher diluted virus solution is used, the inclination of the line becomes steeper. Silkworm jaundice virus seems to be inactivated by the absorption of one ultraviolet quantum as in the inactivation of bacterial virus.
The temperature in these experiments was 15-20°C and its increase owing to the irradiation was less than 2°C after 60 minutes.
