NO. I IRRADIATED ASCARID OVA WRIGHT AND IVIcALISTER 5 



embryonated. In each of these instances it is apparent that the ultra- 

 violet light prevented development in a relatively large proportion of 

 the Toxascaris eggs. In other cases the differences in embryonation 

 were well within the limits of experimental error in the counting 

 technic. 



SERIES B 



In view of the fact that wave lengths from 2652 to 2967 A are below 

 the limits of the solar spectrum, there appeared to be little information 

 of practical value to be derived from the further irradiation of ascarid 

 eggs at these wave lengths even though Toxascaris ova were consider- 

 ably affected by irradiation at wave lengths of 2652 and 2804 A. For 

 this reason further experiments were confined to irradiation of the ova 

 at wave lengths within the range of the solar spectrum with a view to 

 ascertaining the relative lethal effect of sunlight, exclusive of heat and 

 desiccation, on the ova of these two species of ascarids. This point has 

 practical application in the control of ascariasis. 



In series B the ova were exposed to a dosage approximately equal to 

 40 times that used in series A. The dose was equivalent to 27,400,000 

 ergs/cm\ This exposure for dish i (wave length 3022 A) was ap- 

 proximately equivalent to 12 hours of noonday, midsummer sun at 

 Washington, D. C. 



For this test, a mixed culture of Toxocara and Toxascaris ova was 

 dried in the bottom of 50-mm culture dishes for 10 minutes. After the 

 eggs had dried on the bottom of the culture dish, water was added to 

 the dish to a depth of 2 mm. This prevented drying of the culture 

 during the period of irradiation. An area equivalent to the light aper- 

 ture, or 5 by 30 mm, was marked off on the bottom of each culture 

 dish with a diamond point and the eggs within that area were exposed 

 to the ultraviolet light. Eggs without this area were not exposed and 

 were used as controls. After exposure of the eggs, formalin was added 

 to the culture dishes to provide a concentration of i per cent in order 

 to prevent bacterial growth in the cultures. Temperatures during de- 

 velopment of the cultures ranged between 29° and 30° C. Counts were 

 made nine days after irradiation ; 200 ova were taken in each count. 

 The results of the experiment are recorded in table 2. 



In only one case was there any apparent toxic effect from the ultra- 

 violet irradiation in series B. In dish i (wave length 3022 A) there 

 resulted a marked lethal effect on the ova of both Toxocara canis and 

 Toxascaris icouiua, although the eft'ect was most marked on the ova of 

 the latter species. Of the ova exposed at this wave length, 24.5 per 

 cent of the irradiated Toxocara eggs developed to embryonation, where- 



