EFFECT OF X-RADIATION ON FERTILIZIN. 



143 



In another experiment (July 14) a 1/50 dilution (2 per cent, 

 standard) of Arbacia fertilizin was used. It was separated into 

 four parts, of which one (Sc) was kept as a control solution, one 

 (S2) was radiated 2 minutes, one (S5) five minutes, and the last 

 (S7) seven and a half minutes. The results of these solutions 

 when tested for their agglutination time at successive dilutions 

 to unit concentration are given in the following table. >^Sc 

 means control solution diluted to one-half; ^ Sc, diluted to one- 

 fourth, etc. The difference between two successive reaction times 

 is marked d. Unit concentration is indicated by the asterisk (*). 



Table I. 



Inspection of this table shows that the activity of S2 was 

 increased by the short radiation, for five dilutions were required 

 to reduce it to unit concentration, whereas that state was reached 

 in four dilutions in the other three solutions ; also the full strength 

 of this solution held the sperm in agglutination longer than did 

 that of the control, 37 against 34 seconds. In other words, Sc 

 was 800 units agglutinating strength, S2 was 1,600 units, S5 and 

 S7 were each a little over 800 units, and much below i ,600 units 

 strength. (Lillie, '14, p. 527.) 



The number of dilutions required in S5 was the same as in Sc 

 and the sperm were agglutinated the same time by both solutions. 

 This is in line with the previous experience that a radiation of 

 about five minutes' duration under the conditions of these experi- 

 ments is non-effective. However, these figures give an additional 

 fact of possible significance which has not been entirely confirmed 

 by other experiments either on fertilizin or on enzymes such as 

 pepsin. If d represents the differences between the number of 

 seconds required for the reversal of the reaction by successive 

 dilutions, its value in S5 is practically a constant, 7 ; but in Sc and 



