142 A. RICHARDS AND A. E. WOODWARD. 



In all the experiments with sperm it has been our policy to use 

 only data from clear cut reactions in which the beginning and the 

 end of the agglutination were definitely marked. Precautions 

 were taken to see that the sperm suspension was fresh and clean. 

 Lillie has shown that both of these factors are important, for an 

 old suspension becomes inactive and the presence of impurities 

 such as blood acts as an inhibitor of the reaction. 



Previous experience (Richards, 14) has shown the radiations 

 to be of three kinds in relation to their effect on enzymes depending 

 on duration, intensity and distance of the object from the x-ray 

 tube; namely, accelerative, non-effective, and inhibitive. Under 

 the conditions which usually prevailed in these experiments, a 

 short exposure, of about 2 minutes, is accelerative; an exposure 

 of about five minutes is non-effective ; and one of longer duration 

 becomes inhibitive. In view of these facts, similar exposures of 

 fertilizin were made and the resulting activity tested as already 

 explained. 



In a preliminary experiment on July 8 the following figures were 

 obtained as the average of a number of readings of the time 

 elapsing before the complete reversal of the agglutination reaction 

 after short and long radiation of fertilizin. The fertilizin solution 

 used was about 2 per cent, standard strength (in this early ex- 

 periment the strength was not accurately determined, but it is 

 not strictly necessary under the conditions of this test that it 

 should be known exactly). For the control, non-radiated solu- 

 tion the average reaction time was 32 seconds; for the 2-minute 

 radiation the average time was 33 seconds; and for the 15-minute 

 minute radiation it was 23^ seconds. This solution was then 

 diluted to one-half and these figures obtained : Control, 19 seconds; 

 2-min. radiation, 20 seconds; 15-min. radiation, 16 seconds. 

 This experiment is incomplete and the differences lie nearly within 

 the limits of variation, but they suggest definitely that the short 

 radiation rendered the fertilizin slightly more active (that is, 

 enabled it to hold the sperm in agglutination longer), and the 

 long radiation caused it to be less active than the control. More 

 decisive data would have been given had the dilutions been 

 continued to unit concentration, a fact which led to the adoption 

 of that method in subsequent experiments. 



