PREVIOUS INVESTIGATIONS UPON ANIMALS 47 



The first recorded attempt I have found to ascertain the inde- 

 pendent effect of the different kinds of radium rays was made by 

 A. Exner^^ in 1904. He separated the ^ from the y rays by means of 

 the magnet, and found that they both produced the same kind of 

 result on the tails of mice, but the /9 rays were less active than the y 

 rays. In the same year Gillman and Baetjer^^ found that the eggs 

 of Amblystoma^ exposed to X rays, developed faster than normally 

 for a few days, though eventually their development was markedly 

 altered and checked. These authors announce that similar results 

 were obtained by Bardeen with the hen's egg. 



When invertin, emulsin, and trypsin were exposed to the radia- 

 tions from radium, Henri and Mayer ^^ found that their activity gradu- 

 ally diminished and was finally entirely lost after several days 

 exposure. 



Perthes*^'** found that eggs of Ascaris megalocephala, exposed 

 in drop cultures to radium and to Rontgen rays, had their first division 

 delayed, and their further development made irregular and slower 

 than normally. Eggs in the resting or in the dividing condition 

 served equally well for the experiments. Centrosomes and spindle 

 fibers were unaffected, but in Ascaris megaloce^hala univalens the 

 characteristic number of chromosomes was doubled. In the course 

 of the chromatin loops there appeared knotty swellings instead of the 

 normal, club-shaped enlargements. In a few eggs, instead of the 

 usual two chromosomes on the equatorial plate, there were observed 

 numerous, unequal pieces, though Perthes suggests that this may 

 have resulted from the mode of sectioning, and says, " I cannot con- 

 sider that a disintegration of the chromosomes by Rontgen rays has 

 been demonstrated." The eggs exposed to X rays" gave rise to ab- 

 normally developed worms. 



Phisalix*^ exposed the venom of a viper for periods of 6, 20, and 

 58 hours to radium rays. Its toxicity was decreased by the shorter 

 exposures and finally destroyed by the longer. By means of radium 

 rays Tizzoni and Bongiovanni^'^^ and Novi*^" obtained an attenuated 

 virus of rabies {in vitd). The length of exposure necessary to render 

 the virus inoffensive varied with the organ in which the injection was 

 made. JVassula and Trypanosoma Brucei, studied by Salomonson 

 and Dryer,*'' were killed in from two to three hours by rays from ra- 

 dium, and cyst-forming amoebae were injured. The contractile 

 vacuoles of ciliates were distended, and their period of contraction 



