SECT. 2] AND WEIGHT 537 



the same effect as all three together though the a radiation was 

 100 times as much as the other two. Forsterling obtained retardation 

 of growth in rabbit embryos by irradiating the mother, and other work 

 on mammals was done by Cohn, by Lengfellner, and by Bagg, but the 

 conditions are there so complicated that it is not worth discussing. 



The effect of electricity upon embryonic growth has been fairly 

 often tried, but usually in an unintelligent way. Eggs have simply 

 been placed between the electrodes or between the poles of a magnet, 

 and conclusions have been drawn which would probably not bear 

 statistical examination for a moment. Thus Rusconi in 1840 stated 

 that frog's eggs hatched more quickly under the influence of electric 

 currents than otherwise. Lombardini remarked the same effect in 

 amphibian development but noted a large number of abnormalities, 

 as did Fasola. Windle, working with eggs of the trout, found no 

 acceleration of development either under the influence of electric 

 currents or of a large magnet, but he noticed that the hatched trout 

 died very quickly. Rossi found many anomalies in the eggs of urodele 

 amphibia subjected to electric currents, but no other effect. Slater 

 did not find any result at all when he subjected silkworm eggs to a 

 strong magnetic field, nor did Maggiorani when he subjected hen's 

 eggs to one. Finally, Benedicenti found no effect of constant weak 

 currents on the development of echinoderm eggs. The more recent 

 work includes that of Scheminzki on the trout — he could observe no 

 acceleration of development when the eggs were subjected to con- 

 stant sub-lethal currents, but the membrane at the end of the 

 development was weaker than usual so that the embryos tended 

 to hatch early. Gianferrari & Pugno-Vanoni passed currents of 

 9000 volts at 450,000 periods/second through suspensions of trout 

 {Salmo lacustris) and echinoderm {Echinus esculentus) eggs, but the 

 effects observed were merely teratogenic, and the abnormalities pro- 

 duced did not differ, apparently, from those produced in other ways. 



The subject still awaits an investigator who will sweep up all this 

 debris into some coherent theory of the action of electrical currents 

 and magnetic fields on embryonic development. 



The other factors, such as osmotic pressure, which have been 

 shown to affect growth so greatly in the post-natal stages and in 

 plants, do not exercise so much influence on the foetus, guarded as 

 it usually is from the world around it by the egg-shell or the uterus. 

 Their effects have therefore not been much studied in the case of 



