Modification of Embryo 325 



Guyer's Experiments 



The most impressive experiments in this field have been 

 carried on in this country by Professor Michael F. Guyer 

 of the University of Wisconsin and his associates. These 

 consisted essentially of an attempt to influence the develop- 

 ment of rabbits within the womb of the mother by intro- 

 ducing into the pregnant mother's blood specific substances 

 calculated to affect a specific part of the organism. The 

 most definite and the most consistent results were obtained 

 by injecting a special serum made from the blood of hens 

 that had been previously sensitized to the lens of rabbits' 

 eyes. We have seen (page 61) that the introduction of a 

 foreign protein will bring about in the blood of animals 

 certain changes that bear a specific chemical relationship to 

 these foreign substances. Guyer injected a pulp made from 

 the eye-lens of rabbits into the blood of hens. He thus 

 obtained a serum that had specific properties which showed 

 themselves in actually dissolving eye-lens substance. 



Now the introduction of this serum containing the anti- 

 lens substance into the blood of pregnant rabbits sometimes 

 proved fatal and sometimes caused injury to the adult rabbit; 

 but never produced any effect upon the eyes. Moreover, these 

 injections did not affect the eggs, since normal rabbits were 

 subsequently bred from females thus treated. When, how- 

 ever, the injection was made into rabbits pregnant from ten 

 to fourteen days (the period during which the embryo eyes 

 are developing) definite results appeared. Of the surviving 

 baby rabbits, of which there were sixty-one, four had one or 

 both eyes clearly defective, and five others had more or less 

 serious abnormalities of the eyes. Among the hundreds of 

 offspring of other rabbits, similarly treated with ordinary 

 fowl serum (that is, from fowls not specially prepared) and 

 with other special serums, not one ever showed such eye de- 

 fects; and none of the treated mothers showed such eye de- 

 fects. Whatever the serum did, it acted apparently upon the 

 embryo rabbits while still in the wombs of their mothers. 



