THE PROGRAMME 11 



almost always in that strange plight in which the physicist 

 would be if he always had to go to volcanoes in order to 

 study the conductivity of heat, or if he had to wait for 

 thunderstorms in order to study electricity. The biologist 

 is dependent on the specificity of living objects as they occur 

 in nature. 



A few instances may show you what great incon- 

 veniences may hence arise to impede practical biological 

 research. We later on shall have to deal with experiments 

 on very young embryos : parts of the germ will have to be 

 destroyed in order to study what will happen with the rest. 

 Now almost all germs are surrounded by a membrane ; this 

 membrane has to be detached before any operation is 

 possible. But what are we to do if it is not possible to 

 remove the membrane without killing the embryo ? Or what 

 if, as for instance in many marine animals, the membrane 

 may be removed but the germs are killed by contact with 

 sea-water ? In both cases no experiments at all will be 

 possible on a sort of germ which otherwise, for some special 

 circumstances of its organisation, might have given results 

 of importance. These results become impossible for only a 

 practical, for a very secondary reason ; but enough : they 

 are impossible, and they might have thrown light on 

 problems which now must remain problems. Quite the 

 same thing may occur in experiments on physiology proper 

 or functional physiology : one kind of animals survives the 

 operation, the other kind does not, and therefore, for merely 

 extrinsic reasons, the investigations have to be restricted to 

 the first, though the second might have given more im- 

 portant results. And thus the biological experimenter 

 always finds himself in a sort of dependence on his subjects, 



