206 COMPARATIVE PHYSIOLOGY OF THE BRAIN 



sympathetic connected the two halves of the spinal 

 cord in Goltz's dog. Recently Ribbert made an ex- 

 periment which, if correct, does away with these 

 mysterious sympathetic influences (8). He trans- 

 planted a milk gland to the ear of a guinea-pig. The 

 guinea-pig became pregnant and the gland on the ear 

 began to secrete. It is evident that a change in the 

 blood or lymph must be responsible for the secretion 

 of milk glands during pregnancy, possibly the appear- 

 ance of certain enzymes. 



Schaper has added an experiment that speaks for 

 the lack of dependence of the morphogenetic devel- 

 opment on the central nervous system. In a tadpole 

 six mm. long he extirpated the brain and the medulla 

 oblongata. When the animal was killed seven days 

 later, the spinal cord seemed to have vanished. 

 Nevertheless the healing of the wound, growth, and 

 development continued during the seven days (2). 

 In face of the fact that the first processes of de- 

 velopment precede the formation of the central ner- 

 vous system in every animal, these results need not 

 surprise us. They suffice, however, to convince us 

 that the processes of development and the formation 

 of organs are less closely connected with the central 

 nervous system than the sensory and motor processes. 

 For this reason we cannot well decide in favour of the 

 assumption that every impression on the central nerv- 

 ous system must impart itself to the egg, with which 

 it is, moreover, not connected. 



3. But how shall we make the fact that certain 



