NERVOUS SYSTEM AND JIERKDITY 205 



be no doubt that the connection between the morpho- 

 genetic functions and the central nervous system is 

 much more slight than between this organ and the 

 sensory and motor functions. 



I am inclined to believe that the simultaneous dis- 

 appearance of gills and tail-fins is due to some change 

 occurring in the blood, e.g., the appearance of certain 

 enzymes, or possibly changes in the number of red 

 blood corpuscles, etc. 



It has been urged that in this experiment the sympa- 

 thetic system transmitted the connection between the 

 two halves of the animal. The sympathetic has 

 always been used as a bridge across the gulf between 

 preconceived notions and facts. I am pretty certain 

 that at least in a number of my Amblystomas the sym- 

 pathetic was cut. But as I did not make sure of this 

 I will not urge this point. But I may at least point 

 out the true reliability of this bridge. It had been a 

 generally accepted belief that the secretory activity 

 of the milk glands during and after pregnancy was 

 caused by the stimulation of the nerve-endings of the 

 uterus. Goltz severed the spinal cord in the pectoral 

 region of a female dog which afterwards became preg- 

 nant and gave birth to young ones. It turned out 

 that the mammary glands in front and behind the place 

 of the section began to secrete milk equally well. 

 Goltz concluded that the secretion was not due to a 

 nervous influence. As was to be expected, those who 

 try to explain everything by the omnipotence of the 

 central nervous system at once pointed out that the 



