EXPERIMENTS ON ASCIDIANS 43 



3. The objection might now be raised that the 

 bladder and rectum are minor organs of the body. 

 But what has been said above concerning them 

 also holds good for larger and more important 

 groups of organs, namely for the blood-vessels. 

 These are able to adapt their width to external con- 

 ditions ; the vessels of the skin become dilated when 

 a loss of heat is desirable, and they contract in the 

 cold when the loss of heat should be reduced. It is 

 assumed that the mechanisms for these purposeful 

 reflexes are contained in the central nervous system. 

 Goltz and Ewald (4) have found, however, that dogs 

 which have lost the spinal cord almost up to the me- 

 dulla oblongata live for years. This alone proves 

 that the blood-vessels can adapt themselves to the 

 external temperature, independently of the central 

 nervous system. Goltz had already proved that the 



blood-vessels regain their tonus if all the nerves of a 

 & 



limb be severed, the limb being connected with the 

 animal only by means of the blood-vessels. The 

 same thing occurs after extirpation of the spinal cord. 

 The temperature of the hind-paws of animals whose 

 spinal cord has been destroyed up to the thoracic 

 part becomes normal again after the operation that 

 is to say, the hind-paws have the same temperature 

 as the fore-paws which remain connected with the 

 central nervous system. If we hold the hand in 

 snow for a time, we observe as a local after-effect a 

 relaxation of the muscles of the blood-vessels and an 

 increase in the temperature of the hand. Goltz and 



