Maech 29, 1907*] 



SCIENCE 



491 



which the situation might require of it. It 

 is a wonderful, prompt, adaptive motor 

 mechanism with a good reserve of force. 



We have, then, in the circulatory system 

 many instances of provisions with factors 

 of safety to assure nutrition of all parts 

 of the body in all states and conditions. 

 An abundance of blood, a superabundance 

 of blood vessels, a vast provision of factors 

 for the safety of the adaptation of the 

 two to one another and a great reserve of 

 motor force for transportation and distri- 

 bution of the blood. 



The multiple mechanisms existing for 

 the care of the vasomotor apparatus lead 

 us to the following considerations. The in- 

 ternal motor organs of the body like the 

 gastrointestinal canal, the heart, the uterus, 

 etc., are provided with central motor in- 

 nervations as well as with local motor 

 mechanisms. In all cases it has been 

 shown that the movements of the organs 

 continue also after the severance of the 

 connections with the central nervous sys- 

 tem. Thus the heart continues beating 

 after section of both vagus and accelerator 

 nerves, the peristalsis of stomach and in- 

 testines continues after cutting the vagi 

 and the splanchnics, and pregnancy and 

 delivery take a normal course after com- 

 plete destruction of the spinal cord. On 

 the basis of these facts it is now generally 

 assumed that the extrinsic innervations of 

 these organs have only a regulating func- 

 tion, while the real motor function is in- 

 vested in peripheral devices, be they of 

 neurogenic or of myogenic character. This 

 conclusion is obviously based on the sup- 

 position that the function of an organ is 

 carried on only by a single mechanism. 

 Hence the fact that the motor work is 

 carried on after eliminating the extrinsic 

 nerves seems to be sufficient evidence that 

 they can not form an integral part of the 

 motor function. 



These conclusions are fallacious. There 



is an abundance of instances in which one 

 and the same function is cared for by 

 more than one mechanism. But we need 

 only refer to the vasomotor apparatus. It 

 was known before and it has been very 

 recently conclusively demonstrated again 

 by Magnus that, after eliminating the in- 

 fluences of the sympathetic and the central 

 nervous system, the blood pressure is well 

 taken care of by the peripheral mechanism 

 of the walls of the blood-vessels. Never- 

 theless, nobody doubts that the vasomotor 

 centers are integral parts of the vasomotor 

 mechanism. "Why this difference of views 

 for the different organs of the body? 



The subject is evidently an important 

 one; but we shall not enter into a further 

 discussion of it. The remarks were made 

 to illustrate the importance of the concep- 

 tion that in the animal body one function 

 is not infrequently cared for by more than 

 one mechanism. It is capable of pro- 

 foundly affecting the views on many vital 

 biological problems. 



We shall cite a few more instances in 

 which two or more parallel mechanisms 

 exist for the accomplishment of one func- 

 tion. I may be permitted to mention in 

 the first place the function of deglutition. 

 As was shown by us about twenty-five 

 years ago, fluids and semifluids are squirted 

 down from the mouth to the cardia by the 

 force of the contraction of the mylohyoid 

 muscles, but they can also be carried down 

 by the peristalsis of the oesophagus. Of 

 the latter there are again, as I have re- 

 cently shown, two kinds: a primary per- 

 istalsis which runs independently of the. 

 integrity of the oesophagus and a secondary 

 peristalsis which is closely connected with 

 the integrity of the tube and which is more 

 resistant to certain detrimental influences. 

 It will probably be shown before long that 

 the oesophageal wall alone is also capable 

 of contributing to the function of carry- 

 ing the food down to the stomach. 



