180 The Unity of the Organism 



So much in illustration of the service of the two end di- 

 visions of the autonomic nervous system. 



What, exactly, we now inquire, is the nature of the service 

 performed by the thoracico-lumbar division? Since this 

 part is, as already seen, antagonistic in its action to both 

 the cranial and sacral parts wherever it innerv^ates an organ 

 or part also innerA-ated by these end-parts, the inference is 

 readily drawn that its service to the organism as a whole 

 would also be in a sense opposed to the services of the 

 cranial and sacral divisions. Only a moment's reflection 

 is necessary to recognize that at some points at least this 

 is so. For instance, quickening of the heart beat through 

 innervation by the thoracic autonomic nerves, thereby send- 

 ing the blood stream more rapidly and strongly through the 

 whole body, is clearly opposed, so far as these acts in them- 

 selves are concerned, to the slowing of the heart and hence 

 of the blood stream by the vagus nei'A^e, i.e., by. cranial au- 

 tonomic innervation. Now this can mean nothing else than 

 that whereas the vagal (cranial) autonomic action is in 

 the interest of upbuilding and conserving the organism in 

 its whole normal, wonted life, the speeded-up action through 

 the thoracic autonomic is in the interest of some special, 

 more or less temporary need or condition. But obvious and 

 important as is this opposition between the two subdivisions 

 as concerns heart innervation, of not less importance, though 

 less easily observable in their full scope, are the oppositions 

 and reciprocations brought about in the peripheral blood 

 vessels of the whole body through the innerv^ation of the 

 muscles of the arterial walls by the thoracico-lumbar au- 

 tonomic in connection with the heart action. These in- 

 nervations, coupled with those of the smooth muscles of the 

 gastro-intestinal canal, of the sweat and probably other 

 peripheral glands, of the smooth muscles of the hairs in 

 mammals, of the adrenal medulla for the secretion of 

 adrenin, and of the liver for releasing stored carbohydrates 



