78 A CHEMICAL SIGN OF LIFE 



these nerves are present in the body region, and they 

 are wholly sensory without admixture of motor fibers. 

 The fibers of both nerves are dendrites of ganglion 

 cells which lie in the head. 



When these fibers were subjected to our tests it was 

 found that in every case the proximal portion of the 

 fresh nerve gave much less carbon dioxide than the distal 

 portion, indicating that the gradient is correlated with 

 function and not with development. And in this case 

 it should be noted that, although the fibers of both nerves 

 are dendrites of their respective neurons and conduct 

 afferent impulses, the function of the two nerves is 

 widely different, the lateral line nerve (ramus lateralis 

 vagi) being excited by water vibration and the accessory 

 lateral line nerve (ramus lateralis accessorius) being 

 exclusively gustatory in function. The quantitative 

 estimates on these nerves given in Table XII will illus- 

 trate the presence of this marked gradient of carbon 

 dioxide of the sensory dendrites. 



TABLE XII 



CARBON DIOXIDE PRODUCTION FROM DIFFERENT PORTIONS 



OF LATERAL LINE NERVE (RAMUS LATERALIS 



VAGI) OF CARP 



That the metabolic gradient is directly associated 

 with the functional direction is strikingly shown also by 

 further studies with different fibers in which quantitative 

 determinations were not made, but in which the output 



