Receptors, Neurons, and Effectors 121 



always the contraction of striped muscle. Thus, on this assumption, all 

 forms of consciousness are concomitants of reflexes. 



The important question now is : what sort of reflexes condition con- 

 sciousness ? The answer is : those which take place through the ' central 

 nervous system' (brain and cord). The reflexes through local ganglia 

 (such as the ganglia in the walls of the alimentary canal, or in the heart), 

 may be omitted from consideration, as probably having no part in the 

 conditioning of consciousness. 



It is commonly supposed that only the reflexes which take place through 

 the cortex are ' conscious '. In fact, it is often held that it is the action of 

 cortical cells which is the ultimate condition of the consciousness. For 

 this view there seems to be no strong evidence. For aught we know action 

 of muscle may be the more essential part of the process, and it is safest 

 for the present to make no attempt at localization within the total reaction 

 process. We cannot even admit that it is essential for the production of 

 consciousness that the arc (or path) of the reflex should lead through the 

 cortex. A spinal reflex has all the essential conditions of consciousness, 

 so far as we know. It would be rashly dogmatic even to say positively 

 that the reflexes within the intestinal plexuses of Auerbach and Meissner 

 do not condition consciousness, although we admit that this is possible. 



In order to avoid confusion, the reader must here note that the term 

 reflex is here used in the strict technical sense to designate the total process 

 taking place over an arc; that is, the process beginning in an end-organ 

 (such as the cone in the retina), passing along a series of neurons (arc) 

 to the spinal cord, and in some cases from thence to the brain, and finally 

 reaching some effector (muscle or gland cell), or effectors, whose activity 

 is consequently modified. This process is called a ' reflex ' because it may 

 be thought of (in an untechnical way) as a process which is directed in- 

 ward to the nerve center, and from hence reflected out again to the 

 periphery. 



Unfortunately the process in which a reflex terminates, which is properly 

 called re flex -action, has come to be described by many writers by the 

 shorter name ' reflex '. This is bad usage. The mere contraction of the 

 iris, for example, when light is suddenly thrown into the eye, is a ' reflex 

 contraction ' but is not a ' reflex '. The ' reflex ' is the total process begin- 

 ning with the retinal activity produced by the light stimulus and terminat- 

 ing in the pupillary contraction. 



Another source of confusion lies in the fact that formerly it was assumed 

 that only a limited class of activities are the results of reflexes. ' Reflex 

 action ' was set over against ' voluntary action ', and sometimes other forms 

 of action were distinguished from these. The more modern view, which is 



