THE BUILDING OF REFLEX ARCS 251 



We are told on high authority that not education but educa- 

 bility is transmissible, and yet this humble reflex appears in very 

 young dogs that could hardly if ever have known the impact of a 

 stone. Incidentally we are compelled to remember how in past 

 battles of our youth the aim both of " ourselves and the enemy " 

 was deplorably poor, and not from want of practice. This school- 

 boy-stone reflex is either an example of educational effects trans- 

 mitted or of a minute bit of the unpacking of an original complexity 

 which it would require the brain of a de Quincey to work out. But 

 if we suppose the initial stages of such a stimulus as the occasional 

 impact of a stone in many generations to be slowly ingrained in the 

 skin -receptors, reflex-arcs and receptors We do not need opium 

 either for the acceptance of orthodox dogma or to aid us in the 

 Mendelian alternative to a very simple ideal construction. 



This digression bears on the initiative of the more important 

 scratch -reflex, and it is profitable to ask " are not both of these 

 reflexes in dogs examples of Evolution of the Indifferent ? " Is it 

 possible to imagine that from its inception to its fully -formed state, 

 with a specialised territory of skin -receptors accurately mapped out, 

 with receptor neurones, reflex-arcs and adapted effectors, this 

 scratch -reflex can have arisen through Germinal Selection or 

 selective processes within the germ ? At no stage can anything 

 more than a contribution to more or less comfort to the animal be 

 held to xesult from its operation. It is strangely reminiscent of the 

 proceedings of an elderly man after lunch on a hot day when he 

 protects his head against house-flies with a handkerchief. I am 

 aware that it is but one of a large number of reflexes produced for 

 the purpose of grooming the trunk head or limbs of animals as low 

 down in the scale as the house-fly or grasshopper, many of which 

 were beautifully described a few years ago by Miss Frances Pitt 

 in the National Review in an article dealing with small mammals, 

 chiefly rodents. But I have availed myself here as elsewhere, of 

 the liberty of doing what Professor Sherrington says we may do, 

 and consider this scratch -reflex as split off from the rest of the 

 animal's behaviour for the purpose of analysis. He also says in 

 discussing the subject of parasites moving across the receptive 

 surface of the skin that the ulterior purpose may be the removal 

 of what " would confuse its function as a receptive surface to more 

 significant environmental stimuli." This statement is hypothetical 

 and the problem obscure ; but at any rate we know this that the 

 removal of the parasite must conduce to the greater comfort of the 

 dog without any more recondite purpose. The one suggested by 

 Professor Sherrington would in some possible but very vague 



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