MUSCLES 211 



where I saw the process continually going on, I hazarded the 

 generalisation that any species, annually reproduced from seed, 

 could be broken down in five years. During that period specific 

 stability, though menaced, tends to maintain itself. Darwin 

 was well aware of this." 1 



Most biologists from time to time betray the fact that their 

 minds can only be relieved from an intolerable burden, in accounting 

 for the numberless adaptations in organisms, by the view that 

 many of them originate through factors of use and stimuli from 

 environment, and at first are entirely indifferent as regards the 

 survival or better mating of their possessors. To which the stern 

 opponent replies " What is there to show that in the existing scheme 

 of things there is any provision made which will minister relief to 

 the burden of your little mind ? " To which, " answer came there 

 none," except a subdued reflection that everything we see of living, 

 striving nature around us has a most provoking way of speaking to 

 us of daily, hourly and incessant action and reaction, stimulus 

 and response, and that those who view the process thus do seem 

 to bring some order into what would otherwise be chaos — and 

 yet all the while someone is being grossly deceived ! This " may 

 be magnificent but it is not proof," some will say, and will ask if 

 the older observers of the heavenly bodies were not wrong in their 

 complete conviction that the sun went round the earth. This 

 digression introduces the role of the fly-shaker. If I am told 

 that this muscular sheet in a cow or horse to-day is a relic of raw 

 material inherited from a remote ungulate stock little evolved, 

 and that it contributes in hot weather in the time of flies to the 

 comfort and better mental state of the cow or horse, that it shall 

 be able to keep those enemies at bay, and that the muscle is kept 

 well in order by two or three months' practice in each year I can 

 understand in a measure its presence to-day. It has an efficient 

 ally in the sweeping tail of a cow and that of a wild horse, and both 

 of these weapons are further aided by the mobile ears of cow and 

 horse, and the stretching movements of its head and neck. Thus 

 the body of a cow, for example, is like a map with four territories 

 delimited, that of the fly-shaker, the tail, the ears and the head and 

 neck. Between these offensive weapons a cow is better defended 

 against flies than a European in India by his punkah, or China 

 was by its great wall, or Britain by the wall of Vallum of Hadrian 

 or the wall of Severn s, which with forts and garrisons was designed 

 to protect it. Speaking in allegory the evolving brain of an early 



1 Nature, November 28th, 1907, p. 78. 



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