APPENDIX B 



The Pe rone us Tf.rtius 



IT seems as if the peroneus tertius, a muscle only 

 found in the human organism as a special portion 

 of the mechanism for preserving the structure of the 

 foot from damage in orthogrades, is a key case for the 

 opponents of transmission. This muscle is a lesser 

 opponent of the tibialis anticus, which is found well 

 developed in simians not using, or only rarely using, 

 the upright posture. It must, then, have come into 

 existence at a late period of evolution. This is em- 

 phasized by the fact, that a few fibres of the tertius are 

 occasionally found in the gorilla. Is such a direct 

 adaptation to be attributed to germinal variations, that 

 is to say, to accident, if we hold that the germ- 

 plasm does not respond magically to new needs ? To me 

 this seems much more than unlikely. A new muscle 

 has arisen at a special point of strain as a part of the 

 set of muscles preserving the arch of the foot and, 

 as we see from pathology, it is not yet doing its work 

 with complete success. It is still imperfect. If such 

 a muscle is not a direct adaptation to new stresses 

 words have ceased to have any meaning. To say that 

 a single muscle cell or fibre arose from a "spontaneous " 

 germinal variation, and was found advantageous, is to 

 make a mockery of mechanism. But if it is assumed 



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