276 APPENDIX B 



that continual stress can produce such a muscle reaction 

 we may infer that continued strain would reinforce it. 

 We can, in fact, prophesy that in time such continued 

 stresses will secure adequate response. We must also 

 infer that, when a set of muscles is used in a new position, 

 as was the case when the upright posture was adopted, 

 opposing muscles are no longer properly counterbalanced. 

 Some new muscle is called for. It is obvious that such 

 new strain must be repeated in embryo if the muscle 

 is to increase, since new muscles fibres do not come into 

 existence later. As the embryonic tibialis anticus begins 

 to exert a pull, these stresses are felt by yet undifferenti- 

 ated cells, the parents of muscle cells, which are capable 

 of becoming muscle if so stressed. Without such em- 

 bryonic strains the tissues would have altered in some 

 other manner. If language is not to be tortured into 

 something which serves no function, we must come to 

 the conclusion that new stresses are repeated during 

 development, and exert a morphogenetic influence upon 

 the undifferentiated tissues. If this is so transmission is 

 no longer guesswork. 



