REPAIR IN EVOLUTION 65 



or abnormal stimulation, can be proved to develop in 

 accordance with the principles of engineering and archi- 

 tecture, although he apparently laid far too little stress 

 on the action of muscle in bone transformation. This 

 law may, I feel assured, be extended to every living tissue, 

 and in such an extension will be found the key to many 

 phenomena still awaiting explanation. 



To one who holds this view, the work lately done by 

 Starling on the Law of the Heart, which shows that the 

 force with which the heart contracts is directly propor- 

 tional to the length of the muscular fibres at the end of 

 the preceding diastole, is by no means surprising. It 

 is indeed on a par with the conclusions of Wolff as regards 

 bone, and might, I believe, have been deduced from it or 

 from the form I suggest, provided it is understood that each 

 varying tissue has its own acquired typical reaction. 



If, then, it can be shown that disease has had a pro- 

 found effect upon the evolution of all organisms, and 

 that analogous results are found in every kind of human 

 constructive effort in such numbers as to suggest as a law 

 that all great variational developments result, not from 

 the happy-go-lucky aggregation of small advantageous 

 variation, or from discontinuous variation, whether of a 

 Mendelian character or not, but rather from partial failure 

 and repair, we seem to be in sight of a general principle of 

 profound importance. If this principle proves sound, it 

 is obvious that immense labour has been spent by biolo- 

 gists endeavouring to explain life without seeking help 

 from other workers. Though they may show some general 

 knowledge of the cell, and even special knowledge of the 

 reproductive cells, I find few who appear to have studied 

 general embryology, to speak only of one branch of physio- 

 logy. On the other hand, many physiologists and 

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