PATHOLOGICAL STATES IN EVOLUTION. 



239 



ease is it more likely to occur than in that of the biologist, who, 

 by the very name and nature of his task, should include in his 

 apparatus a considerable knowledge of everything which deals 

 with the organic, and even inorganic, world. Science, however, 

 is kept in more or less water-tight compartments, and it seems 

 left to the mathematician to hold the opinion that his own 

 branch of learning has, somehow or another, deep relations with 

 all things, including life itself. Even by him it does not seem 

 to have been pointed out that in things living and non-living 

 certain principles of construction rule alike. However much 

 they were wedded to mechanico-physical explanations, biologists 

 have assuredly often ignored the fact that any organism is con- 

 struction, and knowing little of the laws of construction have 

 ignored basal facts familiar to every architect or even every 

 artisan. It was reserved for Wolff, in formulating his law of 

 bone-growth and reaction to stress, to propound a principle more 

 far-reaching than he recognized, when he showed that living 

 bone, reacting to normal or abnormal stimulation, can be proved 

 to develop in accordance with the principles of engineering and 

 architecture. 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 proportional 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 profound 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 develop- 

 ments result not from the happ}'--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 pro- 

 found importance. If this principle proves sound, it is obvious 

 that immense labour has been spent by biologists 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 bra.nch 

 of physiology. On the other hand, many pli3 r siologists and patho- 

 logists have done good work in some branches of evolutionary 

 theory. Bland-Sutton, in his fruitful little book 'Evolution and 

 Disease/ pointed out that "Pathology is only a department of 

 Biology, and it is important to bear this in mind in studying 

 disease." It is true that he went little further than to show that 



