implanted in matter and the forces of matter ; and that these laws 

 have gradually but necessarily at every stage been operative on the 

 plastic organisation, adapting it continuously to the new conditions 

 which it was ever encountering ; in default of which adaptation and 

 renovation of the disturbed harmony, the organisation itself could 

 not have survived. The laws must be studied in the^ phenomena ; 

 and he particularly discusses and illustrates the operation of three 

 laws, which for shortness' sake he calls those of habit, of exercise, of 

 inheritance. But it is not enough, he adds, to deduce the necessity 

 of the harmony from these laws ; we must endeavour to fathom these 

 laws themselves more deeply. The two former, those of habit and 

 of exercise, mutually interacting, continually tend towards a restora- 

 tion of the harmony between the organism as a whole and its sur- 

 roundings, and between the several component parts of the same 

 organism, as the harmony becomes by little and little disturbed in 

 lapse of time by the intercurrence of altered conditions. The last 

 law, that of inheritance, carries over into the future the accumulated 

 modifications of the past, so far as they have survived in the latest 

 offspring, thus preserving the continuity of life through successive 

 generations, but only by essential changes in its forms. " Already 

 some light dawns in science on the causes of the phenomena we 

 referred to, the laws of habit and of exercise ; and thus, ascending 

 from cause to cause, without ever losing ourselves in dreams about 

 the purpose, we approach, slowly it is true, but with firm step, the 

 ideal point of view, according to which all the phenomena of nature 

 will be seen proceeding from the attributes of the elements and 

 elementary forces. And if once by an All-wise Omnipotence these 

 elements and forces have been created for a predetermined purpose, 

 and if the conditions of the whole future have been enshrined in 

 their attributes, then also not a single drop of blood flows without 

 purpose through our veins, but it is a purpose which lies outside the 

 science of nature." 



As Donders had originally approached physiology from the side of 

 medicine, so now he had evidently come to meditate deeply on this 

 great theme of the procession of organic forms down the tracts of 

 time on independent grounds of his own, and rather as a physiologist 

 than as a naturalist. As other matters were engrossing his attention, 

 he did not pursue this one to further conclusions ; but he welcomed 

 with delight the publication, in 1859, of Charles Darwin's book, ' The 

 Origin of Species ;' became, subsequently, the friend and correspond- 

 ent of its illustrious author ; and visited him at Down. He also, some 

 years later, undertook, at his request, more than one elaborate inves- 

 tigation,* designed to elucidate obscure questions relating chiefly to 



* E.g., " On the Action of the Eyelids in Determination of Blood from Expi- 

 ratory Effort," by F. C. Dondere, translated in Scale's ' Archives,' 1870. See also 



