72^ PHYSIOLOGY IN RELATION TO 



or gemmation ; through two different series of metamorphdtic 

 changes. And such a phaenomenon as the production of a par- 

 ticular tissue may depend — in the case of adipose tissue, for 

 example — upon the employment in Nature's laboratory of one or 

 the other of two different chemical compounds. Pain may be, as 

 Dr. Handfield Jones has shown paralysis is, produced in one case 

 by the impact of shock upon nerve-centres, in another by the cur- 

 tailment of their supply of blood. In each and all of these cases, 

 the maxim which has many a time been sonorously enunciated in 

 these Schools, 'Entia non sunt multiplicanda praeter necessitatem,' 

 would, if listened to, have closed our ears and eyes to at least one- 

 half of the truth. That Bacon would have classed this maxim 

 with his ' Idola Theatri,' I think I am justified in saying, for that 

 in the very next section (Section xlv) of the 'Novum Organon' to 

 that in which he treats of these delusive notions, I find these 

 words : — ' Intellectus humanus ex proprietate sua facile supponit 

 majorem ordinem et aequalitatem in rebus quam invenit;' and if 

 I am told, as by Mr. Mill (' Logic,' vol. ii. p. 379, ed. 1846), that 

 Bacon, in the actual practice of investigation, acted as though 

 there were no such thing as Plurality of Causes, I need only 

 answer that herein his practice did not differ from his precepts at 

 all more widely than does the practice of many other writers, of 

 many practising, of many teaching doctors, differ from theirs. I 

 have a satisfaction in quoting the living De Candolle, who enjoys 

 one of the first and best deserved scientific reputations of the day, 

 in repudiation of Maupertuis' famous principle of Meast action.' 

 De Candolle writes thus in his ' Geographic Botanique,' vol. ii. p. 

 li^: ' Nous aimons k croire aux moyens simples, peut-etre unique- 

 ment a cause du peu de port^e de notre esprit.^ 

 , "What, then, is the legitimate application? where does Nature 

 really bind herself to the observance of a ' Law of Parsimony ' ? 

 In, as I thinkj three distinct lines of her operations. 



Where an organ can be diverted from one and set to discharge 

 another function, there Nature will spare herself the expense of 

 forming a new organ, and will adapt the old one to a new use. 

 She is prodigal in the variety of her adaptations, she is niggard in 

 the invention of new structures (Milne-Edwards, cit. in Darwin's 

 * Origin of Species,' p. 232). The complicated arrangement of co- 

 operating muscles whereby the bird's third eyelid is drawn across 



