ROLLESTOX ON COBBELATIOWS OF QBOWTE |s."» 



our constitutional craving after rationales, has called into use, if not 

 into being, the several theories of adherence to type, of complemen- 

 tal nutrition, of genealogical, yet modified, transmission, and of cor- 

 relation of growth. 



The first of these theories has won with us not a little popularity; 

 its antique dress, striking the eye, diverted the attention from tie 

 utter incongruity which exists between Platonic mysticism and 

 modern science ; and, appealing to our reverence for the dreams of 



our youth, it has lived longer, and made more converts than unas- 

 sisted by the associations of the Academy it ever could have done. 

 Even now it is fairly in the way of developing out of the larva stage 

 of an Idolon Theatri into an Idolon Fori, a more active, elusive, albeit 

 fragile, Imago. But a few years back, the joint empire of final and 

 formal causes, of confederated ideological and morphological consi- 

 derations, seemed firmly established in a country delighting in com- 

 promise ; the legitimacy of the one, and the prescriptive right of the 

 other, placed them, when united, in an apparently unassailable posi- 

 tion. The appearance of the theory of complemental nutrition in a 

 deservedly well-known work* caused men to accept of a triumvirate 

 of ruling causes. Material causes counted for something as well as 

 final and formal ; "Wolff's theory could suffice not only for the ration- 

 alization of many phenomena which Paley and Oken did explain, but 

 also for the elucidation of some with which their philosophies were 

 incompetent to deal. Mr. Paget's exemplifications of the law of 

 complemental nutrition seem drawn exclusively from a class of cases 

 of what I would call " heterogeneous growth." The evolution of the 

 one structure has rendered possible the evolution of the other, by 

 setting free some residual product which Nature in her economy has 

 worked up into such secondary structure. The perfecting of the 

 plumage contemporaneously w r ith the perfecting of the sexual func- 

 tions in the pairing bird is one, and may serve as a type of all, of the 

 instances given by Mr. Paget. There is no equality in rank between 

 the two structures, which stand to each other in this relation of 

 complemental nutrition ; the one is supported by what the other finds 

 useless, superfluous, or even hurtful; after the production of the one 

 the organism aims and labours, the other is but a " nebenprodukt ;" 

 they are heterogeneous in the same sense as the food of the hound 

 and the food of his master, and often in a yet truer sense still. 



The instances of Correlated Growths to which I am about to 

 refer, and which from the dissection I shall detail, I hope to eluci- 

 date, differ from those classed under the head of Complemental 

 Nutrition, in that both growths draw with equal right, and toanequal 

 extent, upon the same store of nutriment. To the same stock of 

 alimentary matters they stand in the same relation ; they share and 

 share alike either as joint consumers or joint elaboratore of it. If 

 we may coin a word from but second-hand Greek, and borrow one-half 



* Paget Lectures on Surgical Pathology, Vol. !, Lecture ii. 



