ELRMENTAKY PIIOIJLKMS IN IMl VSlOLCXn.* 



r>v Prof. ,). S. IUtkdox Sa.ndkwson. 



TIjp work of invcstigatiiii; tlu' si)o('ial fiuictioiis of oi-^ans, wbicli 

 (luriiift' the hist two decades lias yiehled sncli splendid results, is still 

 ])roceeding, and every year new .urouiid is being broken and new and 

 frnitt'nl lines of experimental incjuiiy are being opened up; but the fur- 

 ther the physiologist advances in this work of analysis and differentia- 

 tion, the more frequently does he iind his attention arrested by deeper 

 (piestions relating to the essential endowments of living matter of which 

 even the most highly differentiated functions of the animal or plant 

 organism are the outcome. In our science the order of progress lias 

 been hitherto and will continue to be the reverse of the order of nature. 

 Nature begins with the elementary and ends with the complex (first the 

 auKvba, then the man). Our niode of investigation has to begin at 

 the end. And this not merely for the historical reason that the tirst 

 stimulus to physiological inquiry was man's reasonable desire to know 

 liimself, but because the differentiation actually involves simplilication. 



l^hysiology therefore first studies man and the higher animals, and 

 }>roceeds to the higher plants, then to invertebrates and (;ryi)toganis, 

 ending where development begins. - - - 



It is not difficult to see whither tins method must eventually lead us. 

 For inasmuch as function is more ctnnplicated than stiucture, the 

 result of proceeding, as j)hysiology normally does, fiom structure to 

 function, must inevitably be to bring us face to face with functional 

 <]ifterences which have no structural difference to explaim them. Thus, 

 for example, if the i^hysiologist undertakes to explain the function of 

 a highly differentiated organ like the eye, he tinds that up to a certain 

 l)oint, provided that he has the requisite knowledge of dioptrics, the 

 method of correlation guides him straight to his i)oint. fie can men- 

 tally or actually construct an eye which will perform the functions of 

 the real eye, in so far as the formation of a real image of the tield of 

 vision on the retina is concerned, and will be able thereby to under 

 stand how the retinal picture is transferred to the organ of concious- 



*Presitlential address bel'oio the Biological Section f)f tin; lUitisli Association, A. S., 

 at Newcastle, September, 1889. (Report of Ike Jiriiiuli J.s.sor/V///'o«, ^^>!. i.ix, ])p. (i04- 

 614.) 



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