96 FOURTH REPORT 1834. 



possible to abstract many of the conditions without destroying 

 life, innumerable modifications of the experiment can alone afford 

 an approximation to certainty. It is to experiments, in the hands 

 of able men, whei'e the condition may be suppressed without de- 

 stroying life, that we owe a knowledge of various portions of the 

 nervous system which is no longer problematical*. 



But we are not to expect too much frol^l experiment. It may 

 jjoint out the variety and the extent of vital reactions, but can 

 teach us (as Miiller has pointed out,) nothing of the nature or 

 fundamental cause of these. For here the experiment is not like 

 one in chemistry, where, the known agent which excites reaction 

 in another unknown, entering as an element into the effect pro- 

 duced and ascertained, we are able to infer from what is known of 

 the nature of the one element that which was before unknown of 

 the nature of the other. But although we are thus necessarily re- 

 stricted to observation of the sequences of the phaenomena, and 

 of the conditions under which they occur and are modified, yet we 

 cannot suppose that they are without some fundamental cause, 

 however it may be hidden from us. " Falso asseritur sensum 

 humanum esse mensuram rerum ; quin contra omnes percep- 

 tiones, tam senses, quam mentis, sunt ex analogic, hominis, non 

 ex analogia universit." 



When physiological facts have been accumulated by observa- 

 tion, extended through all living things, it is the object of the sci- 

 ence to determine the general relations which subsist amongst 

 them ; to ascertain what is common to these relations ; and thus, 

 ascending constantly to more comprehensive generalizations, to 

 arrive at that cause, least limited by conditions, which holds in- 

 ferior causes in subordination. And this is all that any experi- 

 mental science can pretend to. 



On the contrary, however, the first philosophy of nature was 

 almost entirely deductive. The authors of it persuaded, as ra- 

 tional creatures, that all parts of the creation are but portions of 

 an harmonious whole — productions of the same intelligent first 

 cause — were led to speculate on the nature of that cause, and 

 thence deduced systems from assumed principles. The universal 

 appeared to express itself hi particulars. It became the object of 

 philosophy to begin with the essence of things, and from it to de- 

 rive and explain all their phaenomena. Such a philosophy, deal- 

 ing with abstractions, with primary essences of which the quali- 

 ties and their relations were necessarilyhypothetical, could scarce- 

 ly have any application to a particular creation — to the world as it 



• Miiller, Introductory Essay to his Vergleichende Physiologie des Gesicht- 

 sinnes. 



t Novum Orgarmm, 41. 



