REPORT ON ANIMAL PHYSIOLOGY. 97 



actually exists, however rigidly its conclusions might be de- 

 duced. 



A different procedure was forced upon physicians : their very of- 

 fice constrainedthem to observe the same vital phaenomenon under 

 different circumstances, — to compare different phaenomena, — to 

 separate what was common and essential from that which vyas 

 merely contingent and partial. Thus was established a new prin- 

 ciple of explanation, a principle little agreeing, perhaps, with 

 that deduced in the former way. As observation and experiment 

 extended the boundaries of this inductive knowledge of causes, it 

 continually encroached more and more upon the limits of hypo- 

 thetical belief. And the principles which were thus established, 

 being founded in realities, were really the expression of the phae- 

 nomena from which they were derived. It has been, however, by 

 slow and gradual steps that men have become wilUng to abstain 

 from assuming, as a privilege of the understanding, the power of 

 creating that spontaneously which can only be supplied by the long 

 and patient contemplation of nature. The two systems have been, 

 more or less, in conflict from the earliest to the present times. 



Hippocrates was the first, whose writings have come down to 

 us, who made experience the interpreter of nature. He collected 

 a rich treasure of observations, the accumulated result of his own 

 labours and of those of his family during 300 years. They relate 

 to the investigation of the effect of changes in the external con- 

 ditions of life, — viz. air, warmth, moisture, food, — upon its phae- 

 nomena in man. On the other hand, his ideas of matter were 

 founded on the speculations of the Pythagorean school. He taught 

 that the four elements, variously combined, produced the four 

 cardinal humours, and these again the different organs of the body. 

 A vital principle, or principle of motion, i^va-is, or ivofiLmv, was. 

 superadded, depending upon innate heat, its manifestations 

 being excited by external things, &c. We see not how the theory 

 has its application. Though Hippocrates did not, with many of 

 the ancients, suppose that the vital phaenomena may be explained 

 by the properties of matter alone, but referred them to a prin- 

 ciple of life acting under external conditions ; yet his assumed; 

 properties of living matter are nowhere verified, nor the altera-, 

 tions asserted to be produced in such properties by alterations in. 

 the conditions of life in any way established. 



Aristotle far excelled his predecessors in extending natural sci- 

 ence by observation, and may be considered as the founder of com- 

 parative anatomy and zoology. His anatomical descriptions of 

 the elephant and the whale have merited the eulogy of Camper., 

 Those portions of his works in which he records his observations 

 of the mental faculties of animals, and compares them with those 



1834. H 



