NATURAL HISTORY OF ORGANIZED BODIES. 281 



SO long contended for mastery come to ns from the same som'ce. Aristotle, avIio 

 encimihered science with entities nselessl}' imagined, has bequeathed to lis many 

 exact ideas on the nature, whether voluntary t)r involuntary, of movement, on 

 the development of the foetus, &c. Erasistratus, who represented vital spirits as 

 circulating in the arteries, recognized the true nature of the action of the nuiscles. 

 Galen, so much prepossessed with humorism, with the four elements, with the 

 forces which preside over the functions, was not the less a great experimentalist. 

 He alone made more discoveries than all his predecessors ; he showed that it is 

 with blood that the arteries and the heart are tilled ; he pointed out the influence 

 of the nerves on the movement of the nmscles ; he recognized the paralysis pro- 

 duced by a lesion of the spinal marrow. He realized, in fine, one of the most 

 striking experiments of physiology, by showing that the section of the recurrent 

 nerves paralj^zes the larynx and extinguishes the voice. 



Soon afterwards all progress is arrested before the invasion of the barl)arians, 

 and science remains torpid for 14 centuries. On its revival, the two parties reap- 

 pear more opposed than ever ; A\ith an antagonism more precisely defined, and 

 each boasting its proper representatives. While Stahl revives the immaterial 

 principles of Plato, Hoffman vindicates the supremacy of physical laws in the 

 phenomena of life. Establishing themselves on the grand discovery of Harvey, 

 the organicians proceed to demonstrate the potency of the experimental method. 

 Finally, Haller api)ears, and, reasseml)ling the materials of physiology, mahes of 

 it a well-defined science, and impels it onward in the path of experiment. 



Since this epoch discoveries have rapidly succeeded one another ; witli each 

 of them the name (»f some experimentalist is associated : J. Hunter, Bichat, Ma- 

 gendie, Ch. Bell, J. Miiller, savants Avliose work has been so abty continued ])y 

 our cotemporaries. Animal physiologv has reached a very advanced stage, and 

 one of great interest. Having emerged from that unsatisfactory phase in which 

 the sciences, while in a state of formation, are engaged in accumulating isolated 

 facts, and too often in seeking to connect those facts by premature hypothesis, avo 

 are able not only to realize the principal conditions under Avhich certain functions 

 are performed, but to obtain a view of their relations and reciprocal influences. 

 In the collective functions of the organism, we discover, in effect, a subordination 

 such as Cuvier has pointed out in the organs themselves. The nervous systeuj, 

 the most constant apparatus in animals, presides over sensibility and movement, 

 the two prominent functions in the animal economy. But it governs also the 

 functions of organic life — respiration and circulation, which in turn react upon 

 the nervous system, so that the knowledge of one function would not be complete 

 if we did not know at the same time its influence upon the others. 



Vegetable physiology is unfortunately much less advanced ; it can scarcely bo 

 said to consist of more than certain rather vague ideas. Not only is it true that 

 we do not at present understand the general harmony of the functions of plants ; 

 we have but a very incomplete knowledge of each of those functions in itself. 

 T\\Q pjhyiologists have attempted to model themselves upon the procedure of the 

 zoologists, but without deriving much benefit from the imitation. 



Tlie functions of the vegetable have been classed nearly in conformity with 

 the functions of the animal, but this assimilation may itself have operated as a 

 shackle on the progress of the science. All that has been said of the circulation 

 in plants was plainly suggested by ideas borrowed from the circulation in ani- 

 mals. The double current of liquid supposed to ascend by the tubes of the lig- 

 num and to descend again by those of the latex, would seem, according to modern 

 authors, but a false analogy established between the physiology of animals and 

 that of plants. Vegetable respiration is however better known. The experi- 

 ments of Bonnet, Priestley, Senebier, and Th. de Saussm-e have established the 

 important fact, that the green parts of vegetables exhale oxygen under the influ- 

 ence of solar radiation, while, in darkness, these same parts disengage carbonic 

 acid. 



