NATURAL HISTORY OF ORGANIZED BODIES. 285 



the diapliragm or walls of the breast of an animal, alive or dead, were pierced; 

 there is now nothini^ obscure in the nature of this effect. The same cause 

 explains also many phenomena relating to the exchange incessantly produced 

 between the gases of the Idodd and the atmospheric air, the action of respiration 

 on tiie course of the blood, &c. Mechanics elucidates the muscular phenomena, 

 and in general all the movements produced by animals. The circulation of the 

 blood borrows from hydrodynamics the explanation of everything relating to the 

 movement of the sanguineous fluid. Without chemistry, what ideas could wc 

 possess respecting the digestive functions, the offices of respiration, the function 

 of the glands? Optics and acoustics are treated, in the works on physiology, in 

 the same manner as in those on physics. Finally, the laws of electricity acquire 

 every day more 'mportance in the interpretation of the nervous phenomena. 



All this proves the reciprocal dependence {solidarifi/) of the sciences; it shows 

 that it is necessary to separate them as little as possible, that the tendency should 

 be to their simplification, to the reduction into general laws in order to render 

 them easily accessible to every one. 



A very important point, for it is decisive of success or failure in scientific 

 researches, is the choice of a good method. On this subject it is necessary to 

 be guarded against a very common error. We become habituated generally by 

 the usual processes of demonstration to pass from the simple to the composite, 

 to start from a well established principle in order to arrive, from one deduction 

 to another, at the demonstration of more complex propositions. It is in this way 

 that the theorems of geometry are successfully demonstrated; but is it by this 

 method that a science is established ? Far otherwise ; nor do those who make 

 discoveries in the natural sciences proceed in this manner. They observe a 

 great number of facts, compare them, place them side by side, seek the condi- 

 tions which modify each phenomenon, and succeed only in the last place in 

 finding a principle or a law which may guide the understanding in the midst of 

 an embarrassing complexity. 



Medicine, a science which touches us so nearly, since it deals with the troubles 

 which occur in the functions of life, was long misled by that false method 

 which generates systems. Starting from a principle supposed to be true, it pro- 

 ceeded with the most iiTeproachable logic to heap deductions upon deductions, 

 till the moment when eiTor became so obvious that the whole fabric collapsed 

 at once, and the work Avas to be commenced anew. It was a pure metaphor 

 that WTought the evil : " It was proposed to construct the science, and a corner- 

 stone was to be sought to support the edifice." But by what right, among so 

 many materials, was one stone to be taken for this purpose sooner than another 1 

 By what token was it to be recognized as the real base of the structure ? Cer- 

 tainly, by none. If there must be a metaphor, I would prefer to compare the 

 study of the natural sciences to the labor of the archeologists in deciphering 

 inscriptions traced in an unknown language. They try, turn by turn, several 

 senses for each sign ; they seek assistance at the same time from the conditions 

 under which each inscription has been found, and from the analogy it presents 

 with inscriptions already known, and they arrive only in the last place at a 

 knowledge of the principles by which they teach others to decipher the strange 

 language. 



In every science progress is only to be obtained by the employment of certain pro- 

 cesses which act like powerful levers in the service of the human mind : analysis, 

 which serves for research, and synthesis, which is employed to verify the results 

 of analysis, or to set in a more simple light a truth already discovered. But 

 everything is susceptible of improvement, even the means which are at our dis- 

 posal for the realization of furtlier progress. I propose, therefore, summarily 

 to state the present resources of analysis and synthesis, instruments which are 

 so constantly to bo handled by the teachers as well as cultivators of science. 



Analysis consists in reducing to its most simple elements a phenomenon too 



