NATURAL HISTORY OF ORGANIZED RODIES. 299 



gauge Laving sncli a length that the liquid column shall represent a rather 

 strong pressure, when tlie ludion is plunged to a certain depth. The volume of 

 air contained in the ball is so regulated that the ludion, -when at the surface of 

 the water, is a little less dense than the liquid, and emerges from it to some 

 extent. Let it be now sunk to a slight depth ; it is still not so dense as the 

 water and tends to rise above its surface. Sink it a little deeper, and it Avill 

 remain nearly immovable in the zone in which it is placed, indicating that its 

 density is now equal to that of the water. It is thus that it is represented in 

 the figure. Let it be sunk more deeply and it Avill be seen to have a tendency 

 to descend of itself: it has become denser than the water. 



Here, then, we have a new example of the synthetic reproduction of the phe- 

 nomena Avhich occur in living animals. Many analogous examples might be 

 cited, but it is only my purpose here to signalize the utility of this method, and 

 to show how important it is still further to extend its application. It may be 

 added that any one, by the construction of a schema of his own, will find that 

 the vague ideas which he may have at first conceived on an obscure subject, 

 acquire singular precision and development. New conceptions will be con- 

 stantly presenting themselves, and problems be suggested which the mind is 

 impatient to verify by new experiments. In a word, this manual labor of the 

 construction of schematic apparatus, far from absorbing the mind, sustains and 

 guides it by furnishing it at each step with an experimental test. 



An objection will not fail to be made by those who pretend that there are, 

 in living l)eings, properties which such persons term vital, and ^\hich are alto- 

 gether peculiar. They will tell us that S3'nthesis may well reproduce the physi- 

 cal phenomena which accompany life, but that it is incapable of imitating the 

 vital phenomena. I will answer, for my own part, that I recognize but two 

 sorts of manifestations of life: those which are intelligible to us, being all of a 

 physical or chemical order; and those which are not intelligible. As regards 

 the last, it is better to avow our ignorance than to disguise it under a semblance 

 of explanation. 



, IV. — Laws in biology. 



I have next to speak of si/nfhcsls considered as a mental operation, the oppo- 

 site of analysis; as collecting dispersed ideas to form of them a whole; as ascend- 

 ing from particular facts to the general law which governs all of them. 



The highest point which the natural sciences can reach is the discovery of 

 the laws which govern the phenomena of life. This, as I have said, is the 

 ideal we should })ursue, but which we have not yet attained. At present it is 

 the research for facts which occupies- us; we labor in behalf of successors, per- 

 haps far remote ; we accumulate for them the materials of a vast synthesis, Avhich 

 will enable them to embrace all these facts under a general point of view, and 

 to educe from them simple laws. Already, however, light seems to diffuse itself 

 upon certain points of the sciences in question, and some of their laws have begun 

 to emerge from the mass of details. 



Let us premise this cai)ital fact, that the laws of physics and of chemistry 

 reappear in the manifestations of animal or vegetable life, and that every day 

 the hypothesis which led to the admission of forces of a special nature in organ- 

 ized beings is becoming less and less necessary. As regards the laws of physics, 

 we have seen them applied in the operation of the schematic apparatus by means 

 of which we are enabled to imitate certain phenomena observed in living beings. 

 We shall doubtless still continue to discover these same law's in jjroportion as we 

 shall study in their more intimate details the functions of organized beings. As 

 regards the laws of chemistry, Berthelot has shown them as presiding in the 

 formation of the substances called organic. The hypothesis of a vital cTiemistry 

 of a wholly peculiar nature is now useless. Researches based on synthesis in 

 chemistry show us that the ordinary laws suffice to explain the formation of 

 organic matter in the interior of vegetables. 



