286 NATURAL HISTORY OF ORGANIZED BODIES. 



complex to lie ollierwisc comprehended. If the multiplicity of simultaneous 

 incidents perplexes our understanding-, avc endeavor to abstract one of these 

 incidents, observe it as exactly as possible, then, passing to another, study it in 

 the same manner. In thus overcoming- successively the difficulties which pre- 

 sent themselves, and which in combination exceed our efforts at comprehension, 

 consists the fimction of analysis, and it is this which constitutes the source of its 

 power. 



But, in this conflict of details, difficulties of another order still present them- 

 selves. These arise froni the msufficiency of our senses, baffled alike by objects 

 too small or too large, too near or too remote, as well as by movements too slow 

 t)r too rapid. Man has found the means of creating for himself more powerful 

 senses in order to detect the truth which evades him. He has rendered his 

 vision more penetrating by help of the telescope which sounds the immensity of 

 space, and of the microscope which explores the infinitely little. Balance and 

 compass in hand, he estimates with precision the weight and volume of bodies, 

 which his touch indicated to him in only a rough manner. The more advanced 

 the state of any science, the more it has need of instruments, for it has passed 

 beyond the horizon embraced by the unassisted view of our predecessors. It 

 has transcended the limits of the circle in which the human intellect was so 

 long exercised, while exhausting itself in contemplating the surface of the same 

 objects and consuming in sterile dialectics the power which to-day it employs in 

 rigorous observation. 



Instruments are the indispensable intermediaries between mind and matter ; 

 the physicist, the chemist, the astronomer can effect but little without their suc- 

 cor ; the anatomist, the physiologist, the physician have recourse to them as 

 indispensable to the progress of medical science. The invention of cadaveric 

 injections and that of the microscope have imiugurated a new era for anatomy, 

 which owes to the use of these expedients the comparative perfection which 

 it has attained in our, day. The same is the case with physiology; it is 

 to the manometer, the thermometer, to electric machines of various construction, 

 apparatus for registering, &:c., that the phj'siologist is indebted for the power 

 of substituting experimentation, in its proper sense, for observation, always 

 slower and often powerless to discover the laws which govern life. 



To show the progress already realized in tht? method of analysis, and to mark 

 the multiplicity of resources of which it may avail itself, we take a few 

 examples : 



In chemistry, when the object is to recognize the nature of certain bodies 

 which enter into a combination or mixture, we proceed, by quaJifativc analysis, 

 to disengage each of these bodies and to isolate them successively. Then, by 

 qitaniifnticc analysis, avc determine in what quantity each substance existed in 

 the mixture. In making this discrimination, the ])alanco is at our service. 

 This, we see, is an apparatus borrowed from physics which enables the chemist 

 to arrive at exact determinations. But the helpful intervention of physics stops 

 not there. In virtue of that solidarity of the sciences, of which I have before 

 spoken, the chemist resorts to the physicist for the aid of still other instruments. 

 If, for instance, we have the solution of a known salt whose degree of concen- 

 tration we would ascertain, there is no need to destroy the mixture and 

 extract the salt, in order afterwards to weigh it ; we seek, by means of the are- 

 ometer, the density of the mixture, and, knowing the density proper to the salt, 

 it is easy to calculate the quantity contained in the solution. If in another 

 solution substances exist which are crystallizable together with others which are 

 not so, the use of the dial/jscr enables us to eliect their separation. This again 

 is an apparatus of i)hysics placed at the service of chemistry. The poJarUneter 

 is also of great utility. It enables us to appreciate in an instant the existence 

 of certain substances contained in a solution, and to determine their proportion 

 with rigorous exactness. Lastly, the spectroscoiie contributes a new power to 



