a history of science-4-第1章
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A History of Science； Volume 4
by Henry Smith Williams； M。D。； LL。D。
ASSISTED BY EDWARD H。 WILLIAMS； M。D。
IN FIVE VOLUMES VOLUME IV。
MODERN DEVELOPMENT OF THE CHEMICAL AND BIOLOGICAL SCIENCES
A HISTORY OF SCIENCE
BOOK IV
MODERN DEVELOPMENT OF THE CHEMICAL AND BIOLOGICAL SCIENCES
AS regards chronology； the epoch covered in the present volume is identical with that viewed in the preceding one。 But now as regards subject matter we pass on to those diverse phases of the physical world which are the field of the chemist； and to those yet more intricate processes which have to do with living organisms。 So radical are the changes here that we seem to be entering new worlds； and yet； here as before； there are intimations of the new discoveries away back in the Greek days。 The solution of the problem of respiration will remind us that Anaxagoras half guessed the secret； and in those diversified studies which tell us of the Daltonian atom in its wonderful transmutations； we shall be reminded again of the Clazomenian philosopher and his successor Democritus。
Yet we should press the analogy much too far were we to intimate that the Greek of the elder day or any thinker of a more recent period had penetrated； even in the vaguest way； all of the mysteries that the nineteenth century has revealed in the fields of chemistry and biology。 At the very most the insight of those great Greeks and of the wonderful seventeenth…century philosophers who so often seemed on the verge of our later discoveries did no more than vaguely anticipate their successors of this later century。 To gain an accurate； really specific knowledge of the properties of elementary bodies was reserved for the chemists of a recent epoch。 The vague Greek questionings as to organic evolution were world…wide from the precise inductions of a Darwin。 If the mediaeval Arabian endeavored to dull the knife of the surgeon with the use of drugs； his results hardly merit to be termed even an anticipation of modern anaesthesia。 And when we speak of preventive medicineof bacteriology in all its phaseswe have to do with a marvellous field of which no previous generation of men had even the slightest inkling。
All in all； then； those that lie before us are perhaps the most wonderful and the most fascinating of all the fields of science。 As the chapters of the preceding book carried us out into a macrocosm of inconceivable magnitude； our present studies are to reveal a microcosm of equally inconceivable smallness。 As the studies of the physicist attempted to reveal the very nature of matter and of energy； we have now to seek the solution of the yet more inscrutable problems of life and of mind。
I。 THE PHLOGISTON THEORY IN CHEMISTRY
The development of the science of chemistry from the 〃science〃 of alchemy is a striking example of the complete revolution in the attitude of observers in the field of science。 As has been pointed out in a preceding chapter； the alchemist； having a preconceived idea of how things should be； made all his experiments to prove his preconceived theory； while the chemist reverses this attitude of mind and bases his conceptions on the results of his laboratory experiments。 In short； chemistry is what alchemy never could be； an inductive science。 But this transition from one point of view to an exactly opposite one was necessarily a very slow process。 Ideas that have held undisputed sway over the minds of succeeding generations for hundreds of years cannot be overthrown in a moment； unless the agent of such an overthrow be so obvious that it cannot be challenged。 The rudimentary chemistry that overthrew alchemy had nothing so obvious and palpable。
The great first step was the substitution of the one principle； phlogiston； for the three principles； salt； sulphur； and mercury。 We have seen how the experiment of burning or calcining such a metal as lead 〃destroyed〃 the lead as such； leaving an entirely different substance in its place； and how the original metal could be restored by the addition of wheat to the calcined product。 To the alchemist this was 〃mortification〃 and 〃revivification〃 of the metal。 For； as pointed out by Paracelsus； 〃anything that could be killed by man could also be revivified by him； although this was not possible to the things killed by God。〃 The burning of such substances as wood； wax； oil； etc。； was also looked upon as the same 〃killing〃 process； and the fact that the alchemist was unable to revivify them was regarded as simply the lack of skill on his part； and in no wise affecting the theory itself。
But the iconoclastic spirit； if not the acceptance of all the teachings； of the great Paracelsus had been gradually taking root among the better class of alchemists； and about the middle of the seventeenth century Robert Boyle （1626…1691） called attention to the possibility of making a wrong deduction from the phenomenon of the calcination of the metals； because of a very important factor； the action of the air； which was generally overlooked。 And he urged his colleagues of the laboratories to give greater heed to certain other phenomena that might pass unnoticed in the ordinary calcinating process。 In his work； The Sceptical Chemist； he showed the reasons for doubting the threefold constitution of matter； and in his General History of the Air advanced some novel and carefully studied theories as to the composition of the atmosphere。 This was an important step； and although Boyle is not directly responsible for the phlogiston theory； it is probable that his experiments on the atmosphere influenced considerably the real founders； Becker and Stahl。
Boyle gave very definitely his idea of how he thought air might be composed。 〃I conjecture that the atmospherical air consists of three different kinds of corpuscles；〃 he says； 〃the first； those numberless particles which； in the form of vapors or dry exhalations； ascend from the earth； water； minerals； vegetables； animals； etc。； in a word； whatever substances are elevated by the celestial or subterraneal heat； and thence diffused into the atmosphere。 The second may be yet more subtle； and consist of those exceedingly minute atoms； the magnetical effluvia of the earth； with other innumerable particles sent out from the bodies of the celestial luminaries； and causing； by their influence； the idea of light in us。 The third sort is its characteristic and essential property； I mean permanently elastic parts。 Various hypotheses may be framed relating to the structure of these later particles of the air。 They might be resembled to the springs of watches； coiled up and endeavoring to restore themselves； to wool； which； being compressed； has an elastic force； to slender wires of different substances； consistencies； lengths； and thickness； in greater curls or less； near to； or remote from each other； etc。； yet all continuing springy； expansible； and compressible。 Lastly； they may also be compared to the thin shavings of different kinds of wood； various in their lengths； breadth； and thickness。 And this； perhaps； will seem the most eligible hypothesis； because it； in some measure； illustrates the production of the elastic particles we are considering。 For no art or curious instruments are required to make these shavings whose curls are in no wise uniform； but seemingly casual； and what is more remarkable； bodies that before seemed unelastic； as beams and blocks； will afford them。〃＇1＇
Although this explanation of the composition of the air is most crude； it had the effect of directing attention to the fact that the atmosphere is not 〃mere nothingness；〃 but a 〃something〃 with a definite composition； and this served as a good foundation for future investigations。 To be sure； Boyle was neither the first nor the only chemist who had suspected that the air was a mixture of gases； and not a simple one； and that only certain of these gases take part in the process of calcination。 Jean Rey； a French physician； and John Mayow； an Englishman； had preformed experiments which showed conclusively that the air was not a simple substance； but Boyle's work was better known； and in its effect probably more important。 But with all Boyle's explanations of the compositi
