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comparable to a hydraulic system。 In his On the Motive of Animals； Borelli first attempted to account for the phenomena of life and diseases on these principles。 The iatromechanics held that the great cause of disease is due to different states of elasticity of the solids of the body interfering with the movements of the fluids； which are themselves subject to changes in density； one or both of these conditions continuing to cause stagnation or congestion。 The school thus founded by Borelli was the outcome of the unbounded enthusiasm； with its accompanying exaggeration of certain phenomena with the corresponding belittling of others that naturally follows such a revolutionary discovery as that of Harvey。 Having such a founder as the brilliant Italian Borelli； it was given a sufficient impetus by his writings to carry it some distance before it finally collapsed。 Some of the exaggerated mathematical calculations of Borelli himself are worth noting。 Each heart…beat； as he calculated it； overcomes a resistance equal to one hundred and eighty thousand pounds；the modern physiologist estimates its force at from five to nine ounces！
THOMAS SYDENHAM But while the Continent was struggling with these illusive 〃systems；〃 and dabbling in mystic theories that were to scarcely outlive the men who conceived them； there appeared in Englandthe 〃land of common…sense；〃 as a German scientist has called it〃a cool； clear； and unprejudiced spirit；〃 who in the golden age of systems declined 〃to be like the man who builds the chambers of the upper story of his house before he had laid securely the foundation walls。〃＇1＇ This man was Thomas Sydenham （1624…1689）； who； while the great Harvey was serving the king as surgeon； was fighting as a captain in the parliamentary army。 Sydenham took for his guide the teachings of Hippocrates； modified to suit the advances that had been made in scientific knowledge since the days of the great Greek； and established； as a standard； observation and experience。 He cared little for theory unless confirmed by practice； but took the Hippocratic view that nature cured diseases； assisted by the physician。 He gave due credit； however； to the importance of the part played by the assistant。 As he saw it； medicine could be advanced in three ways： （1） 〃By accurate descriptions or natural histories of diseases； （2） by establishing a fixed principle or method of treatment； founded upon experience； （3） by searching for specific remedies； which he believes must exist in considerable numbers； though he admits that the only one yet discovered is Peruvian bark。〃＇2＇ As it happened； another equally specific remedy； mercury； when used in certain diseases； was already known to him； but he evidently did not recognize it as such。 The influence on future medicine of Sydenham's teachings was most pronounced； due mostly to his teaching of careful observation。 To most physicians； however； he is now remembered chiefly for his introduction of the use of laudanum； still considered one of the most valuable remedies of modern pharmacopoeias。 The German gives the honor of introducing this preparation to Paracelsus； but the English…speaking world will always believe that the credit should be given to Sydenham。
IX。 PHILOSOPHER…SCIENTISTS AND NEW INSTITUTIONS OF LEARNING We saw that in the old Greek days there was no sharp line of demarcation between the field of the philosopher and that of the scientist。 In the Hellenistic epoch； however； knowledge became more specialized； and our recent chapters have shown us scientific investigators whose efforts were far enough removed from the intangibilities of the philosopher。 It must not be overlooked； however； that even in the present epoch there were men whose intellectual efforts were primarily directed towards the subtleties of philosophy； yet who had also a penchant for strictly scientific imaginings； if not indeed for practical scientific experiments。 At least three of these men were of sufficient importance in the history of the development of science to demand more than passing notice。 These three are the Englishman Francis Bacon （1561…1626）； the Frenchman Rene Descartes （1596…1650）； and the German Gottfried Leibnitz （1646…1716）。 Bacon； as the earliest path…breaker； showed the way； theoretically at least； in which the sciences should be studied； Descartes； pursuing the methods pointed out by Bacon； carried the same line of abstract reason into practice as well； while Leibnitz； coming some years later； and having the advantage of the wisdom of his two great predecessors； was naturally influenced by both in his views of abstract scientific principles。 Bacon's career as a statesman and his faults and misfortunes as a man do not concern us here。 Our interest in him begins with his entrance into Trinity College； Cambridge； where he took up the study of all the sciences taught there at that time。 During the three years he became more and more convinced that science was not being studied in a profitable manner； until at last； at the end of his college course； he made ready to renounce the old Aristotelian methods of study and advance his theory of inductive study。 For although he was a great admirer of Aristotle's work； he became convinced that his methods of approaching study were entirely wrong。 〃The opinion of Aristotle；〃 he says； in his De Argumentum Scientiarum； 〃seemeth to me a negligent opinion； that of those things which exist by nature nothing can be changed by custom； using for example； that if a stone be thrown ten thousand times up it will not learn to ascend； and that by often seeing or hearing we do not learn to see or hear better。 For though this principle be true in things wherein nature is peremptory （the reason whereof we cannot now stand to discuss）； yet it is otherwise in things wherein nature admitteth a latitude。 For he might see that a straight glove will come more easily on with use； and that a wand will by use bend otherwise than it grew； and that by use of the voice we speak louder and stronger； and that by use of enduring heat or cold we endure it the better； and the like； which latter sort have a nearer resemblance unto that subject of manners he handleth than those instances which he allegeth。〃＇1＇ These were his opinions； formed while a young man in college； repeated at intervals through his maturer years； and reiterated and emphasized in his old age。 Masses of facts were to be obtained by observing nature at first hand； and from such accumulations of facts deductions were to be made。 In short； reasoning was to be from the specific to the general； and not vice versa。 It was by his teachings alone that Bacon thus contributed to the foundation of modern science； and； while he was constantly thinking and writing on scientific subjects； he contributed little in the way of actual discoveries。 〃I only sound the clarion；〃 he said； 〃but I enter not the battle。〃 The case of Descartes； however； is different。 He both sounded the clarion and entered into the fight。 He himself freely acknowledges his debt to Bacon for his teachings of inductive methods of study； but modern criticism places his work on the same plane as that of the great Englishman。 〃If you lay hold of any characteristic product of modern ways of thinking；〃 says Huxley； 〃either in the region of philosophy or in that of science； you find the spirit of that thought； if not its form； has been present in the mind of the great Frenchman。〃＇2＇ Descartes； the son of a noble family of France； was educated by Jesuit teachers。 Like Bacon； he very early conceived the idea that the methods of teaching and studying science were wrong； but be pondered the matter well into middle life before putting into writing his ideas of philosophy and science。 Then； in his Discourse Touching the Method of Using One's Reason Rightly and of Seeking Scientific Truth； he pointed out the way of seeking after truth。 His central idea in this was to emphasize the importance of DOUBT； and avoidance of accepting as truth anything that does not admit of absolute and unqualified proof。 In reaching these conclusions he had before him the striking examples of scientific deductions by Galileo； and more recently the discovery of the circulation of the blood by Harvey。 This last came as a revelation to scientists； reducing this seemingly occult process； as it did； to the field of mechanical phenomena。 The same mechanical laws that governed the heavenly bodies； as shown by Galileo； governed the action of the human heart； and； for aught any one knew； every part of the body； and even the mind itself。 Having once conceived this idea； Descartes began a series of dissections and experiments upon the lower animals； to find； if possible； further proof of this general law。 To him the human body was simply a machine； a complicated mechanism； whose functions were controlled just as any other piece of machinery。 He compared the human body to complicated machinery run by water…falls and complicated pipes。 〃The nerves of the machine which I am describing；〃 he says； 〃may very well be compared to the pipes of these waterworks； its muscles and its tendons to the other various engines and springs which seem to move them； its animal spirits to the water which impels them； of which the heart is the f