that the serum treatment will stand as the culminating achievement in therapeutics of our century。 It is the logical outgrowth of those experimental studies with the microscope begun by our predecessors of the thirties； and it represents the present culmination of the rigidly experimental method which has brought medicine from a level of fanciful empiricism to the plane of a rational experimental science。
IX。 THE NEW SCIENCE OF EXPERIMENTAL PSYCHOLOGY
BRAIN AND MIND
A little over a hundred years ago a reform movement was afoot in the world in the interests of the insane。 As was fitting； the movement showed itself first in America； where these unfortunates were humanely cared for at a time when their treatment elsewhere was worse than brutal； but England and France quickly fell into line。 The leader on this side of the water was the famous Philadelphian； Dr。 Benjamin Rush； 〃the Sydenham of America〃； in England； Dr。 William Tuke inaugurated the movement； and in France； Dr。 Philippe Pinel； single…handed； led the way。 Moved by a common spirit； though acting quite independently； these men raised a revolt against the traditional custom which； spurning the insane as demon…haunted outcasts； had condemned these unfortunates to dungeons； chains； and the lash。 Hitherto few people had thought it other than the natural course of events that the 〃maniac〃 should be thrust into a dungeon； and perhaps chained to the wall with the aid of an iron band riveted permanently about his neck or waist。 Many an unfortunate； thus manacled； was held to the narrow limits of his chain for years together in a cell to which full daylight never penetrated； sometimesiron being expensivethe chain was so short that the wretched victim could not rise to the upright posture or even shift his position upon his squalid pallet of straw。
In America； indeed； there being no Middle Age precedents to crystallize into established customs； the treatment accorded the insane had seldom or never sunk to this level。 Partly for this reason； perhaps； the work of Dr。 Rush at the Philadelphia Hospital； in 1784； by means of which the insane came to be humanely treated； even to the extent of banishing the lash； has been but little noted； while the work of the European leaders； though belonging to later decades； has been made famous。 And perhaps this is not as unjust as it seems； for the step which Rush took； from relatively bad to good； was a far easier one to take than the leap from atrocities to good treatment which the European reformers were obliged to compass。 In Paris； for example； Pinel was obliged to ask permission of the authorities even to make the attempt at liberating the insane from their chains； and； notwithstanding his recognized position as a leader of science； he gained but grudging assent； and was regarded as being himself little better than a lunatic for making so manifestly unwise and hopeless an attempt。 Once the attempt had been made； however； and carried to a successful issue； the amelioration wrought in the condition of the insane was so patent that the fame of Pinel's work at the Bicetre and the Salpetriere went abroad apace。 It required； indeed； many years to complete it in Paris； and a lifetime of effort on the part of Pinel's pupil Esquirol and others to extend the reform to the provinces； but the epochal turning…point had been reached with Pinel's labors of the closing years of the eighteenth century。
The significance of this wise and humane reform； in the present connection； is the fact that these studies of the insane gave emphasis to the novel idea； which by…and…by became accepted as beyond question； that 〃demoniacal possession〃 is in reality no more than the outward expression of a diseased condition of the brain。 This realization made it clear； as never before； how intimately the mind and the body are linked one to the other。 And so it chanced that； in striking the shackles from the insane； Pinel and his confreres struck a blow also； unwittingly； at time…honored philosophical traditions。 The liberation of the insane from their dungeons was an augury of the liberation of psychology from the musty recesses of metaphysics。 Hitherto psychology； in so far as it existed at all； was but the subjective study of individual minds； in future it must become objective as well； taking into account also the relations which the mind bears to the body； and in particular to the brain and nervous system。
The necessity for this collocation was advocated quite as earnestly； and even more directly； by another worker of this period； whose studies were allied to those of alienists； and who； even more actively than they； focalized his attention upon the brain and its functions。 This earliest of specialists in brain studies was a German by birth but Parisian by adoption； Dr。 Franz Joseph Gall； originator of the since…notorious system of phrenology。 The merited disrepute into which this system has fallen through the exposition of peripatetic charlatans should not make us forget that Dr。 Gall himself was apparently a highly educated physician； a careful student of the brain and mind according to the best light of his time； and； withal； an earnest and honest believer in the validity of the system he had originated。 The system itself； taken as a whole； was hopelessly faulty； yet it was not without its latent germ of truth； as later studies were to show。 How firmly its author himself believed in it is evidenced by the paper which he contributed to the French Academy of Sciences in 1808。 The paper itself was referred to a committee of which Pinel and Cuvier were members。 The verdict of this committee was adverse； and justly so； yet the system condemned had at least one merit which its detractors failed to realize。 It popularized the conception that the brain is the organ of mind。 Moreover； by its insistence it rallied about it a band of scientific supporters； chief of whom was Dr。 Kaspar Spurzlieim； a man of no mean abilities； who became the propagandist of phrenology in England and in America。 Of course such advocacy and popularity stimulated opposition as well； and out of the disputations thus arising there grew presently a general interest in the brain as the organ of mind； quite aside from any preconceptions whatever as to the doctrines of Gall and Spurzheim。
Prominent among the unprejudiced class of workers who now appeared was the brilliant young Frenchman Louis Antoine Desmoulins； who studied first under the tutorage of the famous Magendie； and published jointly with him a classical work on the nervous system of vertebrates in 1825。 Desmoulins made at least one discovery of epochal importance。 He observed that the brains of persons dying in old age were lighter than the average and gave visible evidence of atrophy； and he reasoned that such decay is a normal accompaniment of senility。 No one nowadays would question the accuracy of this observation； but the scientific world was not quite ready for it in 1825； for when Desmoulins announced his discovery to the French Academy； that august and somewhat patriarchal body was moved to quite unscientific wrath； and forbade the young iconoclast the privilege of further hearings。 From which it is evident that the partially liberated spirit of the new psychology had by no means freed itself altogether； at the close of the first quarter of the nineteenth century； from the metaphysical cobwebs of its long incarceration。
FUNCTIONS OF THE NERVES
While studies of the brain were thus being inaugurated； the nervous system； which is the channel of communication between the brain and the outside world； was being interrogated with even more tangible results。 The inaugural discovery was made in 1811 by Dr。 （afterwards Sir Charles） Bell；＇1＇ the famous English surgeon and experimental physiologist。 It consisted of the observation that the anterior roots of the spinal nerves are given over to the function of conveying motor impulses from the brain outward； whereas the posterior roots convey solely sensory impulses to the brain from without。 Hitherto it had been supposed that all nerves have a similar function； and the peculiar distribution of the spinal nerves had been an unsolved puzzle。
Bell's discovery was epochal； but its full significance was not appreciated for a decade； nor； indeed； was its validity at first admitted。 In Paris； in particular； then the court of final appeal in all matters scientific； the alleged discovery was looked at askance； or quite ignored。 But in 1823 the subject was taken up by the recognized leader of French physiologyFrancois Magendiein the course of his comprehensive experimental studies of the nervous system； and Bell's conclusions were subjected to the most rigid experimental tests and found altogether valid。 Bell himself； meanwhile； had turned his attention to the cranial nerves； and had proved that these also are divisible into two setssensory and motor。 Sometimes； indeed； the two sets of filaments are combined into one nerve cord； but if traced to their origin these are found to arise from different brain centres。 Thus it was clear that a hitherto unrecognized duality of function pertains to the entire extra…cranial nervous system。 Any impulse sent from the periphery to the brain must be conveyed along a perfectly definite channel； the response from the brain； sent out to the peripheral muscles； must traverse an equally definite and altogether different course。 If either channel is interruptedas by the section of its particular nerve tractthe corresponding message is denied transmission as effectually as an electric current is stopped by the section of the transmitting wire。
Experimenters everywhere soon confirmed the observations of Bell and Magendie； and； as always happens after a great discovery； a fresh impulse was given to investigations in allied fields。 Nevertheless； a full decade elapsed before another discovery of comparable importance was made。 Then Marshall Hall； the most famous of English physicians of his day； made his classical observations on the phenomena that henceforth were to be known as reflex action。 In 1832； while experimenting one day with a decapitated newt； he observed that the headless creature's limbs would contract in direct response to certain stim