a history of science-4-第41章
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Almost at the same time that the Polish medical student was demonstrating the itch mite in Paris； it chanced； curiously enough； that another medical student； this time an Englishman； made an analogous discovery of perhaps even greater importance。 Indeed； this English discovery in its initial stages slightly antedated the other； for it was in 1833 that the student in question； James Paget； interne in St。 Bartholomew's Hospital； London； while dissecting the muscular tissues of a human subject； found little specks of extraneous matter； which； when taken to the professor of comparative anatomy； Richard Owen； were ascertained； with the aid of the microscope； to be the cocoon of a minute and hitherto unknown insect。 Owen named the insect Trichina spiralis。 After the discovery was published it transpired that similar specks had been observed by several earlier investigators； but no one had previously suspected or； at any rate； demonstrated their nature。 Nor was the full story of the trichina made out for a long time after Owen's discovery。 It was not till 1847 that the American anatomist Dr。 Joseph Leidy found the cysts of trichina in the tissues of pork； and another decade or so elapsed after that before German workers； chief among whom were Leuckart； Virchow； and Zenker； proved that the parasite gets into the human system through ingestion of infected pork； and that it causes a definite set of symptoms of disease which hitherto had been mistaken for rheumatism； typhoid fever； and other maladies。 Then the medical world was agog for a time over the subject of trichinosis； government inspection of pork was established in some parts of Germany； American pork was excluded altogether from France； and the whole subject thus came prominently to public attention。 But important as the trichina parasite proved on its own account in the end； its greatest importance； after all； was in the share it played in directing attention at the time of its discovery in 1833 to the subject of microscopic parasites in general。
The decade that followed that discovery was a time of great activity in the study of microscopic organisms and microscopic tissues； and such men as Ehrenberg and Henle and Bory Saint…Vincent and Kolliker and Rokitansky and Remak and Dujardin were widening the bounds of knowledge of this new subject with details that cannot be more than referred to here。 But the crowning achievement of the period in this direction was the discovery made by the German； J。 L。 Schoenlein； in 1839； that a very common and most distressing disease of the scalp； known as favus； is really due to the presence and growth on the scalp of a vegetable organism of microscopic size。 Thus it was made clear that not merely animal but also vegetable organisms of obscure； microscopic species have causal relations to the diseases with which mankind is afflicted。 This knowledge of the parasites was another long step in the direction of scientific medical knowledge； but the heights to which this knowledge led were not to be scaled； or even recognized； until another generation of workers had entered the field。
PAINLESS SURGERY
Meantime； in quite another field of medicine； events were developing which led presently to a revelation of greater immediate importance to humanity than any other discovery that had come in the century； perhaps in any field of science whatever。 This was the discovery of the pain…dispelling power of the vapor of sulphuric ether inhaled by a patient undergoing a surgical operation。 This discovery came solely out of America； and it stands curiously isolated； since apparently no minds in any other country were trending towards it even vaguely。 Davy； in England； had indeed originated the method of medication by inhalation； and earned out some most interesting experiments fifty years earlier； and it was doubtless his experiments with nitrous oxide gas that gave the clew to one of the American investigators； but this was the sole contribution of preceding generations to the subject； and since the beginning of the century； when Davy turned his attention to other matters； no one had made the slightest advance along the same line until an American dentist renewed the investigation。
In view of the sequel； Davy's experiments merit full attention。 Here is his own account of them； as written in 1799：
〃Immediately after a journey of one hundred and twenty…six miles； in which I had no sleep the preceding night； being much exhausted； I respired seven quarts of nitrous oxide gas for near three minutes。 It produced the usual pleasurable effects and slight muscular motion。 I continued exhilarated for some minutes afterwards； but in half an hour found myself neither more nor less exhausted than before the experiment。 I had a great propensity to sleep。
〃To ascertain with certainty whether the more extensive action of nitrous oxide compatible with life was capable of producing debility； I resolved to breathe the gas for such a time； and in such quantities； as to produce excitement equal in duration and superior in intensity to that occasioned by high intoxication from opium or alcohol。
〃To habituate myself to the excitement； and to carry it on gradually； on December 26th I was enclosed in an air…tight breathing…box； of the capacity of about nine and one…half cubic feet； in the presence of Dr。 Kinglake。 After I had taken a situation in which I could by means of a curved thermometer inserted under the arm； and a stop…watch； ascertain the alterations in my pulse and animal heat； twenty quarts of nitrous oxide were thrown into the box。
〃For three minutes I experienced no alteration in my sensations； though immediately after the introduction of the nitrous oxide the smell and taste of it were very evident。 In four minutes I began to feel a slight glow in the cheeks and a generally diffused warmth over the chest； though the temperature of the box was not quite 50 degrees。 。 。 。 In twenty…five minutes the animal heat was 100 degrees； pulse 124。 In thirty minutes twenty quarts more of gas were introduced。
〃My sensations were now pleasant； I had a generally diffused warmth without the slightest moisture of the skin； a sense of exhilaration similar to that produced by a small dose of wine； and a disposition to muscular motion and to merriment。
〃In three…quarters of an hour the pulse was 104 and the animal heat not 99。5 degrees； the temperature of the chamber 64 degrees。 The pleasurable feelings continued to increase； the pulse became fuller and slower； till in about an hour it was 88； when the animal heat was 99 degrees。 Twenty quarts more of air were admitted。 I had now a great disposition to laugh； luminous points seemed frequently to pass before my eyes； my hearing was certainly more acute； and I felt a pleasant lightness and power of exertion in my muscles。 In a short time the symptoms became stationary； breathing was rather oppressed； and on account of the great desire for action rest was painful。
〃I now came out of the box； having been in precisely an hour and a quarter。 The moment after I began to respire twenty quarts of unmingled nitrous oxide。 A thrilling extending from the chest to the extremities was almost immediately produced。 I felt a sense of tangible extension highly pleasurable in every limb； my visible impressions were dazzling and apparently magnified； I heard distinctly every sound in the room； and was perfectly aware of my situation。 By degrees； as the pleasurable sensations increased； I lost all connection with external things； trains of vivid visible images rapidly passed through my mind and were connected with words in such a manner as to produce perceptions perfectly novel。
〃I existed in a world of newly connected and newly modified ideas。 I theorized； I imagined that I made discoveries。 When I was awakened from this semi…delirious trance by Dr。 Kinglake； who took the bag from my mouth； indignation and pride were the first feelings produced by the sight of persons about me。 My emotions were enthusiastic and sublime； and for a minute I walked about the room perfectly regardless of what was said to me。 As I recovered my former state of mind； I felt an inclination to communicate the discoveries I had made during the e
