802 



STATISTICS. 



bers ; fcicd eyenltfecks? persons \vho. ape most 

 given to* express "doubts of the necessity or 

 expediency of resorting to them, find them- 

 selves constrained to sanction by their own 

 practice what they condemn in theory. This 

 is an all-sufficient answer to those who con- 

 tent themselves with objecting in general 

 terms to the employment of numbers in me- 

 dical investigations. As to more minute and 

 detailed objections, these will be found to be 

 anticipated and disarmed by the simple con- 

 sideration that they apply in reality not to 

 the use, but to the abuse of numbers. The 

 time has long gone by, when the absolute 

 dependence of all science on observation and 

 experiment could admit of question or dis- 

 pute ; and, as no one in the present day 

 claims for physiology and medicine any im- 

 munity from the severe conditions which the 

 very nature of things imposes, we are spared 

 those appeals to authority which might for- 

 merly have been required at our hands. The 

 absolute necessity of observation and experi- 

 ment towards the improvement of the science 

 and art of medicine, in the widest acceptation 

 of those terms, may, therefore, be safely taken 

 for granted. The only points upon which any 

 serious difference of opinion or divergence of 

 practice exists, are the degree of care and 

 accuracy which should be brought to bear on 

 individual observations and experiments, the 

 properties which fit single facts to be thrown 

 into groups or classes ; the language which 

 ought to be employed in expressing the ge- 

 neral results of such classifications ; and the 

 number of facts which, being so grouped or 

 classified, may be required to establish a ge- 

 neral proposition, or to furnish an accurate 

 test or trustworthy standard of comparison. 



The human mind is so constituted, that it 

 looks forward to an occurrence with a con- 

 fidence proportioned to the number of times 

 that it has been previously known to happen. 

 Hence, the universal belief that all living 

 beings will die, and that the sun will rise and 

 set to-morrow ; hence, the somewhat less 

 sanguine expectation that quinine will cure 

 ague, and that vaccination will either pre- 

 vent or modify small-pox ; hence, the little 

 hope we have that a severe attack of Asiatic 

 cholera will terminate favourably, and our 

 absolute despair of the recovery of a patient 

 seized with hydrophobia. In these, and other 

 analogous cases, we have either the expe- 

 rience of all mankind in all times and places, 

 or that of large numbers of men in addition 

 to our own. We do not require that the in- 

 dividual occurrences which have created our 

 confidence, our misgiving, or our despair, 

 should be committed to paper, arranged in 

 columns, and embodied in sums or averages. 

 For practical purposes we are satisfied with 

 our own impressions. But should a doubt be 

 expressed, and supported by a show of reason 

 or experience, whether vaccination possess 

 the virtue generally attributed to it ; should 

 some new preventive measure or mode of 

 treatment be recommended in cholera, as su- 

 perior to other plans previously adopted ; we 



ask for the specific facts which have seemed 

 to warrant the doubts of the one party, and 

 the recommendation of the other. If these 

 facts are few, we naturally view them with 

 mistrust, and are disposed to attribute them, 

 at the best, to some coincidence ; or if, being 

 more in number, their actual amount is stated 

 in vague and general terms, we as naturally 

 demand the precise figures. We feel instinc- 

 tively, that common and familiar words are 

 altogether wanting in precision ; that they 

 take their meaning from the character of 

 those who use them ; that, in a word, " the 

 sometimes of the cautious is the often of the 

 sanguine, the always of the empiric, and the 

 never of the sceptic ; while the numbers, 

 1, 10, 100, 1000, have but one meaning for 

 all mankind." 



But this mistrust of vague generalities of 

 expression, is not the only form in which the 

 more cautious and logical spirit of modern 

 times embodies itself. The same misgivings 

 are felt and expressed as to the propriety of 

 committing the facts which are to serve as the 

 materials of our theories to the uncertain keep- 

 ing of the memory. We feel that a science 

 built up of such materials, bears to true science 

 the same sort of relation which tradition bears 

 to history. It may not be destitute of valu- 

 able truths and sound principles, but it must 

 fail in that precision and delicacy of discrimi- 

 nation which forms the peculiar attribute of 

 true science as of true history. The history 

 of medicine abounds with examples of impor- 

 tant principles of treatment, and valuable re- 

 medies discovered solely by the light of 

 experience, based upon the mere recollection 

 of a number of individual occurrences. In 

 this way the efficacy of bark and arsenic in 

 ague, of mercury in syphilis, and of iodide of 

 potassium in certain forms of secondary disease 

 was discovered. Indeed, it may be confidently 

 affirmed that all our knowledge of remedies is 

 traceable to this source ; and it is probable 

 that we shall continue to be indebted to it for 

 all future discoveries of importance. It is the 

 natural method of discovery, and, as such, will 

 necessarily maintain its ground. But a very 

 little reflection will convince us of the utter 

 inadequacy of this method to meet the strict 

 requirements of the science, and the ever- vary- 

 ing exigencies of the art of medicine. We 

 may be able by its aid to sketch the broad out- 

 lines, and mark the salient points of a science, 

 but we cannot hope to fill in the details with 

 all the lights and shadows which go to make 

 up the perfect landscape. Still less can we 

 satisfy ourselves or others as to the real merits 

 of disputed questions by an appeal to un- 

 written or loosely recorded experience. We 

 all feel that there is no solution for our doubts 

 short of an appeal to observations carefully 

 and faithfully recorded, and summed up in the 

 clear and simple language of figures. The use 

 of mercury in syphilis, supplies us with an apt 

 illustration of this truth. An experience, 

 founded upon unrecorded and unnumbered 

 occurrences, first recommended this remedy 

 for the treatment of that disease ; but it would 



