Conflicting and contradictory testimony from competent authority is not uncommon in therapeutics, and the reasons for it are well recognized in the impossibility of an equality in the conditions and circumstances of the investigations, and hence the general decision commonly reached is upon the principle of averages.

There can hardly be a reasonable doubt that coca, in common with tea and coffee and other similar articles, has a refreshing, recuperative, and sustaining effect upon human beings, and when well cultivated, well cured, and well preserved, so as to reach its uses of good quality and in good condition, it is at least equal to good tea, and available for important therapeutic uses.  Mr. Dowdeswell supposed that he used good coca, but it is very easy to see that with any amount of care and pains he may have been mistaken in this.  Had he but used the same parcel of coca that Sir Robert Christison did, the results of the two observers would be absolutely incomprehensible; and the results, in the absence of any testimony on that point, simply prove that the two observers were using a different article, though under the same name, and possibly with the same care in selection.  On Sir Robert Christison’s side of the question there are many competent observers whose testimony is spread over many years; while on Mr. Dowdeswell’s side there are fewer observers.  But there has been no observer on either side whose researches have been anything like so thorough, so extended, or so accurate as those of Mr. Dowdeswell.  Indeed, no other account has been met with wherein the modern methods of precision have been applied to the question at all; the other testimony being all rather loose and indefinite, often at second or third hands, or from the narratives of more or less enthusiastic travelers.  But if Mr. Dowdeswell’s results be accepted as being conclusive, the annual consumption of 40,000,000 pounds of coca at a cost of 10,000,000 dollars promotes this substance to take rank among the large economic blunders of the age.[9]

[Footnote 9:  An excellent summing up of the character and history of coca, from which some of the writer’s information has been obtained, will be found in “Medicinal Plants,” by Bentley and Trimen, vol. i., article 40.]

The testimony in regard to the effects of tea, coffee, Paraguay tea, Guarana and Kola nuts, is all of a similar character to that upon coca.  Each of these substances seems to have come into use independently, in widely separated countries, to produce the same effects, namely, to refresh, renew, or sustain the physical and mental organism, and it was a curious surprise to find, after they had all been thus long used, that although each came from a different natural order of plants, the same active principle—­namely, caffeine—­could be extracted in different proportions from all.  It is now still more curious, however, to find that for centuries another plant, namely coca, yielding