Let us try a 10 per cent. solution of salt. Suppose the maximum current this will carry is ¼ ampere per square inch, which will give a cross section of the solution of at least 60 ÷ ¼ = 240 square inches. Now, the specific resistance per inch cube (i.e., the resistance between two opposite surfaces of a cube whose side measures 1 inch) of the 10 per cent. solution of salt used in test No. 3 was 2.12 ohms. The drop, CR, will be 2.12 x ¼ = 0.53 volt per inch length of solution between electrodes. Hence, the electrodes will have to be 40/0.53 = 75 inches apart. This would require about three barrels connected in series. This was taken merely as an illustration, because its specific resistance was known when the current density was ¼ ampere per square inch. This solution, however, will carry safely 1/3 ampere per square inch, but I used the previous figure, since I did not know its specific resistance for this current density, because its specific resistance will be lower for a larger current density on account of the higher temperature which it will have, for the resistance of a solution decreases as its temperature increases.
To reduce this length would require a solution of higher specific resistance, that is, a solution containing less than 10 per cent. of salt, and an increase in the cross section, since the maximum carrying capacity also diminishes as the percentage of salt diminishes. Only approximate calculations are useful because variations in temperature, amount of salt actually in solution and the rate at which heat can be radiated, all combine to give results which may vary widely from those calculated.
As a matter of fact, it is seldom necessary or advisable to use a solution containing over 2 or 3 per cent. of salt. The best way to add salt to a liquid rheostat is to make a strong solution in a separate vessel and add as much of this solution as is needed. This avoids the annoying increase in conductivity of the solution which happens when the salt itself is added and is gradually dissolved.
Liquid rheostats are ever so much more satisfactory for alternating than for direct current testing. The electrodes and solution are practically free from decomposition, and a given cross section seems to be able to carry a larger alternating than direct current—probably due partly to the absence of the scum on the surface which hinders the radiation of heat.
[1] In American Electrician.
THE PROGRESS OF MEDICAL EDUCATION IN THE UNITED STATES.
A retrospective survey of the progress made and of the reforms instituted in medical education in the United States is instructive. In many respects there is cause for much congratulation, while for other reasons the situation gives rise to feelings of alarm. It is pleasing to note and it augurs well for the future that a decided advance has been made in the direction of a more thorough medical training, yet at the same time it is discouraging to observe that, despite these progressive steps, competition does not abate, but rather daily becomes more acute. Dr. William T. Slayton has just issued his small annual volume on "Medical Education and Registration in the United States and Canada." From a study of this book, which fairly bristles with facts, a sufficiently comprehensive opinion may be formed in regard to the present state of medical education in this country. According to this work, there is now a grand total of one hundred and fifty-four medical schools. Of this number, one hundred and seventeen require attendance on four annual courses of lectures, and twenty-seven require attendance on sessions of eight months, and ten on nine months each year. Twenty-nine States and the District of Columbia require an examination for license to practice medicine; eighteen of these require both a diploma from a recognized college and an examination. Fifteen States require a diploma from a college recognized by them or an examination. Five States, viz., Vermont, Michigan, Kansas, Wyoming and Nevada, have practically no laws governing the practice of medicine; Alaska the same. In order to gain a clear comprehension of the existing state of affairs, a comparison of the number of students at two periods, with a lapse of years intervening sufficient to eliminate all minor variations, will be more to the point than merely regarding the multiplication of schools. Many of these mushroom institutions are not worthy of notice, containing perhaps a dozen students, and brought into existence only for the purpose of profit or from other motives of self-interest. The number of students is as reliable an index as can be given. For instance, taking the decade between 1883-84 and 1893-94, it will be found that the students in regular schools in 1883-84 numbered 10,600; in 1893-94 they had increased to 17,601. Students in homoeopathic schools in 1883-84 were 1,267; in 1893-94, 1,666. The number of eclectic students was stationary at the two periods. The increase during the period from 1893-94 to the present time has been at about the same ratio.
These figures reveal more plainly than words the existing condition of affairs, which must, too, in the nature of things, continue until that time when all the States fall into line and resolve to adopt a four years' course of not less than eight months.
To make yet another comparison, the total number of medical schools in Austria and Germany, with a population exceeding that of this country, is twenty-nine. Great Britain, with more than half the population, has seventeen; while Russia, with one hundred million inhabitants, has nine. Of course we do not argue that America, with her immense territory and scattered population, does not need greater facilities for the study of medicine than do thickly inhabited countries, as Germany and Great Britain; but we do contend that when a city of the size of St. Louis has as many schools as Russia, the craze for multiplying these schools is being carried to absurd and harmful lengths. However, that the number of schools and their yearly supply of graduates of medicine are far beyond the demand is perfectly well known to all. The Medical Record and other medical journals have fully discussed and insisted upon that point for a considerable time. The real question at issue is by what means to remedy or at least to lessen the bad effects of the system as quickly as possible. The first and most important steps toward this desirable consummation have been already taken, and when a four years' course comes into practice throughout the country, the difficult problem of checking excessive competition will at any rate be much nearer its solution. Why should France, Germany, Great Britain and other European nations consider that a course of from five to seven years is not too long to acquire a good knowledge of medical work, while in many parts of America two or three years' training is esteemed ample for the manufacture of a full-fledged doctor? Such methods are unfair both to the public and to the medical profession, and the result is that in numerous instances the short-time graduate has either to learn most of the practical part of his duties by hard experience, to starve, or to utilize his abilities in some more lucrative path of life. Taking into consideration the fact that the theory and practice of medicine have become so extended within recent years, it must be readily conceded that four years is barely sufficient time in which to gain a satisfactory insight into their various departments. For a person, however gifted, to hope to receive an adequate medical training in two or three years is vain.