June i, 1888.] 



SCIENCE. 



263 



Mr. Crocker points out. There seems in the list no practical bat- 

 tery that will give a horse-power hour for less than twenty cents, — 

 an enormous price compared with the cost of electric energy from a 

 dynamo. One thing must be borne in mind : the cost of materials 

 is obtained from price-lists of chemical companies, and would be 

 materially decreased if the substances were made in large quanti- 

 ties. It will be seen that it will be impossible, however, to reduce 

 the prices, just at present, to compete with a dynamo supplying 

 energy at less than one cent per horse-power hour : so, while pri- 

 mary batteries have an important and extended field for telephonic 

 purposes, telegraph-lines, bells, etc., they can hardly succeed in the 

 more serious work of supplying power and light. 



The Seel Incandescent-Lamp Filament. — A patent has 

 just been issued in this country for an incandescent-lamp filament 

 which is both novel and successful. The following is the method of 

 preparation : threads of cotton, silk, or other vegetable fibre are 

 steeped in a solution consisting of a silicate or salt, gum-senegal, 

 and caustic soda, and then rolled between warm grooved rollers. 

 The thread is then carbonized in the usual manner. To regulate the 

 resistance of the resulting filament, it is placed in a vessel into 

 which melted paraffine is run, and when the latter hardens an elec- 

 tric current is sent through the filament. As the thread heats, part 

 of the paraffine nearest to it is liquefied, and, as the heat becomes 

 more intense, carbon is deposited on the filament, the solid outer 

 shell of the paraffine preventing any air from getting to it. The 

 resistance gradually decreases as more carbon is deposited. When 

 it reaches its proper value, the current is cut off, the whole of the 

 paraffine melted, and the thread removed. The gum-senegal com- 

 pletely fills the pores of the filament, making it very strong, while 

 the silicate and caustic soda surround the inner core. We have, 

 then, three layers, — the central carbonized thread, the silicate, and 

 the outer layer of deposited carbon. 



The CARRlikRE Accumulator. — Several attempts have been 

 made to produce a secondary battery in which the supports are of 

 carbon instead of lead. A great difficulty in the present types of 

 secondary battery lies in their excessive weight, caused to a great 

 extent by the plates used as a support for the ' active ' material, the 

 inactive support-plates sometimes making up half the weight of the 

 complete cell. Carbon would, for some reasons, make an excellent 

 support for the active material : it is light, a good conductor, and it 

 is not attacked by the acid in the cell. It has been found, however, 

 that carbon plates will quickly disintegrate when used for battery 

 purposes. If the active material is in cavities in the carbon plate, 

 the expansion on discharge will gradually disintegrate the plate ; 

 while, if it is applied on the surface, it will soon drop off. M. Car- 

 riere makes his plates especially dense and hard, and, after apply- 

 ing the active material, he puts them horizontally in a cell with 

 cocoanut-fibre between the plates. Whether this peculiar disposi- 

 tion of the plates and their special construction will be effective, can 

 only be determined by experiment. 



HEALTH MATTERS. 

 Wear and Tear of the Medical Profession. 



The State Board of Health of Illinois has recently published a 

 tabulation and analysis of a mass of material which has been accu- 

 mulating during the past ten years, bearing on the wear and tear of 

 the medical profession of that State. This report, which is written 

 by Dr. John H. Ranch, the able secretary of the board, is a most 

 valuable contribution to the subject, and brings prominently to view 

 the dangers incident to a medical life. Dr. Rauch says that for 

 more than ten years he has been impressed in a general way with 

 a conviction that this wear and tear was underestimated ; that the 

 active practice of medicine was not so conducive to longevity as is 

 popularly supposed, nor as writers on such subjects, basing their 

 conclusions on the data obtained from medical biographies, cyclo- 

 paedias, etc., had been led to believe. 



The source of error in this latter instance is obvious. The sub- 

 jects of biographies, cyclopsedia articles, memoirs, etc., are neces- 

 sarily the men who have attained eminence, or at least prominence ; 

 and, in the nature of the case, prominence in the medical profession 



is largely the fruit of long service and length of days. In other 

 words, the exceptional class which, partly by very reason of long 

 life, has attracted most attention, has been hitherto taken as an in- 

 dication of the longevity of the profession as a whole. Thus we 

 find one writer (Dr. George M. Beard) citing the deaths of 490 

 Massachusetts physicians whose average age at death was 57 years, 

 and 35 out of every 100 of whom attained to 70 years. The aver- 

 age age of the subjects of Gross's ' Medical Biography ' was 59 

 years, although it is ingenuously added that these " included several 

 who died before their prime." Similarly Thacher's ' Medical Bi- 

 ography ' makes mention of 145 physicians, and the fact that their 

 average age at death was 62.8 years is quoted — as are the other 

 instances — as proof of the longevity of medical men. Still another 

 fact should be taken into consideration in the case of the class whc> 

 figure in biographies. It is composed very largely of city physi- 

 cians, and of the men who, in the smaller towns, are in a position 

 to select their practice and adjust their labors with some regard to 

 regular hours of sleep, meals, and relaxation. Comfortably housed 

 at home, properly protected from the weather when making visits,, 

 free from the harassing cares of the ?-es angustcz domi, and beyond 

 the torturing anxiety which too often besets the struggle for practice, 

 — the conditions of life in these cases are undoubtedly favorable to- 

 longevity. But these are the fortunate few, who bear no more nu- 

 merical relation to the rank and file of the profession than the 

 general officers do to the rank and file of an army. 



Coinpared with these biographical subjects, upon whose length 

 of honorable and successful years is predicated the assertion that 

 the wear and tear of the profession does not prevent its members 

 from attaining a high average longevity — compared with these. Dr. 

 Rauch has, as the result of an extensive correspondence and syste- 

 matic record, obtained data which show that the average age at 

 death (in Illinois, at least) is not much over 52 years ; and that only 

 about II, instead of 35, in every 100 attain the scriptural limit of 

 threescore years and ten. 



In older communities it is entirely probable that this rate may be 

 exceeded. In Massachusetts, for example, the average age at death 

 of 1,166 physicians, occurring during a period of nearly thirty-two- 

 years, is given as about 55 years ; but the Illinois statistics — col- 

 lected with painstaking care, and dealing with more than double 

 the number living annually — do not furnish any such favorable 

 result. To a very great extent the discrepancy between Illinois and 

 Massachusetts is due, no doubt, to the different conditions which- 

 obtain in the two communities, — the one a comparatively newly- 

 settled State, with a population containing less than the normal 

 proportion of the middle-aged and beyond ; the other, one of the 

 oldest settled commonwealths, with an excess of ages beyond the 

 middle life, and with what Dr. Holmes calls the " adjustable condi- 

 tions of living " so perfected as to materially conduce to the pro- 

 longation of life. But in addition to this difference there must also- 

 be taken into consideration the radical difference in the modes of 

 collecting the data upon which the average age at death has been 

 computed. 



For Illinois these data have been obtained through official rela- 

 tions with an aggregate of some 14,000 physicians during a period 

 of over ten years. The personnel may be taken as fairly represen- 

 tative of the profession generally, since it is composed of about 

 one-sixth of physicians of a large city, Chicago, and the remainder 

 of physicians of smaller cities and towns. During these ten years 

 there has been an average of 6,000 living per annum, and the ag- 

 gregate deaths have been about 800, or an annual death-rate of 

 13.3 per thousand. These round numbers and the period covered 

 are cited to show that the data are extensive enough to insure sub- 

 stantially trustworthy results in the tabulations and deductions. 



An examination of the tables shows, that while the death-rate of 

 physicians in Illinois for the first few years after entering upon the 

 practice of medicine is lower than that of all males in Illinois, and 

 greatly less than that of the whole population of the country at 

 large, it increases beyond that of the former class during the decade 

 from 40 to 50, and is greater than that of the latter class in the 

 next decade. 



The obvious inference is, that physicians, on entering practice, 

 form a class of selected lives, since they have an advantage of 

 nearly 3 per cent as compared with all males at the same ages, — 



