chinery, which tends to offset the lower wages paid in European countries. In the case of storage batteries there is almost no foreign material offered in the domestic market, so that there may be said to be no foreign competition. The method of construction of standard dry batteries in the United States is more economical of labor than that used in Europe, where the bag type is manufactured, but does not give a cell of quite so much service capacity. The difference is, however, not widely recognized, on account of a fallacious interpretation often given in this country by the less technical users to a test in common use. The small cells used for flash lights are usually of the bag type, and refills for these flash lights are made by the million in Germany by a cheap grade of labor.

European storage-battery makers have two advantages, the lower price of lead in England and Germany and the lower rates of labor.

ELECTRO-MEDICAL APPARATUS.

SUMMARY.

The X-ray tube is the most important apparatus of this class. Other articles are exploring instruments which are electrically lighted, and apparatus for applying electric currents to the body. The X-ray tube is a highly exhausted tube provided with means for passing through it an electric current. The exploring instruments are essentially optical or surgical instruments, incidentally lighted by electricity. Cystoscopes are the most important of these instruments. Equipment for electric treatment consists of apparatus for modifying and controlling the current so that it can be passed through the body; the most important type is the highfrequency apparatus, which includes transformers and rotating machinery.

The use of this latter class of apparatus is still in a somewhat experimental stage.

As reported by the census the production of therapeutic apparatus in the United States amounted to $2,653,098 in 1914, and in 1919 to approximately $5,506,402. In addition about $3,389,000 worth of X-ray tubes were reported in the latter year, these being included under "All other electrical machinery" in 1914. Manufacturers' estimates for 1919, owing probably to different classifications, were only $900,000.

Iron, steel, and copper are the chief materials used for apparatus for electric treatments. Glass, platinum, tungsten, and molybdenum are required for X-ray tubes. For cystoscopic instruments, optical glass and steel are used.

For therapeutic apparatus, machine-shop equipment of standard type is employed. The workmanship is of high grade. Glass manipulation is most important in X-ray tubes. For cystoscopes very high-grade workmanship is required, as the parts must be perfectly fitted to obtain good vision and smooth operation.

X-ray tubes are made largely by one company, which controls the patent on the most advantageous form of tube. An older form of tube is made by several smaller firms. Therapeutic apparatus is made chiefly by three or four makers of electro-medical apparatus of moderate size.

There is some export, but no figures are available.

A limited amount of high-frequency apparatus is imported from Great Britain and some cystoscopes come from Germany. Before the war there was considerable importation of German cystoscopes. Great Britain, Germany, and France produce electro-medical apparatus. Cystoscopes and other instruments requiring a lens system are the most important class of electro-medical instruments made in Germany, and those in which German makers especially excel.

The manufacture and importation of X-ray tubes are controlled largely by patents held by one company. These patents cover the Coolidge tube, which possesses great advantages over other types and is in general use.

There have been recent reports that a new type of tube, superior to the Coolidge tube, has been developed in Germany. Cystoscopes were imported quite largely before the war, on account of the high quality of the German instruments. The quality of the domestic

product has been improved, however, and at present there does not appear to be any well-recognized superiority in the foreign instruments. The tariff problem in regard to cystoscopes relates to surgical instruments rather than to electro-medical apparatus.

High frequency apparatus for electrical treatment has not been an actively competitive product.

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GENERAL INFORMATION.

Act of 1913, paragraph 167. Articles or wares not specially provided for in this section, if composed wholly or in chief value of iron, steel, lead, copper, brass, nickel, pewter, zinc, aluminum, or other metal, but not plated with gold or silver, and whether partly or wholly manufactured, 20 per centum ad valorem. Paragraph 95. * and all glass or manufactures of glass or paste or of which glass or paste is the component material of chief value, not specially provided for in this section, 30 per centum ad valorem.

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DESCRIPTION.

Electro-medical apparatus includes the X-ray tube, various forms of small special lighting apparatus for illuminating and examining parts of the body, cauteries, control switchboards for dental and other motors, apparatus for generating various forms of electric current and for applying it to the body, and other apparatus. Among the most important and widely known is the X-ray tube. It consists of a glass tube or bulb, from which nearly all the air has been exhausted, and having sealed within it two metal terminals, between which a high-tension electric current is passed through the rarefied gas in the tube.

From one of these terminals, called the cathode, there radiates a stream of electrons, which is directed against the other terminal, called the anode, usually a heavy block of tungsten or molybdenum. This anode, while receiving the stream of electrons, is the source of the X rays, which pass out through the glass in straight lines. The penetrability of substances to the X rays bears no relation to their penetrability to light, but varies with the density of the substance, so that it is possible to obtain photographs, or shadow pictures, of the interior of opaque bodies.

There are two types of X-ray tube, the gas tube and the Coolidge tube. In the gas tube there is an atmosphere of gas at low pressure through which the high-tension discharge passes. The regulation of the pressure, or vacuum, in the gas tube, which controls the character of the X rays, is a matter of some difficulty and uncertainty, and the tubes require repumping and adjusting from time to time. In the Coolidge tube the cathode is a tungsten filament, similar to that in an incandescent lamp, which may be heated by the passage of a small current. The vacuum is constant at a very high value, and the regulation is effected by varying the temperature of the filament by means of the filament current. An increase in the temperature allows a greater current to pass through the vacuum. This regulation can be effected quite simply and definitely, which gives this type of tube a great advantage over the gas type. In addition to the diagnostic uses of the X rays, for obtaining photographs, the action of the rays themselves has been found of great use in the treatment of certain forms of skin diseases, and progress is being made in their application to other diseases, in which it is hoped that highly important results will be obtained.

There are many forms of apparatus for applying electric currents to the body for therapeutic purposes, among the most noteworthy are those for generating the high-frequency currents, in which the current reverses in direction millions of times per second, as compared with a hundred or more in power circuits. Currents of this nature up to one horsepower or more may be passed through the body without injury, and may be used to generate heat within the interior of the body, and for other purposes. While the benefits of this form of treatment have perhaps not been as universal as was expected, it is of undoubted use in some conditions, and is still in process of development.

Another important form of electro-medical instrument is the cystoscope, a diagnostic instrument for observing and operating on interior parts of the body. It consists of a system of small tubes, carrying an electric lamp near the end, and equipped with a lens system for observation, and means for introducing fluids or instruments. It is more properly a surgical than an electrical instrument, as the only electrical features are the lamp and the conductors thereto.

Other forms of electro-medical apparatus are dental and surgical motors, for machining bone, various forms of diagnostic lamps, and other less important types.

DOMESTIC PRODUCTION.

In 1914 the production of electrotherapeutic apparatus amounted to $2,653,098, having more than doubled during the previous five years. In 1919 value of the product was $5,506,000, and in addition X-ray tubes were produced valued at $3,389,000, which were not separately reported in the previous census. Electro-medical apparatus is of the highest importance in diagnosis, and its usefulness in other fields is likely to increase.

Materials. In the construction of apparatus for high-frequency treatment and for energizing X-ray tubes, the chief materials are steel, often special alloys, for the magnetic material, copper wire, and insulating materials. A considerable amount of hardwood, mahogany, oak, etc., is used for cabinets. X-ray tubes are glass, usually inclosed by a lead-glass shield to prevent injury to the operator by stray radiation. Some of the glass for tubes is imported from Germany, and is said to be superior for work requiring high penetration, such as therapeutic X-ray treatment. The other materials are almost wholly of domestic origin, and the supply is adequate. Small quantities of tungsten, molybdenum, and other materials are required, but the amounts are insignificant.

Equipment. The shop equipment, small metal and wood working machinery, is all of American manufacture, and of the best quality

available.

Methods of production.-The demand for this class of apparatus, although wide, is not sufficient to permit the quantity production methods employed in other branches of the electrical industry. Automatic machinery is not used to any great extent, and considerable skilled hand labor is necessary, especially in finishing cystoscopes and other instruments requiring fine adjustment. In this respect European methods of manufacture are similar to those employed in the United States.

Organization. The demand for most classes of this apparatus is small, and most of the concerns specializing in its manufacture are of moderate size. The reputation of the maker is a factor of more importance than large scale production. It is not possible to state separately the capital invested.

Geographical distribution. The industry is located in New England and the other northern manufacturing States.

History of the industry.-Electromedical apparatus has been made for a long period, but until the development of the X ray, the high frequency current, and the electrically lighted cystoscope it was of limited application and uncertain usefulness. The important branches of the industry therefore have a history of only about 25

years.

Domestic production and consumption.-Production in in 1919 amounted to $8,895,402. Domestic production is sufficient to supply the demand, although the domestic glass is said to be not as suitable as the German product for X-ray tubes, which require high penetration for therapeutic purposes.

Domestic exports. No figures are available regarding exports. It is known, however, that some apparatus is exported.

FOREIGN PRODUCTION.

Germany and France are the largest foreign producers. Their product is high grade and has been frequently preferred to that of domestic manufacturers. The industry is highly developed in Germany, and German makers have maintained a reputation for excellence that has been a valuable asset to them.

IMPORTS.

Before the war there were considerable imports, but statistics are not reported separately. The greater part of these imports have consisted of cystoscopes and similar apparatus requiring a high-grade lens system, It is evident that imports have been decreasing, as American manufacturers have improved their product and developed new apparatus. There is a limited amount of high frequency apparatus imported from Great Britain, made by the firm of Cox Cavendish.

PRICES.

Definite price comparisons are practically impossible, owing to differences in design and quality which make it difficult to estimate accurately. X-ray apparatus is sold at from about $600 for the smaller outfits up to $2,500 and more for the larger. High frequency apparatus may be priced up to $500 or more, according to the size and design, and cystoscopes up to $150 or more. Domestic prices of cystoscopes and similar instruments have increased approximately 25 per cent since the beginning of the war (1917). One importer submitted statements to the commission that cystoscopic instruments of similar type cost 25 per cent more from domestic makers than the prices for which they could be obtained in Germany at the present time (1921).