Leather Industry

LEATHER INDUSTRY includes the dressing of various types of leather (sole leather, half-hide, harness leather, rawhide, chrome leather, suede, kid leather, etc.). The main process of leather processing is tanning, which represents a complex physicochemical process of combining the tanning agent with the leather fiber. The task of the tanning process is to protect the leather from decay and impart the required technical properties (elasticity, water resistance, strength, etc.). Various tanning methods are reduced to three main ones: 1) with tanning acids (vegetable, red tanning), 2) with mineral salts (chromium and iron salts, alums), and 3) with animal and vegetable fats (chamois tanning). In addition, their combination is possible. The most widespread method to this day is vegetable tanning, used mainly in the dressing of heavy leathers (sole, half-hide, harness, etc.). For this purpose, tanning materials are used in the form of bark (“bark”) of various trees (willow, oak, spruce, quebracho, mimosa, etc.). The crushed bark is poured into vats and filled with water; in this process, the extraction of tanning acids takes place, yielding an infusion called tanning juice in production. This juice is used directly for tanning leather; concentrated juice is called tanning extract. Leather tanning is carried out: 1) in vats filled with tanning juice ("zalichka"), 2) by interspersing individual hides in vats with a layer of crushed bark followed by filling with water ("pit tanning"), and 3) in rotating drums with tanning juice (rapid tanning, retanning). Tanning is preceded by a number of operations aimed at preparing the leather to absorb tanning agents. These include: 1) soaking the hide in water ("soaking") to saturate with moisture and remove preserving substances, 2) removing hair by processing in vats with a solution of milk of lime ("liming") or smearing the hide with sodium sulfide mixed with lime, 3) fleshing, i.e., removing subcutaneous tissue with a sharp knife ("podhodka"), 4) Bating and puering, i.e., treating the leather ("pelt") with weak organic acids, aiming to remove lime residues after liming and loosening the leather fibers before tanning; this is achieved by immersing the leather in vats with flour or bran mixed in water ("kiseli"), in which weak acids develop due to fermentation processes. In this form, the leather goes to tanning, after which it is dried, fat-liquored, and subjected to mechanical finishing (rolling, shaving, stretching, softening, etc.). In mineral tanning, the preliminary and subsequent processing of hides does not differ essentially from that in vegetable tanning. The most common method of mineral tanning is chrome tanning. Chrome tanning is currently carried out by two methods: one of them is called two-bath, the other single-bath. The first consists in placing the hides in a vat with a solution of potassium dichromate (potassium bichromate) and hydrochloric acid and, after impregnation, transferring them to a second, reduction bath containing a solution of hyposulfite with hydrochloric acid; in the first bath, chromic acid is released and penetrates into the thickness of the leather, and in the second, it is converted into basic chromium sulfate, which is the tanning agent. The second method consists in placing the hides in a drum or vat filled with a solution of chrome alum, soda, and sodium chloride. The main occupational hazards of the leather industry, associated both directly with production processes and with the current sanitary condition of tanneries, are: 1) dampness and getting wet, 2) the release of gases (H₂S, NH₃, etc.), 3) substances having an irritating effect on the skin, 4) the danger of anthrax infection, and 5) heavy physical labor and an unfavorable general sanitary environment. The specific hazards of the wet workshops of tanneries (soaking, liming, bating, tanning) are dampness and getting wet. Wetting of significant body surfaces occurs during the manual loading and unloading of vats and washing vats. These hazards explain the higher incidence of rheumatism among leather workers compared to other professions. According to the statistics of the Leipzig Sick Fund, the incidence of rheumatism among leather workers is 2 times higher than that among all insured workers. According to Goltsman's data concerning a large tannery (2,300 workers), wet workshops in 1908–10 yielded 10.4 cases of rheumatism per 100 workers per year, while other workshops yielded only 3.9. In connection with the rotting and fermentation processes taking place during leather processing, H₂S, NH₃, and CO₂ are released into the air of the workshops. Under normal conditions, however, these gases are contained in the air in concentrations that do not have direct toxic significance; the chronic effect of small concentrations of these substances has not been investigated to date. Over the past few years, a series of acute, partly fatal poisonings occurred in the USSR during the cleaning of tanning vats. However, studies carried out did not reveal such concentrations of H₂S that could exert such a strong toxic effect; the clinical picture also did not fully correspond to H₂S poisoning. One may think that there is a combined action of a complex of poisons: H₂S, cyanide, and other, still poorly investigated gases that are products of the life activity of the microflora of tanning vats. Skin diseases are extremely common among leather workers as a consequence of their constant contact with liquids, largely contaminated, and exposure to irritating substances (sodium sulfide, lime, potassium bichromate, etc.). According to Leites' data at the Moscow "Truzhenik" plant, out of 160 examined workers, 98 were found to have various skin diseases (ulcers), leather hardening (zadublivanie), maceration, nail diseases, etc. Skin lesions are most common in chrome tanning. The two-bath method is particularly unfavorable because the workers' hands during the sorting of leather are exposed to chromic acid obtained in the first bath (potassium bichromate + hydrochloric acid). This leads to the formation of specific chrome ulcers, located predominantly in the interdigital folds and responding very poorly to treatment under production conditions. One of the serious dangers of leather production is the danger of anthrax infection in the event that infected hides are received for processing. According to urgent reports on occupational poisonings and diseases for 1926/27 in the RSFSR, 67 cases of occupational anthrax were registered, of which 55 belong to the leather and sheepskin-fur coat industries. Of the 60 cases of anthrax registered in Moscow in 1924, 9 are related to work with leather. In pre-revolutionary times, cases of anthrax among leather workers were apparently more widespread, although exact statistics were lacking; thus, one Slobodskoy uyezd of the former Vyatka Governorate, which had many artisanal leather and sheepskin-fur coat factories, yielded 1,173 cases over 10 years (1898–1907). In Germany, out of 1,684 cases of occupational anthrax registered from 1910 to 1923, leather workers account for 621 cases; in England (1910–20), out of 998 cases, leather workers give 212; in France (1910–22), out of 443 cases, 261. The most dangerous in this regard are the work processes preceding tanning. Liming of hides does not prevent danger, since milk of lime in the applied concentrations is not able to kill anthrax spores. The most typical localization of the anthrax carbuncle in leather workers is the hands and neck; the latter due to the frequently practiced carrying of hides on the shoulder. As for the factor of heavy physical labor and extremely unfavorable general sanitary conditions in tanneries, they do not affect the pathology of leather workers to any noticeable extent. In general, both old studies (Erisman, Dementyev, Pogozhev, Loshchilov) and modern dispensary data show good physical development and a relatively low pathological morbidity of leather workers. According to foreign data (England-1910–12, Leipzig Sick Fund-1887–1905), the mortality of leather workers is significantly lower than the average figures for the entire working population. This is explained, of course, by specific natural occupational selection: people of strong constitution who are able to withstand the harmful influences of working conditions and yield a relatively favorable health picture despite these hazards go predominantly into the leather industry.

Health-improving measures regarding dampness and wetting: installation of waterproof floors and good drains for liquids, appropriate special clothing and a correct regime for its use; for the latter purpose, changing rooms and special dryers for special clothing must be provided at the factories. To prevent poisonings when cleaning vats (lime, bating, tanning), the vat must be thoroughly washed with water before a worker descends into it; the work itself must be performed with the necessary precautions (working in a mask with a supply of fresh air, signaling, a preliminary biological test by lowering small animals such as a rat, guinea pig, rabbit, etc., into it). Work with caustic and irritating substances must be performed in appropriate mittens or gloves. Rational special clothing for work in wet shops and for special protection in the indicated case has been developed by the Institute of Labor Protection (Moscow). Regarding the prophylaxis of anthrax, measures to strengthen veterinary and sanitary supervision are of the greatest importance. In this regard, in particular, the application of the Ascoli-Valenti precipitin reaction (see Ascoli-Valenti reaction) for identifying hides originating from animals sick with anthrax is very expedient. The disinfection of suspicious hides has not achieved wide distribution up to the present time due to its high cost and reduction in the quality of the goods. Among the numerous methods of disinfection (see), the Schattenfroh method enjoys the greatest fame. Measures of personal precaution for workers are also of great importance. Detailed sanitary rules for the layout and maintenance of leather factories are contained in the mandatory decree of the People's Commissariat of Labor of the USSR of August 18, 1926. To prevent the harmful influence of leather factories on the surrounding population due to the pollution of public water bodies by waste waters, the latter must undergo purification in accordance with the decree of the People's Commissariat of Health and the People's Commissariat of Labor of June 30, 1922. The root cause of the sanitary ill-being of the leather industry lies in the extremely primitive, unmechanized, semi-handicraft methods of production even at large leather factories with a large number of workers employed in them. Therefore, the main health-improving prospect lies in transferring the leather industry onto broad industrial tracks, in the consolidation of enterprises, and the widespread implementation of measures for the rationalization and mechanization of production.

A. Letavet. KOZHEVNIKOV, Aleksey Yakovlevich (1836–1902), founder of the clinic of nervous diseases and the psychiatric clinic of the 1st Moscow State University and the founder of the Moscow neurological school. Kozhevnikov graduated from the medical faculty in Moscow (1858), and in 1860 he took the position of assistant in the therapeutic hospital clinic of Moscow University, where he took a special interest in diseases of the nervous system. In 1865, Kozhevnikov defended his dissertation: «Disease described by Duchenne under the name Ataxie locomotrice progressive» (diss., Moscow, 1865). In 1866, he was sent abroad by the university to prepare for teaching nervous and mental diseases and studied with Kölliker, du Bois-Reymond, Virchow, Griesinger, and others. Abroad, Kozhevnikov also familiarized himself with the organization of the care of the mentally ill and the arrangement of psychiatric institutions. Upon returning from abroad (1869), Kozhevnikov was elected privat-docent of nervous and mental diseases; simultaneously, he also lectured on private pathology and therapy of internal diseases and was elected extraordinary professor for this department, and in 1884, with the opening of the department of nervous and mental diseases, he transferred to this latter one and thus was the first professor in these disciplines. Kozhevnikov began giving lectures at the Novo-Ekateringinsky Hospital, where he had a total of 20 beds for patients. To increase his clinical experience, Kozhevnikov worked as a consultant in various institutions, in particular at the Staro-Ekateringinsky Hospital, where, upon his initiative, a nervous ward rich in clinical material was arranged. Through Kozhevnikov's efforts, a psychiatric clinic (1887) was built at the Devichye Pole in Moscow attached to the university, the plan for which was worked out by himself. For some time, Kozhevnikov managed two clinics, and in 1888 he handed over the lecturing on psychiatry and the management of the psychiatric clinic to S. S. Korsakov. Then Kozhevnikov proceeded to build there, on Devichye Pole, the clinic of nervous diseases (opened in 1890). Subsequently, he attached an asylum for chronic neurological patients to the clinic with private donations in order to improve teaching. In 1892, a museum was opened at the clinic of nervous diseases, which was subsequently assigned the name «Neurological Museum named after Prof. A. Ya. Kozhevnikov». Kozhevnikov himself began collecting funds to build a separate building for the neurological museum. The realization of the latter was successfully accomplished by Kozhevnikov's successor, V. K. Roth (already after Kozhevnikov's death), under the name «Neurological Institute named after A. Ya. Kozhevnikov». Upon Kozhevnikov's initiative, the Society of Neuropathologists and Psychiatrists arose, of which he served as chairman until his death; besides, he was an honorary member of 15 scientific societies in Russia and abroad. Kozhevnikov's scientific works are distinguished by a special thoroughness; he did not rush to publish his works, but carefully thought them over and verified them, which is why the number of his published works is small, but each work is a contribution to science. Kozhevnikov received worldwide fame thanks to the description of a special form of epilepsy—epilepsia partialis continua—which received the name «Kozhevnikov's epilepsy» in world literature. Out of 39 published works by Kozhevnikov, 25 are scientific and 14 are articles and speeches read on various occasions. Besides medicine, Kozhevnikov was interested in ethnography, comparative anatomy, and archeology, taking part in excavations in various parts of Russia, read reports on this subject, and donated a large number of skulls of various centuries and nationalities to the Neurological Museum. Kozhevnikov's significance for science is conditioned not only by his scientific works, but also by the creation of a school whose brilliant representatives enjoyed worldwide fame: S. S. Korsakov, V. K. Roth, L. O. Darkshevich, V. A. Muratov, G. I. Rossolimo. Among Kozhevnikov's works, besides the dissertation, the following works must be noted: «Ein Fall von lateraler amyotrophischer Sklerose» (Centralbl. f. Nervenheilk., 1885, no. 18); «Ophthalmoplegia nuclearis» (Meditsinskoe obozrenie, vol. XXVII, nos. 2–3, 1887; also in Progrès médical, 1887, no. 36); «A special form of cortical epilepsy» (Meditsinskoe obozrenie, vol. XLII, no. 14, 1894); «Diplegia spastica progressiva» (ibid., vol. XLIII, no. 4, 1895); «Asthenic bulbar paralysis» (ibid., vol. XLV, no. 10, 1896); «The Neurological Museum of Moscow University» (jointly with G. Pribytkov, Moscow, 1897).