Document LpVgZqQOZJ1XXvXQVReN5B0Xg

374 OCCUPATIONAL TUMORS AND ALLIED DISEASES There cannot be any doubt about the almost universal increase in the frequency of pulmonary neoplasms. An analysis of the data recorded readily shows that marked variations do exist in the incidence of these tumors between various cities and regions of one country and between different countries and continents, which as yet are not explained [Stocks; Bonser (England); Dissmann (Czechoslovakia); and Fischer (Germany)]. It is quite puzzling that pulmonary cancer is rather rare among the inhabitants of Italy (Carolo), not extraordinarily common in France, but frequent among the rest of Europe. Similar discrepancies exist, according to Fischer, in Germany where the lung cancer rate is high in some greatly industrialized districts (Saxony; and Rhineland-Westphalia), but low in some of the industrial regions of northern Germany. Such observations do not permit the conclusion that industrializa tion does not play any causative role in the increase of pulmonary cancers (Fischer). The existing knowledge of industrial carcinogenic agents is now sufficiently exact and extensive to emphasize the importance of specific agents against the vague conception of nonspecific, chronic, irritative, occupational factors. The lumping together of highly different, exogenous, industrial agencies, such as exist in various mixtures and compositions in any large industrial district, for the purpose of evaluating environmental carcinogenic influences, must result in a confusion of the issue; i.e., unless proper care is taken to compare districts containing the same types of industries working with identical methods and materials and employing approximately an equal number of workers. Plausible explanations will be found for these now obscure divergences, when our methods of analysis of the extraneous conditions exist ing in these regions have become more intelligent and exact. The increase of cancers of the respiratory tract has not remained restricted to those of the lung. Kennaway and Kennaway concluded, from an analysis of the death certificates of England and Wales, that from 1921 to 1932 laryngeal cancers increased 1.4 fold in males and 1.75 fold in females. 3. SYMPTOMATOLOGY The diagnosis of lung carcinomas is considered difficult and the correct diagnosis is missed frequently. Several factors are responsible for this fact. First, numerous diseases of the lung may produce symptoms similar to those of lung carcinoma. Secondly, the symptoms caused by these tumors vary considerably, corresponding to the different locations of these neoplasms in the lung, their histological character, proliferative activity, type of local and gen eral extension, secondary changes in the lung as sclerosis, abscess or gangrene formation, and pleural effusion, and metastatic alterations in other organs. In some, no clinical symptoms may be produced during life especially those of the senile type, or the first clinical symptoms do not emanate from the primary focus but from metastases in distant organs, such as the brain and bones. In others, the first and sometimes only symptoms are represented by uncharacter istic pains in the thoracic wall, pains similar to those present in intercostal