We have various methods for approaching the cancer problem. We can observe the frequency with which human cancer appears, its symptoms, and conditions which precede it. We can study the finer structure and mode of development of cancer with the microscope on pieces of tumor which have been excised. We can study cancer from a comparative point of view, its occurrence in animals and plants. The comparative study leads to the experimental investigation of cancer in animals.
1. Frequency, Distribution, Varieties of Human Cancer
Cancer among man is found in all countries where a closer search for it has been instituted. The frequency with which it occurs differs, however, very much among people living under the ordinary conditions of present civilization in Europe and America and among races or nations living under more primitive conditions, especially in Africa and Asia.
If we consider first the former category we find that approximately 3.1-5 per cent, of all human beings die from cancer. We are struck by the relative uniformity in the percentage of deaths from cancer, which indicates that within certain limits the conditions causing cancer are relatively constant and uniformly distributed over the civilized world. In this respect cancer resembles certain diseases which are caused by organisms evenly distributed over wide areas and to diseases primarily due to internal factors and not or only secondarily to parasitic agencies, while it differs from such diseases as smallpox, bubonic plague and poliomyelitis which are very irregular in their appearance.
If we compare the death rate from cancer in various countries we find the following figures: In a population of 10,000 die from cancer each year: in Switzerland 13.2, Norway 10, Holland 10.1, England 9.1, Austria 7.8, France 7.6, Prussia 7.1, Italy 6.1, Spain 4.8, Algiers (European inhabitants) 3.2. The death rate is also relatively low in Russia, Hungary, Servia, Jamaica and Ceylon. In Kyoto (Japan) it is approximately like Austria 7.9 per 10,000 inhabitants. On the whole the death rate from cancer is low in the countries around the Mediterranean.
In the United States in an area comprising one half of the population, the death rate per 10,000 inhabitants was (according to a report by the Health Commissioner of Pennsylvania (Dr. S. C. Dixon), 7.31 in 1907; the death rate in the United States is therefore very similar to that of Germany and Austria. Approximately 75,000 people die from cancer in one year in the United States and about half a million in the civilized world (F. L. Hoffman). If we consider only persons over 45 years old, considerably more people in the registered area of the United States die from cancer than from tuberculosis. Between the age of 45 and 60 years almost 7 per cent, of the male and 16 per cent, of the female population die in this country from cancer.
