derived only from reference to the climatic attributes obtaining in the populous cities of selected districts where other conditions offer a suitable basis for comparison as to the tuberculosis mortality rate. Judged by this token, the evidence is conclusive regarding the relative degree of immunity conferred through the influence of altitude combined with dryness and sunshine. The infrequency of tuberculosis in parts of Algiers, the Russian Steppes, Iceland, and Hebrides, all at low altitudes, is explained by the small number of inhabitants and the absence of crowding or industrial pursuits. In like manner the slight prevalence of the disease in the elevated regions of Africa and India may be ascribed to the same cause. Observations, however, concerning the frequency of consumption in large centers of population at low elevations in the interior, and in such cities at moderate altitudes as Denver, City of Mexico, Santa Fé, Colorado Springs, Albuquerque, and Las Vegas, are properly eligible for comparison. Gardiner has written in no uncertain tone of the remarkably low mortality rate from non-imported consumption in Colorado Springs, at an altitude of 6000 feet. The development of indigenous pulmonary tuberculosis in Denver, a city of tall buildings, large mercantile establishments, department stores, and factories, with 200,000 inhabitants, many of whom represent cases of imported consumption, has been the subject of some difference of belief among medical observers. Some years ago the opinion was promulgated by highly efficient health officers that non-imported tuberculosis was increasing at a prodigious rate. This view was indorsed to some extent by a committee appointed by the State Medical Society in 1901 to investigate and report concerning the actual status of such development. At the invitation of the El Paso County Medical Society I conducted a systematic investigation concerning the matter, and reported the results of my endeavor in an address delivered before the Society at Colorado Springs in the latter part of 1901. This was repeated by request before the Denver and Arapahoe County Medical Society in January of the following year. The questions involved are of such importance that in discussing the data concerning the development of indigenous tuberculosis in Colorado I find it advisable to utilize a portion of the material contained in my previous study of the subject.

CHAPTER XI

TO WHAT EXTENT IS CONSUMPTION INDIGENOUS IN COLORADO?

It was formerly asserted by some that pulmonary tuberculosis contracted in Colorado constituted a very important factor in mortality statistics. An indigenous disease was thought to be increasing at such a rate and assuming such proportions as to demand for its restriction drastic measures in the way of legislative and municipal supervision. Although heartily in sympathy with all rational measures of control, I have been unable to accept the evidence presented to substantiate the alleged increasing prevalence of such cases. It may be

admitted that consumption has been contracted in Colorado, as in other centers of population, and that to some extent it may be expected to originate here in the future. It is only with reference to the degree and practical significance of its development that an unprejudiced inquiry is solicited. Although consumption is communicable, it nevertheless is acquired chiefly by those rendered susceptible through environment, occupation, previous conditions, and other unfavorable influences. The infection is known to be often slow and incremental in character, prolonged exposure and in some instances repeated infection being necessary to overcome individual resistance sufficiently to produce clinical manifestations of the disease. It is to be expected, therefore, that consumption should occasionally develop in Colorado as a natural result of the massing of population, embracing all classes, from affluence to poverty, and including all degrees of predisposition. The disease should not be ascribed solely to an intimate association with imported pulmonary invalids, although there must inevitably develop frequent disregard of precautionary measures. A considerable number of the people in Colorado pursue a peculiarly unfavorable occupation, to which may be attributed to some extent the occasional development of pulmonary phthisis. Miners are subjected for prolonged periods to entire absence of sunshine and to the inhalation of an atmosphere deficient in oxygen and vitiated by dampness, dust, and smoke. Exposure to such conditions day after day cannot fail to exert a deleterious influence throughout the respiratory tract and produce a soil notoriously favorable for infection. A large portion of the younger population in Colorado are born of tuberculous parents, and in early life, when especially predisposed, subjected to continued undue exposure. As a legitimate result of these factors the origin of segregated cases of consumption is conceded, but this constitutes no argument detrimental to the value of altitude, sunshine, and dryness. The fact that the disease has not attained greater proportions is a remarkable tribute to the restraining influence of a beneficent climate. Present interest attaches to a consideration as to whether or not consumption developed in Colorado is increasing to any material. extent from year to year. Upon the answer to this question depends in great measure the proper attitude of the local profession with reference to a problem extremely difficult of solution and capable of affording honest differences of opinion. It is at once evident that the situation demands a calm, judicial inquiry, the evidence presented to consist of a cold analysis of statistical facts and not dogmatic opinions or preconceived ideas.

During the past fifteen years public attention has been repeatedly drawn to an alleged rapid increase in the number of deaths from consumption contracted in Colorado.

A review of the material offered as evidence to establish the large proportion of cases originating in this State to those contracted elsewhere indicates that the chief source of information is found in the former records of the Denver Health Department. In the annual report for 1896 it was stated that the number of deaths during the previous year from tuberculosis developed in Colorado "is a little more than one-sixth of the total tuberculous death-rate." It was noted also that the percentage of deaths from tuberculosis contracted in this State had been progressively increasing. In 1893 the proportion was stated to be 11.25 per cent.; in 1894, 13.7 per cent.; in 1895, 15 per cent.; in 1896, 18.4 per cent. Later

reports from the Health Department showed the proportion in 1897 to be 18 per cent., and in 1898, 19.7 per cent. The source of information upon which these statistics were compiled was the returns upon the death-certificates.

The percentage of deaths is by no means a fair criterion of the proportion in Denver of cases said to have developed in Colorado to those contracted elsewhere. The pulmonary invalid from a distance, with a hopeless prognosis, is usually advised to return home. Comparatively few such patients, fortunately, are permitted to die in Denver, removed from family and friends. The proportion, then, of one to six does not properly apply, as might be inferred, to the existing cases of tuberculosis in Colorado.

It is easy to demonstrate the fallacy of an alleged rapid increase in the percentage of deaths from tuberculosis contracted here. It is apparent that a given ratio may be radically transformed by a change in either of its terms. In other words, the percentage of deaths from tuberculosis developed in Colorado may be increased from year to year by reason of an increase in the number of such deaths, provided the total tuberculous death-rate remains unchanged. Upon the other hand, if the entire death-rate from tuberculosis is diminished, the proportion of indigenous cases may be increased, although the actual number be less than in previous years.

While the figures of the Health Department previously cited show the percentage to have increased very rapidly, the actual number of cases originating in Colorado was but slightly larger for the four years, while the total number of deaths from tuberculosis was considerably less; this, of course, effecting an increase in the proportion, but possessing no further significance. Thus in 1893 the total number of deaths from tuberculosis was reported as 435, of which 49 were specified as contracted in Colorado, establishing a percentage of 11.25. The next year the total number was 377, a diminution of 58, while the number contracted in Colorado was 51, an increase of but two cases for the entire year. It is obvious at once that the increase is entirely insignificant, yet the proportion is published as being 13.7 per cent., a gain of 2.5 per cent. in the deaths originating in Colorado for the year.

An analysis of the statistics for 1895 and 1896 gives practically the same results. The number of deaths in 1896 is but two more than for 1895, and but 17 more than for 1893, in spite of an increase in that time of 26,000 in the population, yet the percentage is much increased in 1896 on account of a diminution of 60 in the total tuberculous death-rate.

It is of much interest to note that the statistics for 1899, furnished by the Health Commissioner, were decidedly at variance with those previously reported, and serve to some extent as an official refutation of the asserted rapid increase of pulmonary tuberculosis in Colorado. Despite a material increase in the population of Denver since 1893, the number of cases specified as having developed in 1899 was but four more than in 1893, and the percentage of such cases to the total deaths from tuberculosis was but 9.9, about one-half that reported for the three previous years, and less than any proportion which has been determined since 1893. The compilation of these statistics was based upon the same official sources of information as in the previous years.

In the summer of 1901 the mortality statistics of consumption were reviewed upon the basis of the returns collected by the State Board of

Health rather than the Denver Health Department, during the sixteen months included between January, 1900, and May, 1901. An investigation conducted by different officials through the channels of another department and perhaps in accordance with other methods might be expected to disclose a difference in final results entailing a possible modification of previous conclusions. It is interesting to learn, therefore, that the proportion of deaths from consumption developed in the State to the total tuberculous death-rate for the sixteen months during which the statistics were collaborated was stated to be 13.32 per cent. This chanced to be the same proportion as was published by the Denver Health Department for 1894, and failed to indicate on the face of the returns any increase whatever in such deaths during a period of seven years. As a matter of fact, the proportion was about one-third less than that reported for 1897 and 1898.

Unfortunately, from 1901 to 1904 the Health Commissioner of the city of Denver preserved no record pertaining to cases of pulmonary tuberculosis contracted in Colorado. After diligent search it has been impossible to discover any data upon which to compile statistics of this nature during his tenure of office.

According to the official annual report of the statement of deaths for the city and county of Denver by the Health Department in 1905, there were 39 cases of pulmonary tuberculosis stated to have developed within the State, as compared with a total mortality rate from tuberculosis of 661, establishing a proportion of only 5.9 per cent., which is less than any year since the compilation of such statistics in 1893. In 1906, however, an increase was noted over the preceding year, there being 58 cases reported to have developed within the State as compared with a total death-rate from this disease of 634, making the percentage 9.1, which chances to be smaller than in 1893, or any succeeding year up to 1905.

Another aspect of the subject is the significance of an annual increase in the population, which was not formerly considered in the official computation of vital statistics in the State. While possibilities of error necessarily attend any effort to determine the relations of indigenous consumption, perhaps no method is as satisfactory in affording approximate conclusions as the proportion of such cases to the population. Accepting the figures of the Health Department relative to the population of Denver and the number of deaths annually from primary tuberculosis since 1893 as an eminently fair basis for analysis, the percentage of such deaths per 1000 inhabitants was found to vary but little from year to year, the proportion being less in 1894 than in 1893; in 1896, slightly less than in 1895, and in 1899, three per 10.000 people as compared with three and a fraction in 1893. Apropos of these results, attention is directed to the report of the Committee upon Tuberculosis, which stated that for the first eleven months of 1900, the only time during which statistics were compiled, the percentage of such deaths to the present population was three persons per 10,000 people. This coincided singularly with my analysis of death reports for previous years, being practically identical with results obtained for 1899 and 1893, being even less than in 1894, and presenting but trifling fluctuation in succeeding years. From this comparison it was seen that the Committee's report failed to demonstrate the slightest increase of indigenous consumption from the time the agitation received its inspiration.

As previously stated, there are no available statistics pertaining to this subject during 1901, 1902, 1903, and 1904.

The proportion of deaths from indigenous tuberculosis in 1905, according to the official report of the Denver Health Department, is less than two per 10,000 people; in 1906, a little over two for 10,000 people, in both years being less than any percentage previously obtained.

Still another phase of the subject is the relation of infantile tuberculosis mortality to the total deaths from consumption contracted in Colorado. An analysis of data obtained from the Denver Health Department showed that, of all persons reported to have died of tuberculosis originating within the State during a period of seven years, up to 1900, nearly one-fourth were children under four and five years of age, of whom 85 per cent. died of tuberculous meningitis. During the following year, out of a series of 76 cases, concerning which special detailed information was obtained, 27, or over one-third of the entire number, were under five years of age. Manifestly, in view of the special predisposition, such infantile cases, without qualifying explanation, should not be included as instances of death from indigenous pulmonary tuberculosis.

A similar consideration deserving mention is that of occupation. It is found, by reference to the report of the Tuberculosis Committee, that out of a total of 224 cases 49, or more than one-fifth, occurred among miners. The vast importance attaching to so large a proportion among this class, modifying as it does any superficial conclusions, is appreciated when one considers that the tuberculous element is subordinate to other pathologic changes, and occurs as a mere final development. It is suggested that these patients scarcely ever associate with consumptives, but exhibit a constant disregard of general hygienic laws which involve subsequent tissue changes insuring a favorable soil. Obviously, these cases should not be instanced as examples of the dangers of every-day infection.

As bearing directly upon this line of thought, the attention of the student is directed to the location, in the State, of reported indigenous cases. El Paso County, containing a greater relative proportion of consumptives than any other, and, therefore, likely to yield the largest percentage, presents the remarkably small number of six cases, or about of the whole. Gilpin County, with a much smaller population, among whom consumptives are exceedingly infrequent, the people being comprised largely of miners, offers a percentage nearly three times as great.

A factor of no inconsiderable importance, to which attention was called by me in 1897, is the entire absence of proof that cases reported as developing in Colorado were actually contracted here. It was contended that the mere fact of an individual exhibiting physical signs of tuberculosis less than one year after arrival is no evidence of its having originated in Colorado.

The arbitrary inclusion of such cases unavoidably implies a nonacceptance of the theory of a latent tuberculous process, and is opposed to the incontrovertible testimony adduced in recent years as to the extraordinary frequency of unsuspected tuberculous infection. Many Colorado physicians, from their daily experience, can testify concerning individuals apparently sound, with clear eye, bronzed cheek, and well-rounded proportions, yet victims of an incipient, if not active, infection. Is it not probable, among the large number of people coming