ORDER OF SUCCESSION OF SOME OF THE COLD-WEATHER DISEASES.

I have proved that in Michigan the rise and fall of sickness from pneumonia follow quantitatively the fall and rise of the atmospheric temperature. This is apparent from a diagram (No. 4) which I present. I have shown by diagram (No. 3) that the rise and fall in the sickness from bronchitis, in Michigan, follow the fall and rise of the atmospheric temperature, although not so precisely quantitatively as is the case with pneumonia. By examining the evidence in these two diagrams, it may be seen that throughout the year an average of about forty per centum of the weekly reports stated that pneumonia was under observation, while an average of about sixty per centum of the reports stated that bronchitis was observed. It follows that among persons throughout the State exposed to the same atmospheric temperature, many more are taken sick with bronchitis than with pneumonia. It may also be seen that, as the cold weather approaches in the autumn, bronchitis increases more rapidly than pneumonia, also that it lingers longer in the spring months than does pneumonia. All these facts harmonize if we suppose that a less exposure to low temperature is ordinarily required to produce bronchitis than to produce pneumonia.

In Michigan the sickness from influenza, tonsillitis, croup, diphtheria and scarlet fever, follows more or less closely the fluctuations of atmospheric temperature. It seems necessary to explain how it is possible for a cold atmosphere to cause in one person ínfluenza, in another tonsillitis, in another croup, while in others it favors the contraction of a contagious disease like scarlet fever.* It is probable, however, that the explanation would have been easy long ago except for a misapprehension of one of the principal facts. It has generally been stated that when these diseases were favored by a cold atmosphere, the air was not only cold but damp; and just how cold alone could do so much, or how dampness could favor the production of one of these diseases, has never been explained, notwithstanding the fact that dampness renders the cold more apparent and perhaps more effective. But the fact which has been lost sight of is that cold air is always dry air, absolutely; it is only the relative humidity or percentage of saturation of the air that is great when the air is cold. This is made plain by the study of any table of the absolute humidity showing saturation of air at different temperatures; thus a cubic foot of air at zero Fahrenheit cannot contain more than one-half grain of vapor of water; at 32° F. it cannot contain more than two grains; while at 70° it may contain eight grains, and at 98° F., which is near the temperature of the air passages, each cubic foot of air may contain 18.69 grains of vapor. The influence of cold dry air in the production of "chapped" hands has probably been noticed by most persons, and the stopping up of the nose by drying must have been often observed early in the occurrence of common colds, as also the dry cough which so commonly calls for some medicine to "loosen the cough." But the drying effects of the inhalation of cold air can best be understood by reflecting that each cubic foot of air inhaled at zero F. can contain only one-half a grain of vapor, while when exhaled it is nearly saturated at a temperature of about 98° F., and therefore contains about 18.69 grains of water, about 18 grains of which has been abstracted from the air passages.

Coryza. Thus, cold air falling upon susceptible nasal surfaces tends to produce an abnormal dryness, which may go so far as to cause the "stopping up" of the nose, which may be followed by suppuration. In my opinion a common cold or coryza may thus be caused.

Influenza.-In some persons, under some circumstances, the nasal surfaces may not be susceptible to drying, that is to say, fluids may be supplied in increased quantity to

* In a paper entitled "Some of the Cold-weather Communicable Diseases," published in the Transactions of the Michigan State Medical Society for 1887, I have shown that the curves for scarlet fever, diphtheria and smallpox follow the curve for temperature.

meet the increased demand by the cold dry air, in which case the constant evaporation of the fluids will lead to an abnormal local accumulation of the non-volatile salts of the blood, such as sodium chloride, which is an irritant; and what is termed influenza may then arise. The close relations of influenza and atmospheric temperature are shown in the diagram (No. 1) which I submit herewith. It may be seen that influenza increases promptly in the summer and autumn, as soon as cold weather begins-more promptly than bronchitis or pneumonia does. This order of succession might be expected if these diseases are all caused in the manner pointed out in this paper; but it may, in part at least, be due to the shorter average duration of influenza.

Bronchitis.-The effects which the inhalation of cold dry air have upon the bronchial surfaces will depend greatly upon how the upper air passages respond to the increased demand for fluids; because if they do not supply the moisture the bronchial surfaces will certainly have to sustain an increased demand, in which case, as the phrase is among the common people, a "cold in the head" may then "settle on the lungs," and the person may have bronchitis. The bronchitis which results from the inhalation of cold dry air may be of that sort (like a cold in the head) characterized by an abnormal deficiency of the fluids, at least in the beginning of the disease, or it may be of that sort (like influenza) which is characterized by an excess of fluids, in which case, if the exposure is continued, the evaporation which results from the inhalation of air unusually cold and dry necessarily leads to the abnormal increase in that fluid of the non-volatile salts of the blood.

Pneumonia.-Bronchitis not infrequently precedes pneumonia. The most distinctive feature of lobar pneumonia is the exudation. Certainly the causation of pneumonia is not explained until the manner in which the exudation is caused has been made plain. In papers on the causation of pneumonia I have elsewhere pointed out how such an exudation should be expected to result, in accordance with known laws of osmosis, from long-continued exposure to the inhalation of cold dry air. Since 1850, when Dr. Redtenbacher published his observations, * it has been known that during the onward progress of pneumonia chloride of sodium is absent from the urine; and since 1852 it has been known, through the researches of Lionel Smith Beale, † of London, England, that the chloride of sodium which then disappears from the urine of a pneumonia patient, may be found in the sputa and in the solidified lung. I have shown that during the inhalation of cold dry air the quantity of fluid which passes out from the blood vessels into the air cells must be increased in order to meet the increased demand, and that through the increased evaporation an increasing quantity of the non-volatile salts of the blood may accumulate in the air cells. In connection with the foregoing I have also pointed out that as soon as the proportion of sodium chloride reaches about three or four per centum of the fluid in the air cells, the albuminous constituents of the blood should begin to pass out into the air cells. And thus the chain of explanation of how the exudation which occurs in croupous pneumonia is caused, seems to have been completed.

* Zeitschrift der k. k. Gesellschaft der Aerzte zu Wien, Aug. 1850.

† Vol. xxxv, Medico-Chirurgical Transactions, published by the Royal Medical and Chirurgical Society, London.

Transactions of the American Climatological Association, May 10, 11, 1886, pp. 226–233. Also, Proceedings of Michigan State Board of Health, Oct. 1886, pp. 7–11.

"But a substance like albumen, which will not pass out by exosmosis toward pure water, may traverse a membrane which is in contact with a solution of salt. This has been shown to be the case with the shell membrane of the fowl's egg, which, if immersed in a watery solution containing from three to four per centum of sodium chloride, will allow the escape of a small proportion of albumen. Furthermore, if a mixed solution of albumen and salt be placed in a dialysing

The law of osmosis, in accordance with which albuminous exudations occur whenever the fluid exterior to the blood vessels contains about four per centum of sodium chloride, probably applies, as a rule, to exudations throughout the air passages, and so I will not repeat it in connection with coryza, influenza, tonsillitis, croup and bronchitis. Indeed, the law probably applies in all diseases and throughout the human body; but it seems probable that there are other conditions which favor the exudation of the albuminous constituents of the blood, such conditions, for instance, as cause a breaking down or change in the albuminous constituents themselves, variation in the blood pressure through variations in the atmospheric pressure; and it is not difficult to see that blood pressure may be increased locally, as, for instance, through disturbed action of the heart, and, finally, an important factor in the causation of pneumonia and of exudation throughout the air passages, is undoubtedly the more or less complete paralysis of parts directly exposed to unusual cold, which may subsequently occur on their being subjected to warmth.

Bearing upon the subject of the influence of atmospheric pressure in favoring pneumonia, I submit a diagram (No. 7), which shows that in Michigan the curve for the average daily range of atmospheric pressure coincides very nearly with the reversed curve for the temperature, and that the sickness from pneumonia follows it somewhat closely, but not as closely as it does the temperature, perhaps, however, because the statistics relative to pressure do not cover sufficient time to obtain a correct average.

My researches appear to prove that pneumonia, whether croupous or catarrhal, seems to be controlled by the atmospheric temperature. It, therefore, seems true, as many have long believed, that for both forms the causation is similar. From my standpoint it seems possible that in the catarrhal form the sodium chloride in the fluid which moistens the air cells, does not reach or much exceed the three or four per centum, which is required in order that the ordinary albuminous constituents of the blood should begin to pass out into the air cells, as it does in croupous pneumonia. It also seems possible that lobar pneumonia may require for its production that partial paralysis which results from the experience of a warm atmosphere immediately following exposure to cold (such an effect as is seen in the flushed cheek of a person brought into a warm room from extreme cold outer air), in which case the exudation should occur in just that part of the lungs supplied by the nerve influenced by the cold, because the walls of the blood vessels of just that part should be relaxed. The chill may result from such a disturbance of the nervous equilibrium, and be in the nature of an attempt to regain control of the relaxed blood vessels.

Elsewhere* I have shown-and it may be seen by diagrams 8 and 9-that a few communicable diseases, which, as a rule, gain access to the body through the air passages, are quantitatively related to the atmospheric temperature, almost invariably rising after the temperature falls, and falling after the temperature rises. The explanation has seemed to me to be that those exudations which result from the inhalation of air colder than usual supply a nidus for the reception and reproduction of the specific contagia of scarlet fever, smallpox, etc.

Inasmuch as diseases known to be contagious follow so exactly the fluctuations of atmospheric temperature that pneumonia is also controlled by the temperature, is no proof of the non-contagiousness of pneumonia; but all, or nearly all, of the phenomena

apparatus, the salt alone will at first pass outward, leaving the albumen; but after the exterior liquid has become perceptibly saline, the albumen also begins to pass in an appreciable quantity." John C. Dalton, "Treatise on Human Physiology for use of Students and Practitioners," etc., Philadelphia, 1875, p. 363.

* "Some of the Cold-weather Communicable Diseases," in Transactions of the Michigan State Medical Society, 1887.

of pneumonia are now accounted for without reference to a special contagium, and the same can be said of bronchitis, influenza and the other diseases of the upper air passages.

BEARING UPON DIET AND TREATMENT.

If, as I believe, nearly all of the diseases of the air passages, and some contagious diseases which gain entrance to the body through the air passages, are associated with unusual evaporation of fluids from their surfaces, and the accumulation there of the non-volatile salts of the blood which act as irritants, and which, when in sufficient quantity, cause the exudation of the albuminous constituents of the blood, these facts have an important bearing upon the subject of diet best adapted to freedom from these two classes of diseases; for it is obvious that in a person whose blood is strongly saturated with sodium chloride or other fixed salt, the exudations may be quite different from those in a person whose blood is only scantily supplied with fixed salts.

If these views are found to be correct-namely, that trouble comes from the accumulation of the non-volatile salts in the air passages-they may help to explain why in practice a volatile salt, like ammonia, has sometimes been preferred to a salt of a fixed alkali, and why such a volatile substance as carbonate of ammonia has been preferred by some as even more satisfactory than the chloride of ammonium in the treatment of certain acute affections of the air passages.

The importance of ascertaining the controlling causes of this large class of diseases seems to warrant analyses of the fluids transuded in influenza and in bronchitis, and such other experiments by those who have opportunity as shall prove or disprove the views here set forth.

PREDISPOSING CAUSES-HYPERINOSIS AND PNEUMONIA.

Chemically, fibrin is oxidized albumen. It should not, therefore, be difficult to infer the direction in which we must search for the causation of hyperinosis, namely, in the direction of the causation of abnormal oxidation of the blood. This condition of the blood occurs in pneumonia, in rheumatism and in certain other diseases, and is believed by some to constitute an inflammatory condition of the blood-a tendency toward inflammation. Thus, in Aitken's "Science and Practice of Medicine," Vol. II, p. 508, Dr. Parkes is quoted as saying: "That hyperinosis is really anterior in pneumonia as in rheumatism, must, in spite of the opinion of Virchow, be considered likely from experiments, among others, of Prof. Naumann, of Bonn." It is conceivable that abnormal oxidation of the blood serum may result from an abnormal proportion or activity of the red blood corpuscles. In the same paragraph quotation from Dr. Parkes it is said: "It is well known how frequently the liver is affected in pneumonia, so that some amount of jaundice is not at all uncommon, and sometimes bile pigment appears in the pneumonic sputa. I have also found in some cases evidence of liver affection for some time before the lung disease, especially the so called torpor with deficient biliary flow." Whenever the production of red corpuscles continues at the normal rate, and they are not destroyed in the liver as fast as they normally are, it would seem that their accumulation may favor excessive oxidation of the albuminous constituents of the blood serum, in a condition described by the word hyperinosis. But it is still more conceivable that abnormal oxidation of the blood serum may result from the inhalation of oxygen in greater than normal amount, or in a condition of unusual activity, and ozone is oxygen in such an active condition. Furthermore, the curve for the rise and fall of atmospheric ozone is, in Michigan at least, almost precisely the curve for the rise and fall of pneumonia. (It is probable, however, that the quantity of residual atmospheric ozone is controlled by the atmospheric temperature.) It may be added, also, that the

Aitken's "Practice," Vol. II, p. 508.

late Dr. Henry Day, of London, England, claimed that his experiments with dogs proved that the inhalation of ozone caused bronchitis, and in larger quantities, pneumonia.

While, therefore, I do not claim that atmospheric ozone is the sole cause of pneumonia, it seems quite probable that it may be a cause of hyperinosis, which is apparently a predisposing cause of pneumonia and of other diseases. It seems reasonable to believe also that an exudate, which under other conditions would be readily reabsorbed or taken away by the lymphatics as rapidly as formed may, under the influence of the abnormal oxidizing action of ozone, become too insoluble to be thus disposed of, and consequently accumulate as the fibrinous exudate in pneumonia, in pleuritis, in croup, etc., and also serve as a nidus for any contagium inhaled.

In Michigan the curves for sickness and for deaths from pulmonary consumption seem to follow irregularly the inverted temperature curve, about one to three months later in time. Consumption thus seems to be influenced by the same meteorological conditions as is pneumonia. In this connection and in connection with what has been said as to the difficult removal of oxidized exudates, it is worthy of notice that Dr. H. F. Formad, of Philadelphia, has claimed that a structural condition predisposing to consumption is abnormally few and narrow lymph spaces in the connective tissues.* All of these alleged facts seem to be in harmony with what I have suggested as to the fibrinous nidus being the controlling cause of certain communicable diseases which enter through the air passages.

Pulmonary Consumption.-But with a contagium which enters the body, but not through the air passages, if it is capable of entering the general circulation it is probably capable of passing from the circulation to any exudate; so the formation and especially the retention of such an exudate in the lungs and air passages would be expected to supply the conditions for the rapid multiplication of any such contagium. In this connection I submit a diagram (No. 11) showing that in Michigan the sickness reported from pulmonary consumption follows the inverted temperature curve with considerable regularity, except that in the summer and autumn months it is separated from the temperature by a shorter period of time than it is in the winter and spring. The sickness under observation (which includes old cases) will be lessened by the deaths, and this should be especially noticed when the conditions favoring deaths do not also equally favor the production of new cases, as may be the fact on the approach of warm weather. However it may be, the curves for deaths need to be studied. I regret that the deaths in Michigan are not all reported, and the omissions are greater in the earlier months of each year; but in a diagram which I have prepared it may be seen that after making a correction for the omissions (estimated by comparison with census statistics) the curve for deaths is somewhat similar to the curve representing sickness. Relative to deaths, however, more satisfactory evidence is presented to you in the diagram (No. 10), representing the relation of the deaths from phthisis in London, England, during thirty years, from which it is plain that the curve for deaths from phthisis follows the inverted temperature curve with great regularity.

Returning now to the curve for sickness from consumption in Michigan (Diagram 11): If in the summer months the reduction of the sickness by reason of the deaths is as great as the reduction by reason of the warmer weather, the curve for sickness should show, as it does, a more than average decrease, in fact, a double decrease after

"Tuberculosis usually ensues when a simple inflammation is set up by any kind of injury, in animals with the structural peculiarities that I have described; but tuberculosis cannot be produced in animals which do not have this structural peculiarity, so far as my experiments show, unless the injury is inflicted upon serous membranes."-Journal of American Medical Association, Vol. II, p. 148.