altogether unreasonable. It is regrettable that the protection of public health often necessitates the imposition of annoying and impeding restrictions that add to the cares of those whose lives are burdened with a serious disease. But what other course can we follow?

Tuberculosis, unfortunately, is infectious, and the best way to escape it is to shun the virus to which it is due and to avoid the source from which this virus is expelled. A policy that attempts to characterize as anything better than extremely dangerous the sources from which the essentially necessary causative agent of an infectious disease that is responsible for more than 10 per cent of all deaths is derived is very shortsighted. To refrain through motives of sympathy and charity from imposing various irksome and disadvantageous restrictions on those who are the unhappy victims of tuberculosis is equivalent to making sentiment an apology for the sacrifice of thousands of healthy persons in the present generation and millions in coming generations to a deadly plague.

When we actually realize the truth about tuberculosis and the number of victims that it claims we are in a better state of mind to join those who may be classed as afflicted with phthisiophobia than those who seek to belittle the dangerous character of tuberculous individuals for their fellow-creatures. During 1908, according to the most reliable figures obtainable, 160,000 human lives were prematurely ended by tuberculosis in the United States alone, and this enormous number does not include the deaths hastened by tuberculosis but chargeable to other immediate causes. Every one of these deaths was due to infectious material that had its origin within and was expelled from the bodies of tuberculous persons and animals.

There is too strong a tendency at the present time to characterize the careful consumptive as not dangerous to those with whom he is associated. No doubt he is a less danger than the careless consumptive, but we can not afford to teach that the degree of danger he represents is so small that we can safely afford to disregard it. We must bear in mind that the infectious disease with which he is affected, according to the figures presented at the recent International Congress on Tuberculosis by the United States Public Health and MarineHospital Service, destroyed 60,000 more lives in the United States last year alone than yellow fever destroyed in the United States during the whole of the last century.

The writer, whose knowledge of tuberculosis and its mode of transmission is derived from years of special study, attempted recently to protect his environment from infection with such particles of material, emanating from his own body, in which tubercle bacilli are commonly expelled from the bodies of persons affected with pulmonary or laryngeal tuberculosis. The conclusions drawn from this attempt are in accord with the investigations of Bartel and

Spieler, who liberated a number of guinea pigs in the dwelling of an intelligent, careful consumptive, who used a sputum flask to prevent spreading tubercle bacilli with the material he expectorated, and who, no doubt, under the direction of the investigators, took every reasonable precaution to protect his environment from becoming infected with tubercle bacilli expelled from his body. A portion of the guinea pigs contracted tuberculosis from this exposure, thus proving that the environment of even a careful consumptive is by no means free from active, virulent tubercle bacilli, and therefore is not safe.

As some objection may be made to the quoted experiment because of the reputed high susceptibility to tuberculosis of the animals used, attention is called to the fact that guinea pigs have been repeatedly shown at the Experiment Station of the Bureau of Animal Industry to be quite resistant to tuberculous infection unless the tubercle bacilli are injected directly into their bodies. In one experiment c d 7 healthy cattle and 98 guinea pigs were exposed simultaneously for a period of about half a year to 3 tuberculous cows. The exposure was so severe that 6 of the 7 cattle contracted tuberculosis, but 97 of the guinea pigs remained healthy.

b

A clear conception of the danger to which public health is exposed through the use of food products derived from tuberculous dairy herds requires that we should have some knowledge of the following special subjects, which will be discussed in order: (1) The character of tuberculosis as a disease of cattle; (2) the manner in which tubercle bacilli are expelled by tuberculous cattle; (3) the general appearance of tuberculous cattle that expel tubercle bacilli; (4) how tubercle bacilli from cattle get into milk and other dairy products; (5) the virulence and vitality of tubercle bacilli in dairy products; (6) the proportion of tuberculous cows among those in use for dairy purposes; and (7) the frequency with which dairy products have been proven under existing conditions to contain tubercle bacilli.

THE CHARACTER OF TUBERCULOSIS AS A DISEASE OF CATTLE.

Tuberculosis of cattle, as of persons, may be acute and rapidly progressive and run its course quickly from infection to death. This is rare, however. As a rule it is insidious, chronic, and slowly progressive, and the bodies of its victims are able to adapt or adjust

"Review in Hygienisches Centralblatt, Vol. IV, No. 11, p. 322, 1908. (Reference from the Wiener Klinische Wochenschrift, vol. 20, No. 38, pp. 1144-1150, 1907.)

Twentieth Animal Report, Bureau of Animal Industry, 1903, pp. 61-68. Twenty-first Annual Report, Bureau of Animal Industry, 1904, pp. 44-65. d Bulletin 86, Bureau of Animal Industry, 1906, pp. 7-9.

themselves to the gradually increasing destructive changes that it causes until quite extensive harm has been done or vitally important organs have become seriously involved. The result is that the disease

FIG. 7.-Section of a tuberculous lung from a cow, showing cavity formation and thickening of interlobular connective tissue. The cavities have dense connective-tissue walls and represent the closest approach in the lungs of cattle to the cavity formation that is of common occurrence in the tuberculous lungs of persons.

may be present in the body a long time without external manifestations of its existence. It may attack any part of the body singly

and remain confined to it, or it may attack several or many parts simultaneously or successively. Its favorite location in the bodies of cattle, as in those of persons, is the lung.

The tuberculous lungs of cattle do not show the decided cavity formation seen in human tuberculous lungs, but cavities in direct communication with the exterior of the body through bronchial tubes and more or less completely surrounded by heavy, dense, connectivetissue walls are common. The dissimilarity of the lesions in the lungs of persons and in those of cattle are no doubt the result of normal anatomical differences. The lungs of cattle, unlike those of persons, have very decidedly outlined lobules, which are bounded by webs of loose, elastic connective tissue. This tissue is so abundant that it admits of a serous and cellular infiltration through which the lobules may be separated from each other as much as one-sixteenth or even one-eighth of an inch, and consequently not only pulmonary tuberculosis but most lung diseases of cattle and other ruminants have a special, distinct character.

Figure 7, which is from a photograph of a section of a tuberculous lung of a cow, shows the character of cavity formation and the thickening of interlobular connective tissue as they occur in cattle. Even where the interlobular tissue is not greatly thickened by the tuberculous processes it can be seen in the form of fine lines bordering the individual lobules.

Tuberculosis is more effectually concealed in the bodies of cattle than in those of persons, and we all know how long a diagnosis with persons may remain in doubt. Perception, or the faculty to receive impressions, is keenest where the nervous system has the highest development. Persons, though their perception of pain is much keener than that of lower animals, complain little during the earlier stages of tuberculosis, because, we may assume, they experience little pain or distress during those stages. Cattle, with their lower perception and comparatively insignificant means to express suffering, give no indication of any pain and distress that tuberculosis may cause them.

The frequency with which tuberculous subjects cough depends largely upon perception, or sensations in their lungs and throats that prompt them to cough. Cattle shown on autopsy to have extensive, advanced, tuberculous lesions of the lungs, though observed long periods of time before their death, were found to cough only a little more frequently than cattle shown on autopsy to have healthy lungs. When tuberculous cattle cough it is usually a single, accelerated expiratory effort, or at most two or three such efforts in succession, which are sufficient to raise the material that has accumulated in their larger air passages far enough into their mouths to be swallowed. Expectoration, which is common with persons, does not occur in cattle, and paroxysms of sustained coughing, also common with persons, are

very rare in cattle and occur only during the last stages of pulmonary tuberculosis.

The bodies of all animals are stronger and more capable, as a whole as well as in their individual parts, than the ordinary vicissitudes of life require them to be. The difference between the actual strength and capability and that ordinarily required is known as the factor of safety. The rarely interrupted, placid routine of a cow's life enables her to derive full benefits from the factors of safety in her body when she becomes affected with a slow, chronic disease, such as tuberculosis, the lesions of which are circumscribed in the sense that they do not

lymph glands of the throat, as is shown by the position of the head. The glands are so much enlarged that, through pressure on the larynx, they greatly narrow the orifice through which air reaches the lung; and yet the visible bodily condition of the cow has remained very good, and is better than that of most dairy cows.

seriously affect parts of the body remote from those in which they are located; hence the factors of safety greatly help to prevent tuberculous disease in the bodies of cows from showing itself by external symptoms. An example of this is seen in figure 8, which shows a cow affected with advanced tuberculosis.

The tuberculous disease of the cow represented in the picture is partly located in the glands of her throat; the enlarged glands press on and narrow the passage through which air reaches her lung to such an extent that she almost dies of suffocation when she is driven a short distance at a moderately fast walk. The general condition of the cow shows that the opening through which the air she breathes

27661-10-2