II. THE CHRONIC INFLAMMATORY DISEASES.

CHAPTER I.

TUBERCULOSIS.

TUBERCULOSIS is one of the most dreadful and, unfortunately, most common diseases of mankind. It affects alike the young and the old, the rich and the poor, the male and the female, the enlightened and the savage. Nor do its ravages cease with human beings, for it is common among animals, occurring with great frequency among cattle, less frequently among goats and hogs, and sometimes, though rarely, among sheep, horses, dogs, and cats.

Wild animals under natural conditions seem to escape the disease, but when caged and kept in zoological gardens even the most resistant of them-lions, tigers, etc.are said at times to succumb to it, while it is the most cominon cause of death among captive monkeys.

The disease is not even limited to mammals, but occurs in a somewhat modified form in birds, and, it is said, even at times affects reptiles.

It is not a disease of modern times, but one which has persisted through centuries; and though, before the advent of the microscope, not always clearly separated from cancer, it has not only left unmistakable signs of its existence in the early literature of medicine, but has also imprinted itself upon the statute-books of some countries, as Naples, where its ravages were great and the means taken for its prevention radical.

While the great men of the early days of pathology clearly saw that the time must come when the parasitic

nature of this disease would be proved, and some, as Klebs, Villemin, and Cohnheim, were "within an ace" of the discovery, it remained for Robert Koch to succeed in demonstrating and isolating the specific bacillus, now so well known, and to write so accurate a description of the organism and the lesions it produces as to render it almost unparalleled in medical literature.

The tubercle bacillus (Fig. 54) is a rod-shaped organ

ism with rounded ends and a slight curve, measuring from 1.5-3.5 in length and from 0.2-0.5 μ in breadth. It very commonly occurs in pairs, which may be associated end to end, but generally overlap somewhat and are not attached to each other. It is very common to observe a peculiar beaded appearance in organisms found in pus and sputum (Fig. 55), due to the contraction of fragmented protoplasm within the resisting capsule (?). By some these fragmentations are thought to be bacilli in the stage of sporulation. Koch originally held this view himself, but researches have not been able to substantiate the opinion, and at present the evidences pro

and con. point more strongly in the negative than in the positive direction.

The fragments do not look like the spores of any other organisms. When spores occur in the continuity of bacilli, they are generally discrete oval refracting bodies easily recognized. The fragments seen in the tubercle bacillus are irregular and biconcave instead of oval, have

FIG. 55. Tubercle bacillus in sputum (Fränkel and Pfeiffer).

ragged surfaces, and are without the refraction peculiar to the ordinary spore.

The spaces between the bacillary fragments cannot be made to stain like the spores of other species. Finally, all known spores resist heat more strongly than the fullydeveloped bacilli, but experimentation has shown that these degenerative forms are no more capable of resisting heat than the tubercle bacilli themselves.

The organism is not motile, and does not possess flagella.

The tubercle bacillus is peculiar in its reaction to the anilin dyes. It is rather difficult to stain, requiring that the dye used shall contain a mordant (Koch), but it is also very tenacious of the color once assumed, resisting the decolorizing power of strong mineral acids (Ehrlich).

These peculiarities delayed the discovery of the bacillus for a considerable time, but now that we are familiar with them they give us a most valuable diagnostic character, for with the exception of the bacillus of lepra no known bacillus reacts in exactly the same way.

Koch first stained the bacillus with an aqueous solution of a basic anilin dye to which some potassium hydrate was added, subsequently washing with water and counter-staining with vesuvin. Ehrlich subsequently modified Koch's method, showing that pure anilin was a better mordant than potassium hydrate, and that the use of a strong mineral acid would remove the color from everything but the tubercle bacillus. This modification of Koch's method given us by Ehrlich is at the present time acknowledged to be the best method of staining the bacillus. Many other methods have been suggested, all of them, perhaps, more convenient than. Ehrlich's, but none so good.

As being that most frequently performed by the physician, we will first describe the method of seeking the bacillus in sputum.

If one desires to be very exact in his examination, it may be well to have the patient cleanse the mouth thoroughly upon waking in the morning, and after the first fit of coughing expectorate into a clean widemouthed bottle. The object of this is to avoid the presence of fragments of food in the sputum.

The physician will secure a better result if the examination be made on the same day than if he wait a number of days, because if the bacilli are few they occur most plentifully in the small caseous flakes to be described farther on, which are easily found at first, but which break up and become part of a granular sediment that always forms in decomposed sputum.

The fresh sputum when held over a black surface generally shows a number of grayish-yellow, irregular, translucent granules somewhat smaller than the head of a pin. These consist principally of the caseous material

from tuberculous tissue, and are the most valuable part of the sputum for examination. One of the granules is picked up with a pointed match-stick and spread over the surface of a perfectly clean cover-glass. If no such fragment can be found, the purulent part is next best for examination. The mucus itself rarely contains bacilli when free from scraps of tissue and pus.

In cases in which this ordinary procedure fails to reveal bacilli whose presence is strongly indicated by the clinical signs, the exact method of searching for them is to partially digest the sputum with caustic potash, and then collect the solid matter with a centrifugal apparatus. If a very few bacilli are present in the sputum, this method will often secure them.

The material spread upon the cover-glasses should not be too small in amount. Of course a massive, thick layer will become opaque in staining, but should the layer spread be, as is often advised, "as thin as possible," there may be too few bacilli upon the glass to enable one to make a satisfactory diagnosis.

As usual, the material is allowed to dry thoroughly, and is then passed three times through the flame for purposes of fixation.

Ehrlich's Method, or the Koch-Ehrlich Method.-The cover-glasses thus prepared are floated, smeared side. down, upon, or immersed, smeared side up, in, a small dish of Ehrlich's anilin-water gentian-violet solution :

Anilin,

4,

Saturated alcoholic solution of gentian violet, II,
Water,

100,

and placed in an incubator or a paraffin oven, and kept for twenty-four hours at about the temperature of the body. When removed from the stain they are washed momentarily in water, and then alternately in 25-33 per cent. nitric acid and 60 per cent. alcohol, until the blue color of the gentian violet is almost entirely lost. It must be remembered that the action of the strong acid