Much oftener than is generally supposed the _kidneys_ are the seat of tuberculosis; and also the _suprarenal capsules_, whose functions are as yet entirely unknown, have in postmortem examinations been found to be tubercularly degenerated. In the diseases of the _bones_ and _joints_ tuberculosis forms an important part. Those infinitely small and weak tubercle-bacilli have the power to destroy the hard and firm substance of the bones, to soften it and change it to pus. Whole portions of bone may disappear in this way. Tuberculosis can also destroy parts of the _skin_. In this case it is called _Lupus_. Finally tuberculosis is found in the _generative organs_. Tubercular derangements are frequently met with in the _testicles_ of men, less often in the _ovaries_ of women. The well known children's disease _Scrofula_ is considered a preceding stage of tuberculosis by many physicians. This much is certain that Scrofula inclines to tuberculosis. Let us study the several forms of tuberculosis after this general synopsis; we will begin with pulmonary consumption. Pulmonary Consumption. Even before the discovery of the tubercle-bacillus by Koch, different scientists had claimed that pulmonary consumption was caused by the immigration of bacteria into the lungs, and several of them had found bacteria of that kind. But it remained for Koch to bring light upon the conjectures of other scientists, and he established the fact, that the bacillus discovered by him was the real generator of pulmonary consumption. Millions of these bacilli exist in the lungs of the diseased, and millions of them are thrown out with the sputum. If we take a very small quantity of this thrown out matter and examine it with a microscope, we will find a greater or smaller number of these tubercle bacilli. Of course the preparation to be microscopically examined must previously be colored with some coloring matter, otherwise it is very difficult, well nigh impossible, to detect the infinitely small bacilli. The method of coloring now generally in use consists in discoloring the preparation after the coloring has been completed, it is found that the bacilli tenaciously cling to the coloring matter, and in this way it is easy to recognize the tubercle-bacilli under the microscope. These bacilli are infinitely minute, they are 2/1000 to 8/1000 millimeters long, and about 5/100000 millimeters in width. Therefore it is absolutely impossible to recognize them with the naked eye. Generally they are somewhat bent, sometimes slightly nicked at one end. The temperature of boiling water destroys the vitality of the bacilli under all circumstances. Even a temperature of 70 deg. C. is able to lessen the efficacy of the bacilli. Unhappily this temperature is too high to be applied against the tubercle-bacilli in the human body without causing the most serious injury to it. Nevertheless it has been tried, we will speak of this later on.