Recent investigations tend to prove more and more that tuberculosis is inherited in but rare cases; that inheritance is simply a predisposing factor, and that the real cause is infection. As an illustration of this, all have seen instances in which there had been apparently no cases in a family for ten or fifteen years, when from some cause one case develops, and this is soon followed by other cases in the same family. Whatever rôle heredity may play in these cases, this simply shows that the first case produced the infectious material which found a suitable soil in the other members of the family and developed a similar disease. The inheritance theory has been the source of much injury by causing members of the afflicted family to submit to the apparently inevitable instead of instituting measures for its prevention. The infectious product in tuberculosis is not the breath, as is so frequently believed by the laity, but simply the expectoration which comes from the diseased lungs or throat. When this is allowed to come in contact with clothing or other material in the room, it becomes dry and loads the atmosphere with a dust which contains the infectious bacillus, which may cause a similar disease in a person predisposed by heredity or sickness to this affection. The germ of tuberculosis is the seed, and the predisposed person the soil, and it requires a combination of both to develop the disease. To illustrate the necessity of suitable conditions for the development of plants--for it is now almost universally admitted that the germ of tuberculosis is a micro-organism which belongs to the vegetable kingdom--I remember some years ago, while in North Europe, seeing in a hothouse a plant which is here commonly known as the "four o'clock." The gardener in charge of the conservatory considered it a remarkable plant, but difficult to propagate, and stated that it was absolutely impossible to raise it out of doors. In this part of the world, however, we know that this plant grows so easily that once established in a garden it is difficult to keep it within limits. In both of the cases we have the same seed, the difference being only in the soil and the conditions favorable for its development. The absence of either the seed or the soil will absolutely prevent tuberculosis, and if the laws of hygiene are properly carried out, both in destroying the seed and in preventing the formation of a suitable soil, favorable effects will soon be shown.