The so-called dis-ease germs may be found in the healthy body, but that body does not have the dis-ease merely because that germ is present. If, however, there is a subluxation which interferes with the transmission of mental impulses the tissues soon become pathological and proper environment is created for the development of the germ. Then this germ propagates and soon there is a large number present. These germs will, however, disappear as soon as the tissues become normal. In other words, when the incoördination is restored to coördination the germs disappear. Source of Communication There are two recognized principal sources of communicable dis-ease common to man, namely, man himself and the lower animals. It is interesting to note that most of the so-called communicable dis-eases are peculiar to man alone. They are not found in the lower animals except as they are communicated by man for experimental purposes. It is true that domesticated animals are more susceptible to dis-ease than wild animals. From the standpoint of hygiene there must be a distinction made between the source of infection and the media of conveyance. Man and animals are considered the main sources of infection. Environment is regarded a source of infection. It is maintained that water, food, air, and soul form a media for conveyance, but they are not considered sources of infection. Rosenau, one of the leading hygienists, states that “most of the microörganisms causing the communicable dis-eases of man are frail and soon die in our environment, as in the air, soil or water.” Notwithstanding this fact, some still maintain that these frail little germs cause dis-ease. Modes of Transfer Hygienists assert that germs are transmitted either by direct or indirect means. The vehicles of transmission may be man himself, animals, or anything that will carry the germs from one person to another. Price says, “The most frequent and demonstrated mode of infection is by direct contact of dis-ease with the healthy, of the persons surrounding the infected one, such as physicians, nurses, etc.” We must differentiate between the mode of transmission, or, as it is sometimes called, the mode of infection, and the channel of infection. The channel of infection is the passage through which the germs enter the body. In tuberculosis the channel of entrance might be the respiratory tract, through the skin, or by means of the digestive tract, while the mode of infection or mode of transfer might be by such means as milk or sputum.