What, then, may be the protective part played by the chill? A chill is made up of intermittent contractions of all the external muscles of the body. This activity results in an increase of the body heat and in an anemia of the superficial parts of the body, so that less heat can be lost by radiation. By this means, therefore, the external portions of the body contribute measurably to the production of the beneficent and saving fever. It must be remembered that this power of adaptation is not peculiar to man alone, but that it is a quality shared by all living creatures. While the human body has been adapting itself for self-protection by producing a febrile reaction whereby to kill the invading organisms, the invaders on their side have been adapting themselves for a life struggle within the body of the host. In these mortal conflicts between invaders and host, therefore, the issue is often in doubt, and sometimes one and sometimes the other will emerge victorious. We must believe that a similar adaptive response exists in all parasitic infections--the cycles varying according to the stages in the development of the invaders. If the bacteria develop continuously, the fever is constant instead of intermittent, since the adequate stimulus is constantly present. Bacteriology has taught us that both heat and cold are fatal to pathogenic infections; for this reason either of the apparently contradictory methods of treatment may help, _i. e_., either hot or cold applications. It should be borne in mind, however, that we have to deal not only with the adult organisms, but with the spores also. The application of cold may keep the spores from developing, while heat may promote their development, and the course of the disease may vary, therefore, according to our choice of treatment. From this viewpoint, we can understand the intermittent temperature in a patient who is convalescing from an extreme infection, as peritonitis, pylephlebitis, multiple abscess of the liver, etc. In these conditions there may occur days of normal temperature, followed by an abrupt rise which will last for several days-- this in turn succeeded by another remittance. This cycle may be repeated several times, and on our hypothesis we may believe it is caused by the successive development to maturity of spores of varying ages. If these premises are sound, the wisdom of reducing the temperature in case of infection may well be questioned. On this mechanistic basis the emotions also may be explained as activations of the entire motor mechanism for fighting, for escaping, for copulating. * * * * * * * * * * * * * * * * * * * *