The _bodily warmth_ was measured _thermoelectrically_. Following preliminary experiments in which gastric temperatures were measured by a thermic sound, we adopted the procedure of continuously registering _rectally_ the body temperature [Kerntemperatur]. Parallel with this, the recording of the _skin temperature_ was undertaken. The point of measurement was the skin of the back at the level of the fifth thoracic certebral process. The thermoelectrical measurements were controlled before, during, and after the experiments by thermometric tests of the cheek and rectal temperature. In severe cooling, _checking of the pulse_ is difficult. The pulse becomes weaker, the musculature become stiff, and shivering sets in. Auscultation during the experiment by means of a tube stethoscope fastened over the tip of the heart proved effective. The tubes were led out of the uniform and made possible the continuous _listening to the heart during the stay in the water_. _Electrocardiographic controls_ were not possible in the water. After removal from the water they were possible only in those cases in which, a too severe muscle shivering did not disturb the electrocardiograph records. The following _chemical studies_ were carried out: following up of the _blood sugar picture_ (continuous); the _sodium chloride picture_ in the serum; the _nonprotein nitrogen_ (_Rest-N_); the _alkali reserve_; the alkali reserve of the venous and arterial blood and _sedimentation rate_ (before and after the experiment). Besides this the general _blood condition_ and _viscosity_ were followed during the experiment, and before and after the experiment the _resistance_ of the red blood cells and the protein content of the blood plasma (this refractometrically) were measured. The following _urinalyses_ were made regularly: _sediment_, _albumen_, _sugar_, _sodium chloride_, _acetone_, _acetic acid_, as well as a qualitative _albumen_ determination. In part of the experiment lumbar and suboccipital punctures were made as well as corresponding spinal fluid studies. Among _physical_ and _therapeutic measures_ the following were tested: _a._ Rapid warming by means of a _hot_ bath. _b._ Warming by means of a _light cradle_. _c._ Warming in a heated _sleeping bag_. _d._ Vigorous _massage_ of the whole body. _e._ _Wrapping in covers._ _f._ _Diathermy of the heart._ In addition the following drugs were given: _Strophanthin_ i. v.; _Cardiaz_ 1 i. v. and i. c.; _Lobelin and Coramin_ i. v. and i. c. In other experiments alcohol or grape sugar was given. A part of the experiments was begun under _narcosis_ (8 cc. _Evipan_ i. v.). _III. The Clinical Picture of Cooling_