At La Bourboule (France), arsenic and molybdenum are contained in high concentrations in the watering place. So, we have applied thermal neutron activation analysis to determine arsenic and molybdenum amplitudes after the treatments in some organs for the first time. Their variations are determined in blood versus time. Contamination by experimental materials are reduced or evaluated to take them into account in the results. It appears that rabbits are better standards than rats to make preliminary studies with animals. These experiments have been completed with studies on man. After drinking, there is a specific accumulation of arsenic in breaths while, after aerotherapeutics, it happens in trachea. Our measures indicate minima in blood concentrations of arsenic and molybdenum at the tenth day of thermal spring treatment; there are maxima in urines at the same time. The overall radiochemical neutron activation analysis and gamma ray high resolution spectrometry appears as a unique and powerful procedure to resolve the difficult biomedical problems.