Infrared radiations occupy the span between the visible spectrum and radio waves, and encompass wavelengths 780–400,000 nanometers, neither boundary being precisely delimited. All bodies above absolute zero in temperature are potential sources of infrared radiations; therefore, all organisms are continually exposed to them. About 60% of the Sun's rays are infrared. Water absorbs infrared radiations strongly, except for the band of transparency between 780 and 1400 nm. Since protoplasm contains much water, it absorbs infrared radiations readily. A large animal absorbs infrared radiations at its surface, only the span from 780 to 1400 nm penetrating as far as the blood vessels.