Pacinian corpuscles are dynamic mechanoreceptors which accelerate movement during reflexes. Pacinian corpuscles act as very rapidly adapting mechanoreceptors. Bulbous corpuscles are also known as Ruffini corpuscles, or type II cutaneous mechanoreceptors. Light touch is transduced by the encapsulated endings known as tactile (Meissner) corpuscles. Stretching of the skin is transduced by stretch receptors known as bulbous corpuscles. The foreskin contains Meissner's corpuscles, which are nerve endings involved in fine-touch sensitivity. No Meissner's corpuscles and few organized nerve endings are present. The lips are also protected by specialized sensory cells called Meissner's corpuscles. Thomson suggested that atoms were divisible, and that the corpuscles were their building blocks. He thus concluded that atoms were divisible, and that the corpuscles were their building blocks. The region has a high density of nerve endings known as the corpuscles of Herbst. In vertebrates, this is accomplished by Ruffini endings and Pacinian corpuscles. The exact purpose of the keratinization of Hassall's corpuscles remains unknown. Pacinian corpuscles determine gross touch and distinguish rough and soft substances. Bulbous corpuscles react slowly and respond to sustained skin stretch.