The<unk>  (frequently abbreviated as "HERS") is a proliferation of<unk>  cells located at the cervical loop of the enamel organ in a developing tooth.<unk>  initates the formation of dentin in the<unk>  of a tooth by causing the differentiation of odontoblasts from the dental papilla.  The<unk><unk>  eventually disintegrates, but residual pieces that do not completely disappear are seen as<unk>  cell rests of Malassez (ERM).<unk>  was not discovered in any mammalian species. Instead this<unk>  structure was discovered by Oskar<unk>  in 1874 in an amphibian. While in mammalian the HERS is rather a transient structure in amphibians it is more or less a permanent one. Here the<unk>  epithelium does not fenestrate like in mammalians. Within vertebrates 3 distinct stages of HERS development can be observed.
Hertwig's epithelial root sheath
Inner cell mass
Rathke's pouch
Olfactory epithelium
Junctional epithelium
Golgi tendon organ
Mucogingival junction
Germ layer