On-Line Biology Book: The Endocrine System
Looks at the system's evolution, feedback mechanism, and other chemical messengers.
www.emc.maricopa.edu/faculty/farabee/BIOBK/BioBookENDOCR.html
HistoWeb: Endocrine System
Features a series of tissue samples from the pituitary, thyroid, and adrenal glands.
www.kumc.edu/instruction/medicine/anatomy/histoweb/endo/m_endo.htm