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* Stallion
* Stallion
−
* Increases in diameter during erection and [[Reproductive_Behaviour_-_Pre-copulatory_Behaviour_-_Anatomy_%26_Physiology#Penile_Protrusion|protrusion]].
+
* Increases in diameter during erection.
+
* '''Retractor penis muscle''' still relaxes during erection, but '''no sigmoid flexure'''.
+
* Engorgement with blood plays a significant role in the highly vascular penis.