The origin, distribution, anastomoses and variations of the arteries of medulla oblongata were observed on 110 Chinese adult brains. The internal arteries and their territories were observed on 20 brains by artereography and clearing method (Spalteholz's technic). The results were as follows: The arteries of medulla oblongata could be divided into four groups according to their distribution. The arteries of the anteromedian and anterolateral groups arose from the anterior spinal artery, and also from the vertebral artery and basilar artery. The arteries of the lateral group contained a series of small arterial rami, which arose from the vertebral artery, posterior inferior cerebellar artery, anterior inferior cerebellar artery and basilar artery. The arteries of the posterior group arose from the posterior spinal artery and posterior inferior cerebellar artery. The arteries of each group branched and penetrated into the medulla, they ramify into fine branches, and the capillary network was formed. The internal anteromedian arteries supplied the hypoglossal nucleus, medial lemniseus etc. The internal anterolateral arteries supplied chiefly pyramidal tract. The internal posterior arteries supplied the gracile and cuneate nuclei. The internal lateral arteries supplied the rest of the areas which include reticular formation, dorsal nucleus of the vagus nerve etc.. The arterial supply of the medullary lateral area and the endartery were discussed.

The arteries of 5 human brainstems were injected by using a mixture of preparedchinese ink and gelatin.The capillary densities of 20 various nuclei and tracts inthe medulla oblongata were observed and measured in 300?m and 150?m serial trans-verse sections.The tracts are less vascularized than nuclei.The nuclei have been divided intohigh,medium and low three groups according to their capillary densities.The highdensity nuclei consist of accessory cuneate nucleus,inferior olivary nuclear complex,medial vestibular nucleus,nucleus cuneatus.The medium density nuclei are lateralreticular nucleus,nucleus supraspinalis,hypoglossal nucleus and nucleus gracilis.Thelow density nuclei are dorsal vagal nucleus,spinal trigeminal nucleus,nucleus ofsolitary tract.The pyramidal tract has the lowest density among the tracts observed.