At birth, the rat spinal cord has 5% of the adult weight and 21% of the adult length. The ratio of weight to length, the 'thickness', more than doubled between 7 and 20 days of age and doubled again between 20 days and adulthood. The intact spinal cord can be removed from rats of any age within 1 min. After decapitation and partial dissection of the vertebral column at the sacral level, the spinal cord is ejected by means of hydraulic pressure from a syringe. Use of this method avoids prolonged dissection of the vertebral column with associated anoxia and trauma.