BRAIN - Some Facts

• brain of total body weight (150 pound human) = 2%
  
  •Average brain width = 140 mm Average brain length = 167 mm
  
  •Average brain height = 93 mm
  
  •Intracranial contents by volume (1,700 ml, 100%):
  
  1.brain = 1,400 ml (80%);
  
  2.blood = 150 ml (10%);
  
  3.cerebrospinal fluid = 150 ml (10%) (from Rengachary, S.S. and Ellenbogen, R.G., editors, Principles of Neurosurgery, Edinburgh: Elsevier Mosby, 2005)
  
  4.Average number of neurons in the brain = 100 billion
  5.Number of neurons in brain (octopus) = 300 million (from How Animals See, S. Sinclair, 1985) Number of neurons in Aplysia nervous system = 18,000-20,000 Number of neurons in each segmental ganglia in the leech = 350 Volume of the brain of a locust = 6mm3

Source:- from The Neurobiology of the Insect Brain, Burrows, M., 1996