130 Instinct and Intelligence 



show as sharply-cut fissures; the intervening 

 brain-substance is known as forming its con- 

 volutions. The pattern which the principal 

 sulci and convolutions of the brain assume in 

 the various orders of mammals is fairly con- 

 stant, so that anatomists, by inspecting the sur- 

 face of a series of brains, is able to state to 

 which class of animals each of them has be- 

 longed. 



The upper and lateral surfaces of a dog's 

 brain present several well-defined infoldings of 

 its cortex ; on the base of the brain a part of its 

 basal ganglia is conspicuous; they project into 

 the lateral ventricles or space which exists in 

 the brains of all the higher orders of animals. 

 These ganglia, in fact, as in the lower classes 

 of animals, constitute the receiving central and 

 dispatching centres for incoming and outgoing 

 streams of energy, derived from the animal's 

 nervous sensory organs. 



After a dog has been completely anaesthetised 

 if certain areas of his cerebral cortex are stimu- 

 lated by an electric current, contractions of 

 definite groups of muscles of his body and limbs 

 take place. At one spot excitation of the 



