BASAL GANGLIA OF THE ENCEPHALON. 609 



They are rather broader above than below and are about three-quarters of an 

 inch (19 mm.) in length. They are composed of longitudinal white fibres 

 connecting various parts with the cerebrum. Each crus is divided into a 

 superficial and a deep band, by a layer of gray substance called the locus 

 niger. The locus niger contains small, multipolar nerve-cells and abundant 

 pigmentary granules. The lower, or superficial band of the crus is called 

 the crusta. The deep band is called the tegmentum. The crusta consists 

 of white fibres only. In the tegmentum the fibres are mixed with masses 

 of gray matter. 



Pons Varolii. The pons Varolii, called the tuber annulare or the meso- 

 cephalon, is situated at the base of the brain, just above the medulla oblon- 

 gata. It is white externally and contains in its interior a large admixture 

 of gray matter. It presents both transverse and longitudinal white fibres. 

 Its transverse fibres connect the two halves of the cerebellum. Its longi- 

 tudinal fibres are connected below with the anterior pyramidal bodies and 

 the olivary bodies of the medulla oblongata, the lateral columns of the 

 cord and a certain portion of the posterior columns. The fibres are con- 

 nected above with the crura cerebri and pass to the brain. The super- 

 ficial transverse fibres are wanting in animals in which the cerebellum has 

 no lateral lobes. 



If the cerebral hemispheres, the olfactory ganglia, the optic lobes, the 

 corpora striata and the optic thalami be removed, the animal loses the spe- 

 cial senses of smell and sight and the intellectual faculties, there is a certain 

 degree of enfeeblement of the muscular system, but voluntary motion and 

 general sensibility are retained. As far as voluntary motion is concerned, 

 an animal operated upon in this way is in nearly the same condition as one 

 simply deprived of the cerebral hemispheres. There are no voluntary move- 

 ments which show any degree of intelligence, but the animal can stand, and 

 various consecutive movements are executed, which are different from the 

 simple reflex acts depending exclusively upon the spinal cord. The co-ordi- 

 nation of movements is perfect, unless the cerebellum be removed. As re- 

 gards general sensibility, an animal deprived of all the encephalic ganglia, 

 except the pons Varolii and the medulla oblongata, undoubtedly feels pain. 

 This has been demonstrated by Longet, Vulpian and others. In rabbits, rats 

 and other animals, after removal of the cerebrum, corpora striata and optic 

 thalami, pinching of the ear or foot is immediately followed by prolonged 

 and plaintive cries. Both Longet and Vulpian have insisted upon the char- 

 acter of these cries as indicating the actual perception of painful impressions, 

 and as very different from cries that are purely reflex, according to the ordi- 

 nary acceptation of this term. Longet alluded to the voluntary movements 

 and the cries observed in persons subjected to painful surgical operations, 

 when incompletely under the influence of an anaesthetic, concerning the 

 character of which there can be no doubt. He regarded the movements as 

 voluntary, and the cries as evidence of the acute perception of pain ; but it 

 is well known that such patients have no recollection of any painful impres- 

 sion, although they have apparently experienced great suffering. As far as 



