502 THE BRAIN. 



mate object, but only of the immediate stimulus upon which they depend. 

 All the emotions, and the expressions to which they give rise, are ner- 

 vous phenomena of this kind. The feelings of cheerfulness or depres- 

 sion, satisfaction, hilarity, or displeasure, are expressed, whenever they 

 reach a certain degree of intensity, by tears or laughter, by inarticulate 

 sounds, attitudes or movements of the body, which, though not inten- 

 tionally calculated to produce that effect, are at once understood by all 

 who see or hear them. Jn man, certain diseases of the brain induce a 

 condition in which the emotional phenomena are much more easily 

 excited than in health, either from an undue activity of the nervous 

 centre in which they are located, or from the .diminished influence 

 exerted over them by the cerebral hemispheres. In these instances, 

 the individual is moved to anger, laughter, or tears on the most trivial 

 occasions, and from causes which would not produce such an effect in a 

 condition of health ; the feelings thus expressed being quite uncontrol- 

 lable for the time, although the patient may be conscious that they have 

 no reasonable motive. 



The action of the tuber annulare, as the centre of the emotional im- 

 pulses, is no doubt closely connected with its influence over the attitude 

 and locomotion. The manner in which these two functions are performed, 

 even in man, takes a great share in the manifestation of the emotions, and 

 in many of the lower animals forms the principal means by which they 

 are expressed. The normal postures of the body and limbs and the 

 movements of progression, although they are still possible after de- 

 struction of the cerebral hemispheres and ganglia, are at once abolished, 

 according to Vulpian, if the tuber annulare be removed or extensively 

 injured. 



There is no doubt, also, that the other nervous faculties which have 

 been enumerated as connected with the tuber annulare come to an end 

 as soon as this organ is subjected to mutilation. With the destruction 

 of the tuber annulare, according to the general testimony of experi- 

 menters, all indications of sensibility and volition disappear, and the 

 animal body is reduced to the condition of a helpless and unconscious 

 machine, in which the functions of respiration and circulation, with cer- 

 tain other involuntary reflex phenomena, are the only remaining mani- 

 festations of nervous action. 



The Medulla Oblongata. 



The medulla oblongata is distinguished from the spinal cord, of which 

 it is a continuation, not only by its external form, but also by the dif- 

 ferent arrangement both of the bundles of nerve fibres and of the gray 

 substance in its interior. 



In the spinal cord, the anterior, middle, and posterior columns of 

 white substance all consist mainly of parallel fibres running in a longi- 

 tudinal direction ; while there is a narrow band of transverse fibres, the 

 white commissure, at the bottom of the anterior median fissure. In the 

 medulla oblongata, a much larger number of horizontal and oblique 



