750 THE RESPIRATORY CENTER AND NERVES. 



establishes a connection among the various centers for the reflexes, in the 

 spinal cord. When Owsjannikow divided the medulla 6 mm. above the 

 calamus scriptorius (in rabbits) , the general reflexes of the body, in which 

 the anterior and the posterior extremities took part, persisted. When 

 the section was made i mm. lower, only partial, local reflexes usually 

 appeared. The center extends upward to a little above the lower third 

 of the medulla. 



In the frog the medulla contains the sole center for movement from 

 place to place. Division of this abolishes such movement in response to 

 external irritation and only simple reflexes remain, but no reflex move- 

 ment, such as jumping, crawling, swimming. 



Pathological. The medulla oblongata *may be the seat of a typical disease 

 designated bulbar paralysis, or glossopharyngolabial paralysis, attended with 

 progressive paralysis of the bulbar (bulbus rhachiticus, medulla oblongata) nuclei 

 of various cerebral nerves, which often represent the motor segments of important 

 reflex mechanisms. From the latter point of view the clinical picture deserves 

 consideration. Generally, the disorder begins with paralysis of the tongue, at- 

 tended with fibrillary twitching, in consequence of which speech, the formation 

 of the bolus, and swallowing in the mouth are rendered difficult. The secretion of 

 an extremely viscous saliva indicates an inability to secrete a watery saliva by 

 reason of paralysis of the facial nerve. Further, swallowing is rendered difficult 

 or even impossible in consequence of paralysis of the pharynx and the palate. 

 As a result of the latter the formation of consonants between the tongue and 

 the soft palate is interfered with; speech, further, becomes nasal; and often 

 especially fluid articles of food enter the nares on efforts at swallowing. Then, the 

 facial branches for the lips become paralyzed. The mimetic expression of the 

 mouth is extremely characteristic, "as if frozen stiff," and, at the same time, 

 in consequence of horizontal enlargement of the opening of the mouth (as the 

 orbicularis oris especially is paralyzed), marked by a lacrimose appearance. 

 Later on, speech becomes more greatly interfered with. When the disorder is 

 marked, all of the muscles of the face are paralyzed. Under such circumstances, 

 the laryngeal muscles are not rarely paralyzed, so that phonation is abolished, 

 and the ready entrance of fluids into the larynx is favored. The enormous re- 

 tardation of the pulse-beat often present indicates irritation of the cardiac in- 

 hibitory fibers, derived from the accessory nerve. If, later on, attacks of dyspnea 

 occur, such as have been observed after paralysis of the recurrent nerve, or such 

 as are constant after section of the pulmonary branches of the vagi, death may 

 take place suddenly amid signs of asphyxia if the attacks become more severe 

 and more frequent. Rarely, the clinical picture is complicated by paralysis of 

 the muscles of mastication (in consequence of paralysis of the motor portion of 

 the fifth nerve), contraction of the pupils (in consequence of paralysis of the 

 dilator-center) and paralysis of the abducens nerve. 



THE RESPIRATORY CENTER AND THE INNERVATION OF THE 

 RESPIRATORY APPARATUS. 



Flourens determined the position of the respiratory center in the 

 medulla oblongata, behind the point of exit of the vagi, on either side 

 of the posterior extremity of the floor of the fourth ventricle, between 

 the nuclei of the vagus and accessory nerves. He designated this the 

 vital point OT n&ud vital, because its destruction is followed at once by 

 arrest of respiration and therefore by death. The center occupies ex- 

 actly the same situation in man, as Kehrer has demonstrated in a per- 

 forated new-born child. The center is bilateral, and it can be divided 

 by a median section, the respiratory movements continuing symmet- 

 rically upon both sides. If one vagus is divided the respiration be- 

 comes slowed upon the corresponding side. If, however, both vagi are 

 divided, the breathing is unequal in frequency and vigor on the two 

 sides of the body. Irritation of the central stump of one of the two 



