266 SPECIAL PHYSIOLOGY. 



noid portion of the glottis is more easily closed. The lungs exhibit 

 congestions, extravasations of blood, and infiltration with serous fluid ; 

 the bronchial tubes become filled with mucus, so as to prevent the pas- 

 sage of air arid the interchange of gases, the result being a gradual 

 asphyxia. Irritation of the central portion of the divided vagus nerve, 

 in the neck, produces acceleration of the movements of the inspira- 

 tory muscles, for example, of the diaphragm and external intercostals. 

 The lower part of the oesophagus is paralyzed by division of both vagi 

 in the neck ; deglutition is impossible ; the food is arrested in its de- 

 scent, and is vomited, and if again swallowed is once more ejected ; 

 the movements of the stomach are also arrested ; the food now sta- 

 tionary is only digested on its surface ; the secretion of the gastric 

 juice is merely diminished, not arrested ; absorption continues unin- 

 terrupted. It would, appear, furthermore, that the vagus has a cer- 

 tain influence on the movements of the small and large intestines. 

 Division of both nerves accelerates the action of the heart ; irritation 

 of the distal portion of the divided nerve diminishes, or even arrests, 

 it. Section of these nerves arrests the formation of sugar in the liver ; 

 this process, however, is resumed on irritation of either of the cut ends 

 of the nerve ; the effect, in the case of irritation of the central end, is 

 propagated through the nervous centres, and thence to the sympathetic 

 nerve. 



In a beheaded criminal, fifteen minutes after execution, it was found 

 that the auricular contractions of the heart, which were still 60 to 70 

 per minute, were suddenly stopped by electrical shocks applied to the 

 left pneumogastric nerve, the auricle remaining distended ; electrical 

 stimulation of the sympathetic, re-excited the movementiS. Hence it 

 .has been supposed that the vagus exercises an inhibitory action, 

 .rhythmically with respect to the sympathetic ; but weak electrical 

 currents applied to the former nerve itself, rather quicken the heart's 

 -action. 



The spinal accessory nerve is not merely a motor root belonging to 

 ithe pneumogastric, although it communicates motor fibres to that 

 -nerve ; for it contains itself some sensory fibres. The exposure of 

 this nerve by opening the cranium, is so speedily fatal to an animal, 

 that experiments, for the purpose of determining its function, have 

 .been made by tearing out the nerve. This does not impair any of the 

 movements which are regulated through the pneumogastric nerve, such 

 as the respiratory movements ; but swallowing is interfered with, and 

 when both nerves are torn out. the voice ceases, the animal emitting 

 only a bubbling noise. Extirpation of one accessory nerve causes 

 hoarseness. Thus it appears that the spinal accessory nerves govern 

 the momentary and voluntary opening or closure of the glottis, and 

 the tension of the vocal cords necessary for the production of voice, or 

 for the exercise of general muscular effort ; whilst the respiratory 

 movements of the glottis are under the control of the pneumogastrics. 

 Deglutition is merely rendered difficult, because the pharyngeal and 

 oesophageal branches of the glosso-pharyngeal and vagus are still in 

 operation. Irritation of the roots of this nerve produces contractions 

 in the oesophagus, pharynx, and larynx, as well as in the trapezius 



