616 Dynamic Theory. 



In the - medulla oblongata, then, are the centers for the co-ordination 

 of the movements concerned in respiration, and in the modifications and 

 interruptions of it, in coughing, vomiting, sneezing, singing, talking, 

 &c. The hypoglossal, glosso-pharyngeal, facial, and fifth nerves, which 

 are concerned in the co-ordination necessary for swallowing, either as af- 

 ferent or efferent, all originate in the gray nuclei in the medulla. The 

 muscular movements necessary for articulate speech, are co-ordinated in 

 the medulla oblongata, the nerves concerned being the hypoglossal, the 

 vagus, accessory, facial, and glosso-pharyngeal. Cries, exclamations, 

 and other forms of vocal expression, are co-ordinated in the medulla. 



The breathing apparatus has its nucleus of co-ordination in the nuclei 

 of the vagus nerves, near the beak of the calamus scriptorius. The 

 stimulations which are co-ordinated are those from the lungs themselves, 

 through the vagus, and also those from the general nervous system, es- 

 pecially of the head and face. The state of the blood has an effect on 

 respiration. The end, or object, of respiration, is the oxidation of the 

 blood, so that if the blood be hyper-oygenated, the movements of res- 

 piration automatically stop, and if any cause prevents oxidation of the 

 blood, the automatic efforts to breathe will be greatly stimulated 



All these automatic and reflex regulations of the blood pressure, are 

 co-ordinated through the medulla oblongata, and they may go on all 

 right even when all the brain centers above the medulla are abolished. 

 Respiration, heart-beating, and blood circulation, swallowing food put 

 into the mouth, digesting it, performing variSus reflex and even highly 

 complicated movements of limbs and jaws and throat, involving the ut- 

 terance of cries, &c. , are accomplished through the action of the nerve 

 centers of the medulla oblongata when the cerebral hemispheres and the 

 rest of the ganglia are gone. The vaso-motor region, or the centers in- 

 fluencing the tone of the blood vessels, blood pressure, &c. , are in the 

 anterior portion of the lateral tracts of the medulla. 



The interference of the centers in the medulla with the beating of the 

 heart, was mentioned in chapter 53. The immediate effect of this in- 

 terference from some of the centers, is acceleration of heart movement, 

 and the excitement of these centers, which thus overflows to the heart, 

 may be aroused by the active exercise of the muscles. When muscular 

 exertion takes place, nervous energy is evolved, which passes up the af- 

 ferent muscle nerves to the medulla, and thence down the acceleration 

 nerves b} r way of the first dorsal sympathetic ganglia to the heart, which 

 thus receives a double stimulation ; viz. , first, that habitually made in 

 its own tissues by the consumption of the blood furnished by its coro- 

 nary arteries ; second, that which is thus casually furnished by the 

 blood used up in a distant muscle. The effect of the acceleration is to 

 furnish more blood to the part at work. 



