642 FUNCTIONS OF THE CEREBRO-SPINAL NERVOUS SYSTEM. 



from above, and nearly the whole of the Spinal Cord may be removed from 

 below, without the destruction of life, yet a complete stop is put to the cur- 

 rent of vital action when the Medulla Oblongata is destroyed. But the 

 dependence of the vital activity of the body generally upon the functional 

 integrity of this part of the nervous system, is simply consequent upon the 

 fact that the Medulla Oblongata contains the chief ganglionic centre of the 

 Respiratory movements; 1 upon the continuance of which, as already shown 

 (chap, ix, sect. 3), the continuance of the Circulation is dependent, and with 

 this, the maintenance of the Organic functions generally. Where, however, 

 as in the Frog, the respiratory activity of the skin is equal to or greater than 

 that of the lungs, the removal of the Medulla Oblongata is not attended by 

 fatal results, and M. Browu-Sequard 2 has kept frogs thus mutilated alive for 

 eight months. Besides the respiratory the following Gauglionic centres are sit- 

 uated within the Medulla Oblongata. 1. The centre of mastication. 2. The 

 centre of deglutition. 3. The centre of mimetic expression. 4. The centre 

 of speech so far as this is connected with the movements of the lips, tongue, 

 and larynx. 5. The centres governing the movements of the heart (accel- 

 erating and inhibitory ganglia). 6. The greater part of the vaso-motor centre. 

 7. The cilio-spinal centre. According to Budge this centre, which governs 

 the movements of the iris, is partially, and according to Salkowsky wholly, 

 imbedded in the Medulla Oblongata. It is remarked by Mr. Lockhart 

 Clarke 3 that it is probable the Olivary bodies are not only the centres 

 through which different movements are co-ordinated for expressing the pas- 

 sions and emotions, but that they are the motor centres through which dif- 

 ferent movements are effected by' sudden, violent, or peculiar impressions on 

 the special senses ; for they are intimately connected with all the sensory 

 ganglia of the Medulla, with the gray tubercle (trigeminus), the vagal 

 nucleus, the post pyramidal and restiform nuclei (auditory ganglia), and 

 the corpora quadrigemina (optic ganglia) through the fillet, and not im- 

 probably with the parts about the root of the olfactory bulb, since he has 

 been able to trace the olivary columns nearly to the anterior perforated 

 space. As regards the functions of the several strands composing the Me- 

 dulla Oblongata, little is known, excepting that the anterior pyramids are 

 the conductors for voluntary motor impulses. The Corpora Restifonnia, 

 which constitute the inferior peduncles of the Cerebellum, do not appear^ 

 according to M. Brown-Sequard, 4 to give passage to any of the conductors of 

 sensory impressions proceeding from the trunk, limbs, or head. It is remark- 

 able, however, that after they have been transversely divided, hypenesthesia 

 is produced in every part of the trunk and limbs. 



507. Hence the Spinal Cord, with its Encephalic prolongation, may be 

 said to supply by its "reflex power" the conditions requixifi' for the mainte- 

 nance of the various tiiuxrnlitr inorniinttx ir/iich arc ewitfial to tin 1 confiiiiiinK-e 

 of the Organic processes; and, as Dr. Hall has pointed out, it especially 

 governs the various orifices of ingress and egress. Thus, the act of Degluti- 

 tion is entirely dependent upon the Spinal Axis and the nerves proceeding 

 Iron) it; the Will being in no other way concerned in it, than by originat- 

 ing the necessary stimulus; and even sensation not being a necessary link 

 in the chain of excito-motor action ( 88-00). The action of the cardiac- 

 sphincter, again, and probably that of the p 

 pendent upon its nervous connection with the 



sphincter, again, and probably that of the pyloric sphiucter also, is de- 



'ie Spinal Axis; and is entirely 



1 Rrown-Se.pianl considers that the whole liase of the Encephalon in Man is im- 

 plicated in Respiration (Central Nervous Sy>tem, p. 191). 



2 Central Nervous System, 1800, p. 191. 



3 Philo.Miphieal Transactions, isc.8, p. 319. 4 Il>ul., p- 27. 



