648 CONDUCTION IN THE SPINAL CORD. 



not of the painful sensations caused by the knife dividing the parts. As painful impressions 

 are conducted by the whole of the grey matter, and as the impressions are more powerful the 

 stronger the painful impression, we may thus explain the so-called irradiation of painful 

 impressions. During violent pain, the pain seems to extend to wide areas ; thus, in violent 

 toothache, proceeding from a particular tooth, the pain may be felt in the whole jaw, or it may 

 be over one side of the head. 



According to Bechterew, the paths for the conduction of painful impressions lie in the anterior 

 part of the lateral column (dog, rabbit). 



The experiments of Weiss on dogs, by dividing the lateral column at the limit of the dorsal 

 ami lumbar regions, showed that each lateral column contains sensory fibres for both sides. The 

 chief mass of the motor fibres remains on the same side. Section of both lateral columns 

 abolishes completely sensibility and motility on both sides. The anterior columns and the grey 

 matter are not sufficient to maintain these. 



6. The conduction of spasmodic, involuntary, inco-ordinated movements takes 

 place through the grey matter, and from the latter through the anterior roots. 



It occurs in epilepsy, poisoning with strychnin, ursemic poisoning, and tetanus ( 360, II. ). 

 The ana-mic and dyspneeic spasms are excited in and conducted from the medulla oblongata, and 

 communicated through the whole of the grey matter. 



7. The conduction of extensive reflex spasms takes place from the posterior 

 roots, perhaps to the cells of the posterior cornu and then to the cells of the anterior 

 cornu, above and below the plane of the entering impulse (fig. 458), and, lastly, 

 into the anterior roots, under the conditions already referred to in 360, II. 



8. The inhibition of pathic reflexes occurs through the anterior columns 

 downwards, and then into the grey matter to the connecting channels of the reflex 

 organ, into which it introduces resistance. 



9. The vaso-motor fibres run in the lateral columns (Dittmar), and, after they 

 have passed into the ganglia of the grey matter at the corresponding level, they 

 leave the spinal cord by the anterior roots. They reach the muscles of the blood- 

 vessels either through the paths of the spinal nerves, or they pass through the rami 

 communicantes into the sympathetic, and thence into the visceral plexuses 

 ( 356). 



Section of the spinal cord paralyses all the vaso-motor nerves below the point of section ; while 

 stimulation of the peripheral end of the spinal cord causes contraction of all these vessels. [Ott's 

 experiments on cats show that the vaso-motor fibres run in the lateral columns, and that they as 

 well as the sudorific nerves decussate in the cord.] 



10. Pressor fibres enter in the posterior roots, run upwards in the lateral columns, 

 and undergo an incomplete decussation (Ludwig and Miescher). 



They ultimately terminate in the dominating vaso-motor centre in the medulla oblongata, which 

 they excite reflexly. Similarly, depressor fibres must pass upwards in the spinal cord, but we 

 know nothing as to their course. 



11. From the respiratory centre in the medulla oblongata, respiratory nerves 

 run downwards in the lateral columns on the same side, and after forming connec- 

 tions with the ganglia of the grey matter pass through the anterior roots into the 

 motor nerves of the respiratory muscles (Schiff). 



Unilateral, or total destruction of the spinal cord, the higher up it is done, accordingly 

 paralyses more and more of the respiratory nerves, on the same or on both sides. Section of the 

 cord alwve the origin of the phrenic nerves causes death, owing to the paralysis of these nerves 

 of the diaphragm (113). 



In pathological cases, in degeneration of, or direct injury to, the spinal cord or its individual 

 parts, we must be careful to observe whether there may not be present simultaneously paralytic 

 and irritative phenomena, whereby the symptoms are obscured. 



[Complete transverse section of the cord results immediately in complete 

 paralysis of motion and sensation in all the parts supplied by nerves below the seat 

 of the injury, although the muscles below the injury retain their normal trophic 

 and electrical conditions. There is a narrow hyperaesthetic area at the upper limit 

 of the paralysed area, and when this occurs in the dorsal region, it gives rise to the 

 feeling of a belt tightly drawn round the waist, or the "girdle sensation." There 

 is also vaso-motor paralysis below the lesion, but the blood-vessels soon regain their 



