483 



to 30 sec. after its peak. Although the sequence of 

 events is too slow to suggest fiber interaction, efferent 

 sympathetic discharges had apparently set up pain 

 impulses at the periphery. 



We are not aware that any observer has reported 

 decreased appreciation of pinprick in man after 

 sympathectomy, but van Harreveld & .Smith (272) 

 thought that extensive thoracicoabdominal sympa- 

 thectomy produced additional loss of pain from the 

 skin in seven of eight lower thoracic and upper lum- 

 bar segments studied in the cat. They isolated a 

 dermatome by cutting three spinal nerves above and 

 three below the one they left intact. The borders of 

 this dermatome as determined by the motor respon.se 

 to pinching proved constant. After the sympathec- 

 tomy there was then an added loss of .sensitivity to 

 pinching in a small often triangular zone at the 

 cranioventral side of the dermatome. They sug- 

 gested that these sympathetic afferents might go to 

 the blood vessels of the skin. 



Parasympathetic Nerves 



Of the cranial autonomic nerves we shall mention 

 only the vagus. That this carries afferent fibers from 

 the trachea and bronchi is suggested by the finding of 

 Morton et al. (193) who relieved the pain and cough 

 of bronchogenic carcinoma by section of the homo- 

 lateral vagus below its recurrent laryngeal branch. 

 The presence of other afferent fibers perhaps from 

 the thoracic esophagus is intimated by the observa- 

 tions of Grimson et al. (112). Their patients under 

 spinal anesthesia experienced 'heartburn' and pain 

 referred to the neck when the vagus was stimulated 

 three inches above the diaphragm. Stimulation at or 

 below the diaphragm caused no pain, so the vagi 

 probably carry no such fibers from the abdominal 

 viscera. This was also the conclusion of Cannon in 

 his cats (38). 



The problem of pain conduction by afferent sacral 

 parasympathetic fibers is discussed by White & 

 Sweet (296, pp. 671 to 674). 



On balance it is our impression that afferent fibers 

 for pain are to i)e found in so many of the autonomic 

 nerves in man that no useful purpose is served by 

 regarding these as comprising a purely efferent ner- 

 vous system, the more so since a numl:)er of the con- 

 siderations which led to the development of this con- 

 cept by Ga.skell & Langley have been shown to be 

 invalid. 



SPIN.AL CORD 



Upon entry into the spinal cord the posterior root 

 filaments divide into a lateral bundle of fine fibers 

 and a medial bundle of large fibers. The small lateral 

 fibers bifurcate at once into two short branches one 

 of which passes rostrally, the other caudally, for a 

 few segments in the dorsolateral fasciculus or zone of 

 Lissauer (marginal zone of Waldeyer). Each branch 

 gives off collaterals which pass into the posterior 

 horn, according to Bok (29, p. 534). We have re- 

 ferred to the work of Ranson &. Billingsley (219) 

 in cats which places the pain fibers in the lateral 

 bundle. Hyndman (132) has contended that incision 

 into this zone in man produces an area of analgesia 

 without complete loss of touch sensation. R. W. Rand, 

 E. J. Penka and W. E. Stern, however, made in two 

 patients a total of 15 electrolytic lesions in the zone 

 of Lissauer and were unable to detect any sensory 

 changes attributable thereto. They made an even 

 more extensive series of rostrocaudal lesions in this 

 zone in a monkey, 10 in number, i mm deep from 

 the C6 through Ti cord segments. Examination 

 post-mortem showed the lesions extending but little 

 beyond the desired zone of destruction which had 

 produced analgesia only of the ulnar aspect of the 

 ipsilateral forearm and hypalgesia of the ulnar area 

 of the hand. Because of the above-mentioned rostro- 

 caudal fanning of the fibers, it is not surprising that 

 an extended continuous lesion is required to produce 

 any demonstrable sensory loss. 



The posterior root fibers terminate around : a) the 

 posteromarginal or perlcornual cells which lie 

 around the entire margin of the posterior horn, A) 

 the more centrally placed cells of the nucleus pro- 

 prius of the posterior horn and c) small cells lying 

 within the substantia gelatinosa which caps the nu- 

 cleus proprius, as shown in figure 7. Pearson (207) 

 from studies of his Golgi preparations of spinal 

 cords of human babies finds that these small cells 

 in the substantia gelatino.sa may intervene between 

 some of the primary afferent terminals and the 

 larger cells which lie in the nucleus proprius and in 

 the pericornual regions. The latter two groups of 

 cells give rise to the major crossed ascending af- 

 ferent pathways in the cord. Pearson hypothecates 

 that the primary afferent fibers which end directly 

 in relation to the.se latter cells would be likely to 

 give rise to 'fast pain,' whereas those cells contain- 

 ing a sinall intercalated neuron of the substantia 

 gelatinosa might be those evoking 'slow pain.' 



The pericornual cells are middle-sized ganglion 



