812 THE SPINAL CORD. 



behind the two nerve pairs of the brachial region, 1 and the wagging 

 of the monkey's tail after spinal transection in the anterior sacral 

 region. 2 These are comparable with the sting reflex of the bee for 

 which the hindmost abdominal ganglion pair is competent after 

 severance of the longitudinal nerve-cords just in front of it. 3 Mayo's 4 

 celebrated experiment on what Grainger 5 calls "a segment of the 

 cranial portion of the spinal cord," went far to draw attention 

 to the fractional powers of the cerebro -spinal organ. Having isolated 

 in the pigeon the " segment " composed of the optic tubercles and the 

 crura cerebri (the optic and third nerves being attached) by section from 

 the medulla oblongata and the brain, Mayo demonstrated that, on 

 pricking the stump of the optic nerve adhering to the optic tubercle, 

 the iris contracted. 



Description of spinal function is best introduced by a glance at the 

 organic reactions still possible in regions of the body whence the cord 

 has been in toto removed. The destruction of the cord removes the 

 corresponding region from all influence which the sense organs of its 

 own or other parts can bring to bear on it ; and also from the possibility 

 of influencing, by means of its own sense organs, other parts. The 

 rupture of these connections between it and the rest of the individual 

 falls with very unequal severity on the various organs composing the part ; 

 it falls with especial severity on the skeletal musculature. It also much 

 affects the circulation, at least for a time. If two frogs be placed 

 under curari, so as to eliminate movements, and the brain and spinal 

 cord of one be destroyed and of the other left intact, absorption 

 of sodium chloride (0'75 per cent.) solution takes place much more 

 copiously 6 from the dorsal lymph sac of the frog with intact spinal 

 cord than from that of the other. The destruction of the cord causes 

 dilatation of the splanchnic vascular area, so that the major part of the 

 blood remains almost stagnant in the portal blood vessels, and with the 

 enfeebled circulation the absorption from the lymph sac is but slight. 

 When in a mammal the lumbo-sacral region of the cord has been 

 exsected, 7 the recovery of innervation by the tissues of the correspond- 

 ing region appears, when tested by traumata, perfectly good. Ulcers 

 occasioned by pressure, etc., heal readily when treated. The surface 

 temperature is, after shock has passed by, maintained ; so is the rectal. 

 In the bitch the inguinal mammae still yield milk in the puerperium. 

 On application of cold to the skin, the blood vessels respond by 

 constriction and later flushing. The hair is shed and renewed in due 

 season. The rectum empties itself when distended ; so also the urinary 

 bladder, though not regularly. Pregnancy and labour occur, and in due 

 course are brought to successful issue. The constrictor cunnce is not 

 toneless, but fairly normally controls the vaginal orifice. The sphincter 

 of the anus in time recovers tone, remains tight, and reacts vigorously to 

 faradic stimulation. It also from time to time, especially immediately 

 after def secation, exhibits the rhythmic relaxations and constrictions first 



1 Spallanzani, "Opera," Moclena, 1768; Goltz, Centralbl.f. d. tried. Wissensch., Berlin, 

 1866. 



2 Sherrington, Phil. Trans., London, 1893, vol. clxxxiv. p. 641. 



3 Bethe, Arch. f. d. ges. PhysioL, Bonn, 1897, Bd. Ixviii. 



4 Herbert Mayo, " Anat. and Phys. Commentaries," London, 1823, vol. ii. pp. 4, 18, 

 136. 



5 "Structure and Functions of the Spinal Cord," London, 1837. 



6 Goltz, Arch. f. d. ges. PhysioL, Bonn, 1872, Bd. v. S. 53. 



7 Goltz and Ewald, ibid., 1896, Bd. Ixiii. 



