856 THE SPINAL CORD. 



subsidiary spinal lies also in that region of the transverse area of the cord, 

 and, though mainly uncrossed, is partly crossed. Lateral semisection of 

 the cord in the cervical region has been found to depress the arterial pressure 

 very little ; the temperature of the skin of the head, forearm, hand, leg, and 

 foot becomes for the time higher on the side of the semisection l than on the 

 opposite ; contrarily, that of the trunk, shoulder, upper arm, and thigh is 

 lower on the side of the lesion ; this latter is probably due to the depression 

 of tonus in the skeletal musculature. But the subject is still not clear. A 

 wound of the dorsal column, for instance, produces a rise of temperature in the 

 foot of the homonymous side, although there then can be no question of 

 breaking of vaso-constrictor paths. After transverse lesions of the human 

 spinal cord, the surface veins of the lower limbs are swollen, and the tempera- 

 ture of the feet is often higher than that of the hands. 2 Priapism is also 

 a common symptom, and probably indicates vasomotor paralysis rather than 

 heightened reflex excitability. 



The heart and blood vessels can be regarded not only in virtue of their 

 musculature as organs of expression for reflexes, but also to some extent as 

 constituting a region whence reflexes can be initiated. Heger 3 injected into 

 the crural artery, the crural vein being tied, a minute quantity of nitrate 

 of silver solution, a salt to which it is believed the capillary wall is 

 impermeable. The quantity injected was believed sufficient to extend into 

 the capillaries. The injection caused an immediate alteration of the general 

 blood pressure, even when the sciatic nerve was the only structure undivided 

 at the root of the limb. The heart itself is a reflexigenous region of potency. 

 Harvey's observations on Viscount Montgomery showed, as have all 

 similar opportunities, that mechanical contact, even with some pressure applied 

 from without, is an inadequate stimulus to the sense organs of the normal 

 heart as regards the production of sensation. The afferent channels of the 

 heart, however, are not, so far as yet known, any of them spinal ; all, as far 

 as investigated, run in the vagus nerve. From the endocardium and the 

 pericardium, both visceral and parietal, under mechanical and chemical excita- 

 tion, muscular, respiratory, and vascular reflexes have been provoked. 4 From 

 the cardiac branches of the vagus have been excited, under certain circum- 

 stances, not only their well-known effects on blood pressure (through bulbar 

 vasomotor centre) and on rhythm of cardiac beat, but general reflexes affecting 

 the skeletal musculature. 5 The efferent channels connected with the cardiac 

 afferent are therefore far from confined to vascular nerves. .But further state- 

 ment of vascular and heart reflexes belongs to the chapters on the circulation. 6 

 Increased frequency of heart beat can, it seems, be evoked as a spinal reflex. 



Significance of spinal reflexes. The reactions of the skeletal 

 musculature obtainable from the " spinal " animal in response to stimuli 

 applied to its sense organs, exhibit often such obvious propriety as 

 replies to those stimuli that they are termed " purposive." Some have 

 regarded them as evidence of " conscious choice." 7 



1 v. Bezold, "Ueber d. gekreuzt. Wirk. d. Riickenmarks, " Berlin, 1859; Schiff, 

 "Lehrbuch d. Nerven- u. Muskel- Physiol.," Lahr, 1859. 



2 Th. Kocher., Mitt. a. d. Grenzgeb. d. Med. u. Chir., Jena, 1896, Bd. i. S. 555. 



3 Beitr. z. Physiol. C. Ludwig gew., Leipzig, 1887, S. 193. 



4 Budge, Arch. f. physiol. HeilJc., Stuttgart, 1846, Bd. v. S. 588 ; Goltz, Virchoiv's 

 Archiv, 1863, Bd. xxvi. S. 5; Gurboki, Arch. f. d. ges. Physiol., Bonn, 1872, Bd. v. 

 S. 289 ; Fran9ois-Franck, Trav. du lab. de Marey, 1880, tome iv. p. 382. 



5 Budge, Arch. f. physiol. ffeilk., Stuttgart, 1846, Bd. v. S. 588; Goltz, Virchow's 

 Archiv, 1863, Bd. xxvi. S. 5 ; Gurboki, Arch. f. d. ges. Physiol., Bonn, 1872, Bd. v. 

 S. 289. 



6 The spinal "sweat" centres and their connections are also treated elsewhere in this 

 work (see Waymouth Reid, vol. i. p. 676). 



7 E. Pfliiger, " Untersuch. ueber d. sensor, funct. d. Ruckenm.," Berlin, 1854. 



