LATERAL SEMISECTION OF THE CORD. 867 



a clinical condition of acknowledged occurrence ensuing upon spinal 

 injuries. That in man such symptoms have been satisfactorily demon- 

 strated to be associated with uncomplicated and accurately limited 

 local destruction of one lateral half of the cord, cannot, however, be 

 affirmed. Experiments on animals have led some observers x to uphold 

 the view that Brown-Sequard first put forward and for some time held. 

 The general consensus of opinion and the greater weight of evidence 

 have been, however, both before and since Brown-Sequard's original 

 report, against it. That important ascending paths do cross in the cord 

 is beyond question. That they are ascending does not prove that they 

 are " sensory ; " the necessity of interpolating the remark emphasises the 

 drawback attending the time-honoured misuse of the term " sensory " 

 — as of "volitional" — in such connection. The increase of arterial 

 pressure, caused by faradising the central end of one sciatic nerve, 

 the cord having been at the hindmost thoracic level severed except 

 for one lateral column, is greater 2 if the nerve be contralateral to 

 the undivided column than if homonymous. This does not, I think, 

 prove that the path, even for impulses ascending to the bulbar vaso- 

 motor centre, is mainly contralateral ; it is as well explained by sup- 

 posing lumbar relay centres below the semisection more irritable 

 on the side of the semisection than on the comparatively normal side. 

 Similarly, in experiments 3 in which movements of the fore-limb were 

 used as index of ascendent conduction, the results in this connection 

 merely indicate that a spinal path up from the hind-limb has become 

 contralateral at the level of the lower thoracic region; the experi- 

 ments do not necessarily show that the crossed path is the main one. 

 There is the Van Deen i experiment in the frog : a lateral semi- 

 section of the cord close in front of the crural plexus (say right), then 

 a semisection of the opposite side close behind the brachial plexus. On 

 stimulating the skin of the left fore-limb, movement of each of all the 

 limbs is evoked ; on stimulating the skin of the right hind-limb, move- 

 ment of each of all the limbs is also evoked. Vulpian 6 affirmed that this 

 is true even when only one column of white matter connects the front 

 and posterior halves of the animal. He extended similar observations 

 to the dog. A semisection on the right side in the lumbar region 

 produced what he considered hyperesthesia in the right hind-limb, and 

 slight depression of sensory function in the left. A second semisection 

 on the left side at the fourth cervical level, practised a few hours after 

 the former semisection, caused the hyperesthesia of the right hind-limb 

 to disappear, but produced marked hyperesthesia of the left fore-limb. 



These results naturally lead to consideration of the well-known zonal 

 hypersesthesia occurring as the result of various kinds of spinal lesion. 

 It was noted, originally by Fodera, 6 that after partial transection of the 

 cord, stimuli applied to a zone of skin just posterior to the lesion evoked 

 signs of sensations more readily than normally. Fodera concluded also that 

 the muscles behind the section are more excitable by local reflex channels 

 than they normally are. The hyperaesthesia of Fodera is now a phenomenon 

 universally acknowledged. It includes hyperalgesia. It seems to ensue when 

 the spinal lesion involves the extreme dorsal part of the lateral column. 7 



1 Ferrier, "Functions of the Brain," 2nd edition ; W. A. Turner, loc. cit. 



2 Mieseher, Arb. a. d. physiol. Anst. zu Leipzig, 1870. 3 Woroschiloff, ibid., 1874. 



4 " Traits sur la physiologie d. 1. moelle £pin.," Leide, 1841. 



5 " Lecons sur le systeme nerveux," Paris, 1866. 6 Journ. dephysiol. cxper. , Paris, 1822. 

 7 JMartinotti, Arch. f. Physiol., Leipzig, Suppl., 1890. 



