348 OF THE PRIMARY TISSUES OF THE HUMAN BODY. 



almost entirely recovered; and at the end of eleven months, no difference could 

 be discovered in the motor power of the two limbs. The animal was killed 

 twelve months after the operation ; and a careful examination having been insti- 

 tuted into the state of the part of the nerve where the division had been made, 

 no indication of the division could be discovered, either with the naked eye, or 

 with the microscope. The usual swelling at the point of reunion had been dis- 

 tinguishable up to about the sixth month; but it had then disappeared. The 

 results of M. Brown- Sequard's experiments upon the Spinal Cord are yet more 

 striking. The spinal cord of a pigeon having been divided between the fifth 

 and sixth dorsal vertebras, the completeness of the section was manifested by 

 the entire paralysis of the posterior part of the body, as regarded both sensation 

 and voluntary movement; at the end of three months, however, voluntary move- 

 ments began to show themselves in the midst of reflex actions, and sensibility 

 also reappeared ; these powers gradually augmented, and six months after the 

 operation the bird could stand for some minutes, though it fell if it attempted 

 to walk; in the course of the seventh month it began to walk, but unsteadily, 

 helping itself by its wings; by the end of the eighth month it could walk slowly 

 without support, though it fell over if it attempted to walk fast, unless it sup- 

 ported itself by its wings ; twelve months after the operation, it could run ; and 

 at the end of the fifteenth month its progression seemed in all respects normal, 

 save that a certain degree of stiffness remained in its gait. In several other 

 cases, in which a partial section of the spinal cord had been made, and in which 

 a complete return of functional power had taken place, a careful examination 

 was made of the divided part; this was distinguishable by a whitish cicatrix, 

 the substance of which was found to be in great part made up of fibres of areo- 

 lar tissue, the direction of which was transverse or oblique; but these were 

 crossed by great numbers of nerve-tubes running in a longitudinal direction, 

 which exhibited the characteristic double contour, and were uninterruptedly 

 continuous through the whole extent of the cicatrix; and amongst these were 

 scattered some ganglionic corpuscles. 1 



350. Functions of Nervous Tissue. The peculiar vital endowments of the 

 Nervous tissue can only be exhibited, when the two distinct forms of it are 

 united in such a manner as to constitute a "nervous system." This system in 

 its simplest condition, is composed of an expansion of nerve-fibres over the sur- 

 face of the body, or of some part of it; of an afferent trunk formed by the junc- 

 tion of these fibres, which proceeds towards a ganglion wherein it terminates; 

 of a ganglionic centre containing vesicular nervous matter, with which the nerve- 

 fibres come into connection; of an efferent trunk, issuing from the ganglion, and 

 proceeding towards the muscles; and of & plexus of fibres into which that trunk 



1 See the "Gazette Medicale," 1849, No. 45, and 1851, No. 30; also the "Comptes 

 Rendus de la Societe de Biologic," 1849, 1850. The successful issue of these experiments 

 is in great part attributable to the sedulous care bestowed by M. Brown-Sequard upon the 

 animals which are the subjects of them. It frequently happens that pathological changes 

 take place in the paralyzed parts, which may lead to serious or even fatal consequences ; 

 and such changes have been attributed to the direct influence of the withdrawal of nervous 

 power, upon the nutritive processes. It has been shown, however, by an experiment of 

 M. Brown-Sequard' s, that no such influence exists; and that the pathological changes in 

 question are due to the want of power on the part of the animals to withdraw their limbs 

 from sources of injury. For, having divided the sciatic nerve in a number of rabbits and 

 guinea-pigs, he placed some of the animals at liberty in a room with a paved floor, whilst 

 he confined others in a box, whose bottom was thickly covered with bran and hay. In a 

 fortnight, the former set exhibited an obvious disordered action in the paralyzed limbs, 

 the claws being entirely lost, the extremities of the feet swollen, and the exposed tissues 

 red, engorged, and covered with fleshy granulations ; and at the end of a month these alter- 

 ations were more decided, the bones being denuded, and necrosis having commenced in 

 them. On the other hand, among the animals confined in boxes with a soft floor, no such 

 injuries had accrued. 



