REPORT ON THE PHYSIOLOGY OF THE NERVOUS SYSTEM. 75 



tures that it also has the office of associating the partial con- 

 tractions of individual muscles into "mouvemens d'ensemble," 

 necessary to the regular motions of the limbs. 



Before recording what is known of the spinal cord itself, it 

 will be proper to advert to some recent experiments of Magen- 

 die on the serous fluid in which it is immersed. It would 

 appear that a quantity of liquid, varying from two to five 

 ounces in the human subject, is always interposed between 

 the arachnoid tunic and the pia mater, or proper membrane of 

 the cord. The intermembranous bag, occupied by this fluid, 

 communicates with the ventricular cavities at the calamus scrip- 

 torius by a round aperture, often large and patent in hydroce- 

 phalic subjects. Magendie has therefore named this serous 

 liquid ' cerebro-spinal'. In living animals, it issues in a stream 

 from a puncture of the arachnoid. Its removal occasions great 

 nervous agitation, and symptoms resembling those of canine 

 madness. The sudden increase of its quantity induces coma. 

 Its presence seems essential to the undisturbed and natural ex- 

 ercise of the nervous functions ; and this influence probably is 

 dependent upon its pressure, temperature and chemical con- 

 stitution, since any variation of these conditions is followed by 

 the phenomena of nervous disorder. 



The great medullary cord is divided by a double furrow into 

 two lateral halves ; and each of these is again subdivided by the 

 insertions of the ligamenta dentata into two columns, one pos- 

 terior and one anterior. It has been long known that section 

 of any part of the spinal marrow excludes from intercourse with 

 the brain all those parts of the body, which derive their nerves 

 from the cylinder of medulla below the point of injury. The 

 muscles, so supplied, are no longer obedient to the control of 

 the will, and the tegumentary membranes similarly situated en- 

 tirely lose their sensibility. This interruption of the relations 

 which subsist between the central seat of volition and sensation, 

 and the rest of the body, whether due to direct injury of the 

 great nervous masses or comnumicating nerves, or pi'oduced by 

 the pressure of extravasated fluids, by morbid growths, or by 

 various poisonous matters, constitutes the condition known by 

 the name ' paralysis'. In cases of this kind it is frequently ob- 

 served that the powers of sensation and locomotion are simulta- 

 neously impaired or destroyed. But examples are not want- 

 ing, even in the earliest clinical records, of the total loss of one 

 of those faculties with perfect integrity of the other. Such facts 

 naturally suggested the belief that the power of propagating 

 sensations, and that of conveying motive impressions, resided 

 in distinct portions of the nervous system. This opinion, how- 



