FUNCTIONS OF THE SPINAL CORD. 701 



which they remain connected, be so unduly irritable, that the muscles are called 

 into contraction upon the slightest excitation, and are thus continually exhi- 

 biting twitchings, startings, or more powerful convulsive movements. It is 

 upon the state of nutrition of the muscles that their contractility depends 

 ( 313) ; and hence the Spinal Cord has an indirect influence upon this peculiar 

 property, which is more likely to be retained, when the muscle is still subject 

 to the influence of the Spinal Cord, though cut off from that of the Brain, than 

 when it is completely paralyzed by the entire separation of its connection with 

 the nervous centres. 



728. The functional activity of the Spinal Cord is capable of being morbidly 

 diminished or augmented. It may even be for a time almost completely sus- 

 pended, as in Syncope ; which state may be induced by sudden and violent 

 impressions, either of a mental or physical nature, that operate upon the whole 

 nervous system at once commencing, however, in the Brain. It is to be 

 remarked that, in recovering from these, it is the Spinal system of which the 

 activity is first renewed; the respiratory movements recommencing, and the 

 power of swallowing being restored, before any voluntary actions can be per- 

 formed. A corresponding state may be induced in particular portions of the 

 system by Concussion ; as is seen in severe injuries of the Spinal Cord, which 

 are almost invariably followed for a time by the suspension of its functions. 

 Again, the power of the whole Spinal Cord may be diminished by various 

 causes, such as enfeebled circulation, pressure, &c. ; and then we have torpidity 

 and imperfect nutrition of the whole muscular system. 1 If oppression exist in 

 the Brain, the functions of the Medulla Oblongata will be especially affected ; 

 and if it be prolonged and sufficiently severe, Asphyxia will result from the 

 interruption of the respiratory movements which it occasions. On the other 

 hand, the excitability of the whole Cord, or of particular parts of it, may be 

 morbidly increased. 3 This is especially seen in ordinary Tetanus, and in the 



1 A case has been for some time under the Author's observation, in which the males of a 

 family have been successively aifectcd with a general muscular debility, commencing in the 

 lower extremities, which is pretty obviously traceable to deficient functional activity of the 

 Spinal Cord. The affection has manifested itself during the earlier years of childhood ; and 

 in the two elder sons has advanced until it has produced an almost complete general paralysis, 

 with fatty degeneration of the muscles. In a younger son, in whom the same affection had 

 distinctly begun to manifest itself, it has been kept in check by very careful attention to 

 every means that can favor healthy nutrition and development of nervous power ; among 

 which, constant exercise, and the frequent transmission of feeble electrical currents down 

 the spine and from the spine to the limbs, have seemed the most effectual. 



2 It has been pointed out by Messrs. Todd and Bowman ("Physiological Anatomy," 

 p. 281, Am. Ed.} that the Spinal Cord of the male frog, at the season of copulation, naturally 

 possesses a state of most extraordinary excitability. The thumb of each anterior extremity, 

 at this season, becomes considerably enlarged ; as is well known to Naturalists. "This 

 enlargement is caused principally by a considerable development of the papillary structure 

 of the skin which covers it ; so that large papillas are formed all over it. A male frog, at 

 this season, has an irresistible propensity to cling to any object, by seizing it between his 

 anterior extremities. It is in this way that he seizes upon, and clings to the female ; fixing 

 his thumbs to each side of her abdomen, and remaining there for weeks, until the ova have 

 been completely expelled. An effort of the Will alone could not keep up the grasp unin- 

 terruptedly for so long a time ; yet so firm is the hold, that it can with difficulty be relaxed. 

 "Whatever is brought in the way of the thumbs, will be caught by the forcible contraction 

 of the anterior limbs ; and hence we often find frogs clinging blindly to a piece of wood, or 

 a dead fish, or some other substance which they may chance to meet with. If the finger 

 be placed between the anterior extremities, they will grasp it firmly ; nor will they relax 

 their grasp until they are separated by force. If the animal be decapitated, whilst the 

 finger is within the grasp of its anterior extremities, they still continue to hold on firmly. 

 The posterior half of the body may be cut away, and yet the anterior extremities will still 

 cling to the finger ; but immediately that the segment of the cord, from which the anterior 

 extremities derive their nerves, has been removed, all their motion ceases. This curious 

 instinct only exists during the period of sexual excitement ; for at other periods the excita- 

 bility of the anterior extremities is considerably less than that of the posterior." 



