NERVES OF MOTION. 397 



there are separate nerves for the two functions, although they may be 

 enveloped in the same neurilemma or nervous sheath; and may consti- 

 tute one nervous cord. We have more than once asserted, that the 

 posterior part of the spinal marrow, with the nerves proceeding from, 

 it, has been considered to be chiefly concerned in the function of sen- 

 sibility; and the anterior column, and the nerves connected with it, to 

 be inservient to muscular motion; whilst a third intervening column, 

 in the opinion of Sir Charles Bell, is the source of all the respiratory 

 nerves, and of the various movements connected with respiration and 

 expression. It is proper, here again, to observe, that although these 

 two distinguished physiologists agree in their assignment of function to 

 the anterior and posterior columns of the spinal marrow, Bellingeri 1 

 has deduced very different inferences from like experiments. He 

 asserts, that having divided, on living animals, either the anterior roots 

 of the spinal nerves, and the anterior column of the medulla spinalis 

 or the posterior roots of these nerves, and the posterior column of the 

 marrow, he did not occasion, in the former case, paralysis of motion, 

 and in the latter, loss of sensation ; but only, in the one, the loss of all 

 movements of flexion; and in the other, of those of extension. In his 

 view, the brain and its prolongations, crura cerebri, corpora pyra- 

 midalia, anterior column of the spinal marrow, and the nerves con- 

 nected with it, preside over the movements of flexion; and, on the 

 contrary, the cerebellum and its extensions, as the posterior column of 

 the medulla spinalis, and the nerves connected with it, preside over 

 those of extension: he infers, in other words, that there is an antago- 

 nism between these sets of nerves. The primd facie evidence is against 

 the accuracy of Bellingeri's experiments. The weight of authority 

 in opposition to him is, in the first place, preponderant; and in the 

 second place, it seems highly improbable, that distinct nerves should 

 be employed for the same kind of muscular action. Moreover, in 

 experiments on the frog, Professor Miiller established the correctness 

 of the views of Bell. It seems, that the different physiologists, who 

 engaged in the inquiry before he did, employed warm-blooded animals 

 in their experiments, and he imagines, that the pain, resulting from 

 the necessarily extensive wounds, may have had such an effect on the 

 nervous system as to modify, and perhaps even counteract, the results. 

 Muller employed the frog, whose sensibility is less acute, and tenacity 

 of life greater. If the spinal marrow of this animal be exposed, and 

 the posterior roots of the nerves of the lower extremities be cut, not 

 the least motion is perceptible when the divided roots are touched by 

 mechanical means, or galvanism. But if the anterior roots be touched, 

 the most active movements are instantly observed. These experiments, 

 Miiller 2 remarks, are so readily made, and the evidence they afford is 

 so palpable, that they leave no doubt as to the correctness of the views 

 of Sir Charles Bell. 



1 Exper. Physiol. in Mecl. Spinal. August, Taurin., 1825; Ragionamenti, Sperienze, &c., 

 comprovanti I'Antagonismo Nervoso, &o. Torino, 1833; and an Analysis of tbe same, in 

 Edinb. Med. and Surg. Journ., Jan., 1835, p. 160. 



3 Elements of Physiology, by Baly, p. 644,Lond., 1838. 



