384 Royal Society. 



6. " Physiological inferences derived from Human and Compara- 

 tive Anatomy respecting the Origins of the Nerves, the Cerebellum, 

 and the Striated Bodies." By Joseph Swan, Esq. Communicated 

 by Richard Owen, Esq., F.R.S. 



The author remarks that those parts of the nervous system which 

 are concerned in motion and in sensation exhibit a great similarity 

 in all vertebrate animals. To the first of these functions belong the 

 anterior and middle portions of the spinal cord and medulla oblon- 

 gata, including the anterior pyramids, the crura cerebri, and some 

 fibres leading to the corpora striata and the convolutions, and also 

 the cerebellum. To the function of sensation belong the posterior 

 surface of the spinal cord, the posterior and lateral portions of the 

 medulla oblongata, including the posterior pyramids, the ventricular 

 cords, and the fourth and third ventricles. 



From a general comparison of the relative magnitude and struc- 

 ture of these several parts in the different classes of vertebrated 

 animals, the author infers that only a very small portion of the brain 

 is necessary for the origins of the nerves, their respective faculties 

 being generally derived near the place at which they leave the brain. 

 These origins are traced in various cases, where, from peculiarities 

 of arrangement or of destination, they present certain remarkable 

 differences of situation. 



The author is led to consider the cerebellum as an appendage 

 to the brain, rather than to the medulla oblongata and spinal 

 nerves, for it does not correspond with either the number or the 

 size of the sensitive or motor nerves ; and that it is not required 

 for the intellect, for the special senses, for common sensation, or for 

 volition, appears from its size bearing no proportion to the strength of 

 any of these faculties. Neither is it concerned in digestion or assi- 

 milation, nor does its size present any relation with the heart, the 

 lungs, the muscles, the limbs, the vertebrae, the ribs, or any other 

 organ, not even those of reproduction. As, however, its nervous 

 connexions are principally with those parts which are exclusively 

 subservient to the will, it is probable that it is concerned in the 

 completion, and not in the commencement of the voluntary act. It 

 is probable, also, that the principal crossing of impulses from one 

 side to the other takes place in the medulla oblongata and the motor 

 tracts of the brain. Some of the arrangements of its lobules may 

 have reference to the paces and attitudes of different animals. The 

 will, acting through the cerebral convolutions, sets in action certain 

 muscles placed in proper directions ; but the influence of the cere- 

 bellum is required for giving them steadiness amidst the alterna- 

 tions from one set to another, and- especially when a slight change 

 disturbs the centre of gravity, and until the balance is effectually 

 restored by a subsequent act of the will operating on antagonist or 

 other muscles. The cerebellum also constitutes an additional focus 

 of nervous influence, and may, therefore, cooperate with the brain 

 in increasing the vital powers, and imparting greater energy to the 

 various functions of the body. 



The author regards the corpus striatum as being a centre for con- 



