210 



Such is the origin of some of the most remarkable of the planetary 

 inequalities, and, in particular, of the great equations in the mean 

 motions of Jupiter and Saturn. It is necessary, therefore, that the 

 astronomer be furnished with the means of computing any term in the 

 expansion of the disturbing function below the sixth order j since it 

 has been found that there are inequalities depending upon terms of 

 the fifth order, which have a sensible effect on the motions of some of 

 the planets. The object of the author in the present paper is to give 

 the function such a form that the astronomer may have it in his power 

 to select any inequality he may wish to examine, and to compute the 

 coefficient of its argument by an arithmetical process of moderate 

 length. The investigation comprehends every argument not passing 

 the fifth order ; but as the formulae are regular, the method may be 

 extended indefinitely to any order. 



8. " On the Reflex Function of the Medulla Oblongata and Spi- 

 nalis, or the principle of Tone in the Muscular System." By Marshall 

 Hall, M.D., F.R.S. L. & E. 



The author, after commenting on the opinions of Le Gallois and 

 Cruveilhier relating to the functions of the spinal marrow, adverts to 

 a property or function of the medulla oblongata and spinalis, which 

 he considers as having escaped the notice of these and all other phy- 

 siologists ; namely, that by which an impression made upon the ex- 

 tremities of certain nerves is conveyed to these two portions of the 

 nervous system, and reflected along other nerves to parts different 

 from those which received the impression. He distinguishes muscu- 

 lar actions into three kinds : first, those directly consequent on vo- 

 lition 5 secondly, those which are involuntary, and dependent on simple 

 irritability ; and thirdly, those resulting from the reflex action above 

 described, and which include those of the sphincter muscles, the tonic 

 condition of the muscles in general, the acts of deglutition, of respi- 

 ration, and many motions, which, under other circumstances, are 

 under the guidance of the will. Volition ceases when the head or 

 brain is removed ; yet, as he shows by various experiments, move- 

 ments may be then excited in the muscles of the limbs and trunk, by 

 irritations applied to the extremities of the nerves which remain in 

 communication with the spinal marrow : but these actions cease as 

 soon as the spinal marrow is destroyed. Hence the author concludes 

 that they are the effect of the reflex action of the spinal marrow, 

 which exists independently of the brain j and, indeed, exists in each 

 part of the organ independently of every other part. He considers 

 that this reflex function is capable of exaltation by certain agents, 

 such as opium and strychnine, which in frogs produce a tetanic and 

 highly excitable state of muscular irritability. Hence he is led to view 

 the reflex function as the principle of tone in the muscular system. 

 He considers that certain poisons, such as the hydrocyanic acid, act 

 by destroying this particular function. The effects of dentition, of 

 alvine irritation, and of hydrophobia, of sneezing, coughing, vomiting, 

 tenesmus, &c. &c, are adduced as exemplifications of the operation 

 of the same principle when in a morbid state of exaltation. 



