456 Royal Society. 



by observing, that he does not touch upon the practical application 

 of the subject wherein the real value of the inquiry consists ; it is 

 his object to draw^ attention to an element w^hich, though in some in- 

 stances so minute in quantity as to be with difficulty detected in 

 our balances, has nevertheless been wisely assigned to discharge the 

 most important functions. 



" On the decussation of fibres at the junction of the Medulla Spi- 

 nalis with the Medulla Oblongata." By John Hilton, Esq. Com- 

 municated by P. M. Roget, M.D., Sec, R.S. 



The author first alludes to what usually happens in affections of 

 the brain, namely, that the loss of voluntary power and of sensation 

 manifest themselves in the opposite side of the body to that in which 

 the cerebral lesion exists, a fact which has been attempted to be ex- 

 plained by the crossing of the fibres at the junction of the medulla 

 oblongata with the anterior or motor columns of the medulla spina- 

 lis ; but such a structure, he observes, affords no explanation of the 

 loss of sensation. The author then, referring to the communication 

 of Sir Charles Bell to the Royal Society, in the year 1835*, descri- 

 bing a decussation connected with the posterior columns, or columns 

 of sensation, mentions that the accuracy of these dissections was 

 doubted by Mr. Mayo and other eminent anatomists. The author 

 proceeds to state that the symptoms of cerebral lesion do not always 

 take place on the opposite side of the body to that in which the le- 

 sion of the brain exists, but that they occur sometimes on the same 

 side ; that the loss of power and of sensation, although confined to 

 the same side, may exist in either the upper or the lower extremity ; 

 but that both are not necessarily implicated ; and that, in fact, cases 

 occur where there are marked deviations from what may be consi- 

 dered the more common occurrence. Having observed such cases, 

 and not being aware of any satisfactory explanation, the author ex- 

 amined with care the continuation upwards of the anterior and pos- 

 terior columns of the spinal marrow into the medulla oblongata, and 

 found that the decussation at the upper part of the spinal marrow 

 belonged in part to the columns for motion, and in part to the 

 columns for sensation ; and farther, that the decussation is only par- 

 tial with respect to either of these columns ; thus elucidating by the 

 observation of the actual structure what before appeared very un- 

 satisfactory in pathology, and anomalous in disease. 



The paper is illustrated by drawings made from the dissections of 

 the author. 



" Description of a self- registering Thermometer and Barometer in- 

 vented by the late James Coggan, Esq., and bequeathed by him to the 

 Royal Society." By Roderick Impey Murchison, Esq., F.R.S., 

 V.P.G.S., &c. 



The self-registering thermometer used by Mr. Coggan is of Six's 

 construction, and consists of a siphon tube, open at one extremity, 

 and operating by the expansion and contraction of a large body of 

 spirit pressing on a column of mercury in the lower bend of the tube. 



• See Lond. and Edinb. Phil. Mag., vol. vii. p. 138. 



