Page:Proceedings of the Royal Society of London Vol 4.djvu/93

Rh influence and importance of nitrogen in vegetable physiology, by noticing, in the first place, the experiments of Dr. Daubeny, M. De Saussure, Sir Humphry Dav}', and those which he himself has m.ade ; all of which tend to prove that nitrogen is evolved during the healthy performance of the functions of plants ; that the proportion which it bears to the oxygen given off is influenced by the sun's rays ; but that owing to the necessar}^ exclusion of the external atmosphere during the progress of the experiments, it is impossible, with any degree of accuracy, to calculate the volume of these evolved gases during any period of the growth of plants in their natural state.

If to this indefinite quantity of nitrogen given off by plants there be added that definite volume incorporated into their substance and shown in the author's former tables, the question arises, whence do plants derive their nitrogen, and does any part of it proceed from the atmosphere } A problem which the author proposes to solve by a series of tabulated experiments upon seeds, and seedling plants, indicating a large excess of nitrogen in the latter, and under such circumstances of growth that he is compelled to fix upon the at- mosphere as its source.

By the same mode of experimenting, the author attempts to show that the differences which we find in the germination of seeds and the growth of plants in the shade and sunshine, are apparently due in a great measure to the influence of nitrogen. And he concludes 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 which, 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 aff"ections 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 obseri^es, affords no explanation of the loss of sensation. Tlie 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 ;