71 



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 ; 



