3 



but chiefly obliquely, by tubular nerve-fibres and blood-vessels, 

 which proceed from the gray substance on each side and decussate 

 in front of the spinal canal : nor are the posterior white columns 

 connected by any commissural fibres, the posterior fissure reaching 

 down to the gray substance. 



Origin of the Spinal Nerves. — The posterior roots are attached 

 exclusively to the posterior columns. Their fibrils generally are 

 finer than those of the anterior roots. The anterior roots are at- 

 tached to the anterior parts of the antero-lateral columns, which they 

 traverse horizontally in straight bundles, till they reach the anterior 

 horns, in which they break up and form a complicated network. 

 The author has not yet been able to determine whether any of the 

 fibres of the spinal nerves ascend with the longitudinal white columns. 



December 12, 1850, 



SIR FREDERICK POLLOCK, Lord Chief Baron, V.P., in 

 the Chair. 



The following letter from M. Arago to Lieut. -Col. Sabine was 

 read, and ordered to be entered on the Minutes. 



Paris, Dec. 8, 1850. 



" MoN CHER Monsieur, — Mon age, ma mauvaise sante, I'etat 

 deplorable de mes yeux, et la part que j'ai du prendre aux evene- 

 ments dont mon pays a ete le theatre depuis le 24 Fevrier 1848, 

 m'avaient fait supposer que j'etais entre dans cette periode de la vie 

 oil rien ne peut produire une vive impression. Votre lettre ma de- 

 trompe. La nouvelle que la Societe Royale avait bien voulu m'ac- 

 corder pour 1849 et 1850 la medaille de Rumford m'a comble de joie. 

 Veuillez etre aupres de vos honorables confreres I'interprete de mon 

 inalterable reconnaissance ; dites leur surtout, que leur indulgence 

 me fera redoubler d'efforts pour que les travaux qui me restent a 

 publier ne soient pas indignes de la faveur dont j'ai ete I'objet. 



" Agreez, mon cher Sabine, Texpression de tous mes sentiments. 



"F. Arago." 



A paper was then read, entitled, " On the Action of Nitric Acid 

 on various Vegetables, with a more particular examination of Spar- 

 tium scoparium. Linn., or Common Broom." By John Stenhouse, 

 Esq., F.R.S. Received November 18, 1850. 



This paper is a continuation of a series of investigations intended 

 to elucidate the nature of vegetables by means of chemical reagents. 

 A preceding paper contained an account of the effects produced 

 by the action of sulphuric and hydrochloric acids on the matiere 

 incrustante of several plants belonging to different great classes of 

 vegetables. The effects of nitric acid upon a variety of vegetable 

 groups are now described ; the researches having been undertaken 

 in the hope that by means of this powerful reagent some light might 

 perhaps be thrown on peculiarities in their respective constitutions. 



1* 



