1863.] 491 



drop of the cell-contents would be lodged between the outer and 

 inner membrane, and completely severed from the general cell-cavity. 

 The peculiar modification spoken of as the "hooded" appearance 

 might be due to imbibition of fluid between this microscopic drop 

 and the outer envelope. 



The chief difficulties in the way of this explanation arise out of 

 the differences of nature which appear to exist between the projection 

 and the general cell-contents of which it is supposed to be a detached 

 portion. The projection refracts light much more highly than the 

 cell-contents ; it also is deeply dyed by magenta, whereas the cell- 

 contents are only very feebly so. 



In conclusion, it may be added that important advantages may be 

 expected from the use of magenta in histological researches. Its 

 inert chemical character, its prodigious tinting power, and its solu- 

 bility in water eminently fit it for such a purpose. It will probably 

 prove of especial use in bringing into sight objects which otherwise 

 evade the visual organs from their absolute colourlessness and trans- 

 parency, and from the equality of their refraction with the medium 

 in which they exist. 



II. " On Quinidine, and some Double Tartrates of the Organic 

 Bases." By JOHN STENHOUSE, LL.D., F.R.S. Received 

 February 23, 1863. 



Quinidine, as is well known, was first observed by Henry and 

 Delondre, and likewise by Sertuerner, in what is called the " quini- 

 dine" of commerce, which consists chiefly of a mixture of quinidine, 

 quinine, and resinous matters obtained from the mother-liquors of 

 the sulphate-of-quinine manufacture. Van Heijningen, however, 

 was the first person who succeeded in separating quinidine, which he 

 called /3-quinine, from this mixture and in obtaining it in a pure and 

 crystalline state. He likewise ascertained that quinidine was iso- 

 meric with quinine. Its action on polarized light was studied by 

 Pasteur, who observed that its solution in absolute alcohol produces 

 deviation to the right, while a similar solution of quinine produces 

 rotation to the left (Buchardat). 



As comparatively few of the salts of quinidine have hitherto been 

 analysed, and those chiefly by Van Heijningeu, I was induced to 



