678 THE MICROSCOPE. 



the lower animals a similar tinted particle appeared when 

 the corpuscles were treated with magenta. The conclusion 

 to be drawn from this and other observations noted by 

 Dr. Roberts, is that a duplication at one. or at most at 

 two points only, is indicated by direct proof ; but certain 

 appearances occasionally observed ivour the notion of a 

 complete duplication. 



The wall of the cell is a transparent structureless mem- 

 brane, and is of greater thickness than we find the analogous 

 membrane of cells to be generally. The red corpuscles of 

 birds, reptiles, &c. possess a distinct nucleus ; but, on 

 examining those of the human subject and other Mam- 

 malia, no distinct nucleus can be made out. By applying 

 dilute acetic acid, the red corpuscle becomes bleached, and 

 its walls distended, but no nucleus appears. If a red cor- 

 puscle from the Frog be treated in the same manner, we 

 see a nucleus, and the red colouring matter is drawn out 

 by exosmosis. Water causes the corpuscle to swell up, 

 and the colouring- matter disappears, but its real nature is 

 masked ; upon employing a drop of solution of iodine, the 

 wall is coloured or tinged, and made distinct. The cells 

 themselves have a tendency to undergo spontaneously 

 certain changes, one of the most common is a wrinkling up 

 of the walls, with a surface somewhat like that of a mul- 

 berry ; this may also be produced by mechanical pressure, 

 the addition of oil, &c. 



There is another set of corpuscles, slightly larger than 

 the red set ; these are termed colourless corpuscles, which, 

 when distended by the action o, f water, are seen as nucleated 

 cells, whose diameter is about the 1-2, 500th of an inch, 

 and a double contour of the walls is observed ; sometimes 

 there is a slight tinge of colour to be seen in the nucleus. 

 There is a third kind of corpuscles in the blood, more 

 numerous than those above referred to, but of about the 

 same diameter ; when distended, they are seen to be cells 

 filled with granular matter ; sometimes a clear spot is 

 noticed on one side ; very dilute acetic acid being applied, 

 the granules are dissolved out, and a clear central nucleus 

 remains, if the acid be used stronger, an appearance is 

 seen as if there were several nuclei aggregated together. 

 This latter appearance was considered to be the natural 



