548 THE MICROSCOPE. 



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 contents, being 

 thicker than the outer membrane, and composed of a 

 protein compound, are the colouring-matter constituting 

 the redness of the corpuscles. The red corpuscles of birds, 

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

 those of the human subject and other Mammifera, 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 colour- 

 ing-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 spon- 

 taneously certain changes, one of the most common is a 

 wrinkling up of the walls, with a surface somewhat like 

 that of a mulberry; this may also be produced by mecha- 

 nical 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 of water, are seen as nucleated 

 cells, whose diameter is about the l-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 ia 

 seen as if there were several nuclei aggregated together. 

 This latter appearance was considered to be the natural 

 state of the nucleus, the particles of which were either 

 tending to unite with one another, or there was a sepa- 

 ration of the nucleus into several smaller portions, 



