Influence of Magenta and Tannin on Blood-corpuscles. 63 



in the cell-wall, when the corpuscles were treated with magenta*. 

 The presence of a central nucleus in these classes caused the ma- 

 cula to be invisible more frequently than in mammalia, inasmuch as 

 it suffered eclipse when situated over or under the central nucleus. 



In the fowl, dace, and minnow it was found easy to bring out the 

 parietal macula ; in the fish two spots were not unfrequently seen. 

 The macula was situated indifferently on any part of the periphery ; 

 and sometimes it projected from the surface. When happily pre- 

 pared, the specimens were even beautiful. The central nucleus was 

 dyed of the finest red ; and on the delicate outline of the cell-wall 

 hung the red parietal macula, offering a not altogether fanciful re- 

 semblance to the astronomical figures representing the moon coursing 

 in its orbit round the earth. 



At this stage of the inquiry it was conceived that an improved 

 demonstration might be obtained by fixing the dye with a mordant, 

 and then subjecting the corpuscles to a lavatory process, so as to get 

 rid of the floating granules which so much interfered with the view. 

 For this purpose a solution of tannin (which is one of the mordants 

 for magenta used in the arts) was employed ; and some advantage 



Fiff. 2. 



2--— 



Human blood after the action of tannin. 



a. Double pullulation. 



b. b. Hooded modification. 



c. Outline of the cell seen continuously through the pullulation. 



d. Bursting of the pullulations independently of destruction of the cell. 



* In order to bring out the best results, it was found requisite to modify the 

 strength and quantity of the solution for the different kinds of blood. This 

 doubtless depended upon the varying densities of the liquor sanguinis and cell- 

 contents in different animals. 



