STRUCTURE OF THE BLOOD-CORPUSCLES. 31 



edgewise, as they roll over, this central prominence is rendered evident, standing 

 ont from the flattened disc. 



The action of acetic acid shows that the exterior cell-wall is connected at the 

 centre with the interior nucleus. The first action of acetic acid, which is almost 

 instantaneous, is to reverse the shape of the blood-corpuscles. They become ex- 

 panded around the periphery, whilst they remain of the same diameter at the 

 centre, thus forming an hour-glass or dumb-bell figure when viewed in profile. The 

 central portion maintains its diameter, which is that of the nucleus plus the thick- 

 ness of the attached exterior cell-wall. Generally, the swelling is greatest at the 

 extremities of the ellipsoidal disc. In some cases, the entire circumference of the 

 disc swelled, leaving a central depression, corresponding to the internal nucleus. 

 The next change effected by acetic acid, is to render the exterior cell-wall perfectly 

 transparent, and' in some cases to dissolve it completely, thus setting free the nuclei. 



Acetic acid renders the nuclei more distinct, and in many instances renders 

 visible a still smaller body, the original rudiment of the blood-corpuscle. The 

 nucleoli are situated sometimes at the centre, and at others attached to the side of 

 the nuclei. 



The blood-corpuscles of these animals, then, correspond in structure to many 

 other cells, having a cell-wall, nucleus, and nucleolus. 



The best method of viewing the action of acetic acid, is to place a drop of blood 

 upon a glass slide, and, having adjusted it to the focus of the microscope, touch its 

 border with a drop of concentrated acetic acid, and observe, under the microscope, 

 the line where the acetic acid and blood are mingling. Here we will see the blood- 

 corpuscles changing from ellipsoidal, convex discs to hour-glass or dumb-bell figures 

 and biconcave discs, and almost immediately becoming transparent, and exhibiting 

 nothing but the central nucleus with its nucleolus. I have verified these state- 

 ments by examinations of the blood of numerous Fishes, Batrachians, Ophidians, 

 and Chelonians. 



The following figures will represent in a clear light the action of acetic acid. In 

 order properly to illustrate their structure, the blood-corpuscles are represented in 

 a much rougher manner and stronger light than they appear under the microscope. 



Fia. 1. Fig. 2. 



9 / 



d(j 



@® 3 GtsM 





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Fig. 1. — Blood-corpuscles of Hammer-head Shark (Zijgsena malleus) in their normal condition. Mag. 210 diameters. 

 Fia. 2. — Blood-corpuscles of Hammer-head Shark (Zygsena malleus) treated with a drop of acetic acid, showing the 

 different stages of its action. Mag. 210 diameters. 



