70 ORGANISED FLUIDS. 



circulation of the blood, from its extraordinary elasticity and 

 transparence. For a knowledge of this fact science is 

 indebted to a neighbour and friend of mine, Dr. A. Waller, 

 and by whom it was communicated some years ago to M. 

 Donne. For the exhibition of the circulation in the tongue 

 of the frog, in a satisfactory manner, it is necessary that the 

 animal should be secured in the, following way : A bandage 

 having been passed several times around the body of the 

 frog, so as to secure effectually the anterior extremities, it is 

 next to be fastened to a piece of cork by additional turns 

 of the bandage : this piece of cork should be very thin, six 

 or seven inches in length, by about ten in width, and per- 

 forated at one extremity by a square aperture, the diameter 

 of which should not be less than two thirds of an inch. To 

 the margin of this aperture, the mouth of the frog, in binding 

 it to the piece of cork, should be brought. The frog having 

 been thus effectually secured, the soft and pulp-like tongue 

 should be drawn out of the mouth by means of a pair of 

 forceps, and being spread over the surface of the aperture, 

 should be retained in position by from four to six pins, the 

 elasticity of the tissue of the tongue allowing of its extension 

 into a thin and transparent membrane with but little risk of 

 a rupture of the organ ; lastly, the piece of cork should be 

 fastened to the stage of the microscope, in such a position 

 that the tongue rests over the opening in the stage. These 

 preliminary arrangements being effected, and a low power 

 of the microscope being brought to bear upon it, a spec- 

 tacle of the highest interest and beauty is revealed to the 

 sight of the beholder. We have displayed before us, in 

 action, almost every tissue of the animal organisation, in its 

 simplest and clearest form and disposition arteries, with 

 their accompanying veins and nerves ; muscular tissue ; the 

 blood, with its red and white globules ; epithelial cells ; 

 glands of the smallest possible complication of structure : and 

 these several parts are not merely visible, but their form, 

 disposition, construction, and normal mode of action, are all 

 distinctly apparent; the blood ever flowing, the muscles 

 contracting, and the glands secreting. 



