CIRCULATION OF THE BLOOD. 
80. In fine, tlie red corpuscles, after having been fully developed 
in the circulation, are dissolved, and being converted into the 
fibrinous fiuid, pass into the other parts of the organisation, so as 
to form the different organs of the system. 
81. Next to the constitution of the blood, no subject con¬ 
nected with it is more interesting and important than its circula¬ 
tion, and we know no spectacle presented by any of the scientific 
artifices, by which the secret operations of nature are disclosed 
to our view, which excites more astonishment and admiration 
than the circulation of the blood, as rendered visible with the 
microscope. 
82. Let any one imagine an animal organ, full of every variety 
of blood-vessels of the most complex structure, into the composi¬ 
tion of which enter every form of organ: arteries, veins, capillaries, 
muscles, nerves, glands, and membranes: representing in short a 
microcosm of the whole animal organisation; and let us suppose this 
brought within the field of the microscope, so as to display, before 
the wondering view of the observer, all the complicated motions 
and operations of which it is the theatre. Such a spectacle is 
presented by the tongue of the frog, an object first submitted to 
this species of experiment by Dr. Donne, at the suggestion of a 
young Englishman, a Mr., since Dr., Waller, who was in at¬ 
tendance upon his course. The method of accomplishing this, 
with some modifications, as described in the Physiological Journal, 
is as follows:—“A piece of cork, from two to three inches in 
breadth, and six to eight inches in length, is to be procured, in 
which is to be bored, a hole of about half an inch in diameter 
midway between the sides, and about an inch and a half to two 
inches from one of its ends. In this part the piece of cork should 
be of double thickness, which is effected by joining, by means of 
marine glue, a small piece of cork upon the first piece. Upon 
this is laid the frog, previously enveloped in a linen band, or fixed 
to the cork by pins thrust through the four extremities, so as to 
prevent any great movements of its body or its feet; it is placed 
upon the back, the end of the nose abutting on the border of the 
hole. The tongue, the free end of which is directed backwards, is 
then to be drawn out of the mouth gently with a forceps, and 
slightly stretched and elongated until it reaches a little beyond 
the opposite edge of the hole, where it is to be fastened by two 
pins ; the sides are to be fastened over the hole in a similar way. 
In this state, the tongue presents the appearance of a semi-trans¬ 
parent membrane, which permits us to see through its substance ; 
and when placed between the light and the object-glass of the 
microscope, offers one of the most beautiful and marvellous 
spectacles which can possibly be witnessed. It will be found most 
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