TRANSACTIONS. 
On the Circulation in the Tadpole. 
By W. U. Whitney. 
(Read June 13tli, 1861.) 
1 HAVE been surprised at the comparatively small number 
among the many who^ in the present clay^ devote a good deal 
of time to the microscope^ who have examined the tadpole. 
But I am sure that not one among those who have done so 
will easily forget the sense of surprise and delight felt on 
first looking through the transparent cabinet of this little 
creature^s curiosities. He reveals to us_, through the eye of 
the microscope,, the greater part of his entire mechanism in 
living and liveliest operation, the contemplation of which 
never fails to excite equal astonishment and pleasure. 
I had often examined the tadpole under the single micro- 
scope, but on looking at him under the binocular I was aston- 
ished at the additional grasp, as it were, of vision — a power 
of penetration as well as distinctness — given by this instru- 
ment; and felt convinced that, with this great addition to 
our means, we might obtain a more complete view of the 
organism, and of the circulation especially, than had yet been 
attained. In conjunction with my friend, Mr. Fitzgerald, 
and with his binocular microscope, I began the series of 
observations which have produced the accompanying dia- 
grams, wherein the complete circle of the circulation is 
represented. As in the best English standard work on 
comparative physiology (I mean Dr. Carpenter's) — a work 
enriched from foreign as well as native sources — there is no 
such complete representation, we have presumed that the 
binocular microscope has enabled us to obtain, for the first 
time, a clear and comprehensive view of the tadpole^s vascular 
system. 
Placing the tadpole on liis back, we look, as through a 
pane of glass, into the chamber of the chest. Before us is 
the beating heart, a bulbous-looking cavity, formed of the 
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