SCIENTIFIC SUMMARY. 
oak 
oyo 
interesting and important discoveries and observations which have been 
recorded — the crowd of intelligent observers being, on the one hand, so nume- 
rous, and on the other the space afforded in these pages being necessarily so 
restricted. 
It will be best, therefore, to adopt as systematic a plan as possible, and we 
propose to divide the subject of microscopic research into animal, vegetable, 
and mineral ; while any improvements or advances made in the microscope 
itself will not be lost sight of. 
The advantages of the binocular microscope, upon which we dwelt in a 
previous article, are becoming generally appreciated, and a writer in the 
Quarterly Journal of Microscopical Science (Mr. W. U. Whitney) speaks in 
raptures of the new views of circulation in a little tadpole unfolded to his sight 
by the magical instrument. Having ingeniously rendered the little tadpole 
unusually transparent by a low diet, consisting of clean water only, Mr. Whitney 
was enabled to trace the direction of the course of the larger vessels ; and was 
also favoured with a specimen, unusually transparent, which gave admirable 
views of its internal economy. We have not space to trace here the whole 
circulatory system in the tadpole, but wish rather to call attention to the 
interesting results at which the observer arrives. The first large artery which 
arises from the heart (the cephalic) supplies the head, but also “ receives into 
it small branches from the subdivisions of the pulmonary artery, so that 
there is a direct communication between these two vessels.” The second 
(pulmonary) trank is devoted to the lung, for purposes of aeration solely ; and 
the third (aortic), in its passage to the abdomen, inosculates with the pul- 
monary branches, and thus provision for aeration is much more completely 
made than in any reptile. The miter concludes that the liveliness and 
activity of the tadpole, so superior to that of the adult frog, are owing to this 
respiratory arrangement, on the well-known physiological principle, that 
the activity of vital functions is in proportion to the completeness of the 
aeration of the sanguineous stream which is sent from the heart to all parts of 
the body. 
The changes which the juvenile frog undergoes require indeed active respi- 
ration for their normal production. For nine days after the animal is hatched 
he has external branchiae like a fish, and requires, in this condition, to be 
placed in shallow water, not far from the atmospheric air. From the seventh 
to the ninth day these branchiae rapidly vanish, first on the right side, after- 
wards on the left ; and then the true tadpole swims apparent. Henceforth he 
requires atmospheric air for his active respiration. The question whether 
light or heat most favours the development of these changes forms the 
subject of a paper read before the Royal Society, by Mr. John Higginbottom, 
F.R.S., in January last. Numerous experiments, in which the frog’s spawn 
was placed in situations whence light was excluded, led him to the conclusion 
(contrary to that arrived at by Dr. W. F. Edwards, of Paris) that, the tempera- 
ture being sufficiently high, it mattered not whether light were present or 
absent, the ova developing with equal rapidity in either case. According to 
Mr. Higginbottom, it is the necessity for atmospheric respiration, rather than 
the presence of light, which causes the tadpoles to approach the surface, so 
that experiments, in which the tadpole were immersed in the dark some feet 
below the surface were altogether inconclusive. Pulmonary respiration takes 
