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REVIEWS OE NEW PUBLICATIONS. 
Analogies may be carried too far, and science by their means made fanciful, the 
allusions to them being hardly needed where no philosophical deduction can be 
drawn, or practical application made. Analogy of structure is important in 
similar objects, as it may point out a community of function; it is also important 
when it can be traced in a series of objects connecting the higher and lower 
members by a common indication; but when analogies in the form or disposition 
of matter are pointed out between remote objects, they can hardly be useful. 
We allude here to the analogy between the spiral vessels of the vascular tissue of 
plants, and the tracheae of animals, which our author has insisted on more than 
once in his volume. This is a favourite analogy of the French naturalists, and 
some of them have even named the spiral vessels tracheae. We cannot stop here 
to point out the want of intimate analogy between these organs, but the difference 
between the lowest form of animal in which we find tracheae, and the plants in 
which spiral vessels exist, must be evident to all. 
In the fjrst book the subject of General Physiology is discussed, and the 
influence of external agents upon life is considered. The third chapter is devoted 
to an exposition of the general laws of organic development, and we have no 
hesitation in saying that it is one of the best digests of the subject in our 
language. We would especially direct attention tohhis part of Mr. Carpenter’s 
volume/as it is too often supposed that the sciences of Botany and Zoology, 
including the functions of life, are but a mass of details, that are at present too 
little understood to admit of the application of any general expressions in the 
form of laws. But the principles that have already been laid down lead us to 
hope that the time is not far distant when the laws of organic life shall be 
expressed by terms as simple as those which combine together the varied pheno¬ 
mena of inorganic masses, when the question of Cuvier shall be answered, and 
Natural History shall glory in the possession of 66 its Newton.” 
The author’s remarks on the doctrine of a vital principle are very judicious. 
He condemns the use of the term vital principle, as expressing the cause of certain 
phenomena which are observed in organic bodies, but thinks there might be no 
peculiar objection to the use of the term as a convenient expression for the sum 
of the unknown powers which are developed by the action of vital properties. 
The use of the term principle in science generally is exceedingly vague and 
unsatisfactory, but when applied to the phenomena of life, is a peculiarly fertile 
source of erroneous views and conclusions, and if not abandoned altogether, ought 
only to be used under obvious restrictions. 
We could have wished to have followed our author through many of the 
interesting topics which are discussed, with a masterly hand, in this part of his 
book, but our limits forbid. In the second book he enters on the subject of 
Special and Comparative Physiology. This part of the volume embraces the 
