96 
POPULAR SCIENCE REVIEW. 
confine ourselves to stating — in opposition to Dr. Phipson’s allegations — 1. 
That the phyllosoma is not the larva of the craw-fish, 2. That the produc- 
tion of neuter aphides is not to be explained on Dntrochet’s views, 3. That 
the Echinodermata and Bryozoa do not belong to the division (?) Polyps. 4. 
That the class Khozopoda is not higher than Infusoria. 5. That the gastropod 
and bivalve mollusca are not all hermaphrodite. Excepting those trifling- 
errors which, after all, anyone not an original observer might easily be led 
into, Dr. Phipson’s work is very carefully compiled, and will be profitably 
read by all who are interested in the subject of practical zoology. 
SIGHT AND TOUCH.- 
philosojDhy of vision is, whether considered as a physiological or a 
- 1 - psychological subject, about one of the most obscure and difficult of 
all departments of science. It would therefore be beneficial to exact know- 
ledge, that all questions relating to it should be fairly and impartially 
discussed. Whether Mr. Abbott has fulfilled these conditions, we shall not 
say, but at all events he has drawn attention to some very serious difficulties 
in the way of accepting Bishop Berkeley’s theory of vision. It is necessary 
to explain to our readers the nature of the question at issue between the 
great bulk of physiologists and Mr. Abbott. How do we judge by the aid 
of the eye of the distance which any object is from us ? Present-day phy- 
siologists, acknowledging the accuracy of Berkeley’s reasoning, say : by 
association with the ideas derived from our tactual or touch impressions of 
these same objects. That is to say, we look at an object, and in order to 
estimate its distance we make a mental and rapid comparison of its distinct- 
ness and illumination with those of some object whose exact existence we have 
ascertained by experience. Hence it follows, from this view, that in the first 
instance, in early life, a standard of length is framed by practice ; such, for 
example, as the time it requires, by means of bodily exertion, to reach some 
object, would enable us to institute. Similarly when conceiving of the form 
of a body, we contrast it with results which have been already derived from 
the exercise of the sense of touch. In proof of which latter, there are many 
instances on record of blind persons suddenly restored! o sight, who were, for 
some time subsequent to the restoration of vision, compelled to judge of 
distance and form by touch, till they had sufficiently associated the sensations 
arising from the combined exercise of the two faculties. Now it is against 
this long-received doctrine, that our author has waged war ; and we think 
that although his pleading will hardly accomplish the result he aims at, there 
is nevertheless much force in his arguments, and a very considerable deal of 
erudition and careful study evidenced by his writing. He suggests that the 
eye has, independently of the other senses, the power of judging of distance 
by certain involuntary motions of its own. It is extremely difficult to make 
out clearly what it is that Mr. Abbott means ; for his style is charac- 
terized by a metaphysical tone, which would certainly engender in the 
“ Sight and Touch ; or, an Attempt to disprove the received (or 
Berkeleian) Theory of Vision.” By Thomas K. Abbott, M.D., F.T.C.D., &c. 
Pp. 178. London : Longman & Co. 1864. 
