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XXIII. Researches in Embryology. Third Series : A Contribution to the Physiology 
of Cells. ' By Martin Barry, M.D., F.R.S., F.R.S.E., Fellow of the Royal 
College of Physicians in Edinburgh. 
Received April 18, — Read May 7, 1840. 
The “Second Series” of these Researches-f' traced certain changes in the mamtni- 
ferous ovum consequent on fecundation. It is the object of the present communica- 
tion to describe these changes more minutely, as seen by the aid of powerful lenses ; 
and to make known a remarkable process of development thus discovered. 
In order to obtain more exact results, my observations were still made on the same 
animal as before, namely, the Rabbit, in the expectation that, if these labours were 
successful, it would be comparatively easy to trace the changes in other Mammals. 
By pursuing the method of obtaining and preserving ova from the Fallopian tube, 
which I recommended in my last paper, I have been enabled to find and examine 137 
more of these delicate objects; and have thus had ample opportunity for confirming 
the principal facts therein stated. I have now procured in all 230 ova from the Fal- 
lopian tube. But being aware that repeated observations alone are not complete in 
researches of this nature, unless extended to the very earliest stages, I again specially 
directed my attention to the ovum still within the ovary, with a view to discover its 
state at the moment of fecundation, as well as immediately before and after. 
(The measurements throughout this paper, as in former ones, are stated in fractions 
of a Paris line, and thus expressed As a simple mode of reducing this fraction 
into (what is very nearly) the equivalent fraction of an English inch, I recommend 
multiplying the denominator of the former by ll^^. The actual sizes of the ova 
are represented at the foot of each Plate. To admit of comparison in size, great care 
has been taken to preserve a fixed scale in the figures, as well for the contents of the 
ova as for the ova themselves ; this being for the most part 100 diameters. In a few 
instances 50 diameters have been used ; and for parts of ova, figured separately, 300 
diameters. The Plates have been explained (par. 430.) with considerable minuteness, 
in order to admit of details being as much as possible avoided in the memoir.) 
322. I am not aware that we hitherto possess any drawings of ova from the ovary, 
either as prepared for fecundation or showing its effects. In this memoir Plate XXII. 
f Philosophical Transactions, 1839, Part II. p. 307. 
} See the “ Table of Measurements ” (par. 429.). 
MDCCCXL. 3 Y 
