TRANSACTIONS OF T1IE SECTIONS. 
599 
1. The Development of the Ovum. 
2. The ultimate Structure of Organized Matter. 
3. Physiological Effects of Oxygen and other Gases. 
4. Experiments upon the Irritability of Animals. 
In the former part of the paper, the author, after a general 
view of the utility of the microscope, and especially of the most 
recently invented kinds, in researches into the minuter organi¬ 
zation and less obvious processes of nature, presents a connect¬ 
ed view of the changes observable in the impregnated ovum 
during its gradual development into a new being. Rejecting 
the opinion that it contains within itself the miniature rudiments 
in detail of the entire foetal fabric, and that the embryo growth 
is a simultaneous evolution of all the organs which belong to 
the future foetus,—he follows Professors Wolf, Baer, &c., in 
describing the gradual changes in the germinal membrane, and 
the successive growth of all the organs, in the ovum of the 
fowl; compares them with what is known of the parallel deve¬ 
lopment of the foetus in viviparous animals ; and insists on the 
probability that in both cases the evolutions are conducted on 
one common principle. 
In treating on the subject of the ultimate structure of or¬ 
ganized matter, the author compares the results of the exami¬ 
nation of the red particles in blood by successive observers 
from the time of Leeuwenhoeck to the present day. The su¬ 
perior power and clearness of Mr. Lister’s microscope had en¬ 
abled its inventor, with Dr. Hodgkin, to examine the blood 
and the tissues of the body to great advantage : the particles 
in human blood appeared to them as described by Dr. Young, 
— circular, but flattened, with no capsule or central nucleus, of 
a pale pink colour, and transparent; the same particles in the 
frog and skate appeared to be oval. In the muscular tissue 
the fibres, instead of being seen as in an inferior microscope, 
like so many strings of globules, appeared to be simple unin¬ 
terrupted fibrillse, longitudinally placed by the side of each 
other, and each separately crossed at right angles by a series 
of stria?. In no tissue of the animal body are distinct particles 
to be seen, and in no animal fluid are the particles strictly 
globular. 
Thus the modern improvements in the microscope afford no 
confirmation of the views of those physiologists who imagined 
the particles of blood and of other animal and vegetable fluids 
to possess the globular form and the vitality of a monad, and 
considered their concatenation in muscular fibre as the first 
step of organization. The author concludes this head by in- 
