GERMINAL MEMBRANE. 51 
a milk-white colour to the fluid. These granules, which are 
of various size, resemble milk-globules, and, as has been fre- 
quently remarked by others, exhibit also like them a brisk 
molecular motion. In consequence of the speedy action of 
water upon these globules, they must be examined in albumen 
or a weak solution of common salt, which preserves them better. 
These fluids also do not impart a white colour to the surface of 
a yelk which is opened in them, as water does. The globule, 
when crushed under the compressorium, tears somewhat sud- 
denly on one side, the other margins remaining smooth, and 
then, without any increase of the pressure, a large quantity of 
the globules contained in it flow slowly forth. This fact indicates 
an external membrane belonging to the globules, but it must be a 
very soft and delicate one.. Baer, who distinguishes four kinds 
of them, believes that he has also sometimes seen such a mem- 
brane in the yelk-globules of immature ovarian eggs. The 
yelk-globules when isolated are round, but, in their natural 
position in the yelk, they flatten against one another into 
angular shapes, in which manner the crystal-like bodies observed 
by Purkinje in the boiled yelk are produced. These bodies 
generally make up the whole of the true yelk-substance of a 
fresh egg, so that, with the exception of the contents of the 
yelk-globules, we do not usually meet with any free granulous 
substance in the yelk. The minutely granulous substance 
which is observed in addition to the yelk-globules, particularly 
after the action of water upon them, appears in most instances, 
and on the external layers of the yelk invariably, to be produced 
solely by the destruction of the yelk-globules. In the vicinity 
of the yelk-cavity of a boiled egg, however, we frequently find 
a coagulated substance composed of granules similar to those 
contained in the yelk-globules, and which appears to be actually 
free yelk substance not enclosed within globules. 
It is necessary to examine the eggs while still contained in 
the ovary, if we wish to become acquainted with the process of 
formation of these two kinds of globules (those of the yelk- 
cavity and yelk-substance), and the mode of production of the 
yelk-cavity and its canal. The younger eggs, having a diameter 
of one or two lines, have a grayish-white colour, but are not 
yellow ; if such an one be cut through the centre, under water, 
it is found to contain a thick, semi-fluid, grayish-white mass, 
