GERMINAL MEMBRANE. 54 



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 

 i 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 rind 

 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 arc 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, 



