Page:Microscopicial researchers - Theodor Schwann - English Translation - 1947.pdf/78

THE OVUM AND part of which flows slowly out. Around this mass lies a more consistent, cohering, membrane-like stratum, which lines the cavity of the little egg. When a portion of this mass is examined under the microscope, a great many round and very transparent vesicles or cells are observed in it, each of which encloses a dark corpuscle resembling an oil-globule. Many such globules float about free, and in addition to them there is also a good deal of minutely granulous substance present. In order, however, to examine this mass in a perfectly natural condition, the use of water must be avoided; one of the little eggs, of from half a line to a line in diameter, should be placed upon the dry object plate, and then pierced, a drop of its contents being allowed to flow out. This drop will be found to consist entirely of very pale cells, most variable in size, each one containing a round globule, the size of which is about proportionate to that of the cell. This globule or nucleus resembles an oil-globule, in consequence of its dark outline, (see pl. II, fig. 3.) Many of these cells with their nuclei are so small, that, when lying close together, they might be regarded as a merely granulous substance; the cells may, however, be recognised with a favorable light. Some of the larger ones occasionally contain two or three of the globules or nuclei before mentioned. The contents of the cells are usually quite transparent, but some isolated ones are seen, in which a minutely granulous precipitate has formed. These cells are enclosed within the egg, in a small quantity of transparent fluid. In order to explain the somewhat variable appearance which the contents of the egg assume after contact with water, a small one should be placed upon a glass with a drop of that fluid, and some of its contents pressed out whilst under the microscope. A quantity of these cells will then be seen to burst quite suddenly in the water, precisely like soap-bubbles in the air. In consequence of their paleness, the fact of the bursting is rendered manifest, in the first instance, only by the sudden motion of the nucleus, which, together with some minutely granulous substance, remains behind. If these cells were solid, although ever so soft, this sudden bursting would not be possible. They are therefore true cells. I cannot say whether the globule enclosed in them is to be regarded as the nucleus. Although it resembles an oil-globule, it does not appear to be fat; for if acetic acid be