. Compendium of histology. Histology. 46 FOURTH LECTURE. in water of all the tissues of the body ; it contains only per cent, of solid constituents, of which a part must still be referred to a delicate pellicle surrounding and permeating the whole. And yet the origin of the cartilage and corpus vit- reum are similar. We again meet with rounded, indifferent cells with a homogeneous, intercellular substance. In car- tilage (Fig. 23) the latter early solidifies ; in the vitreus it becomes watery and swells up, so that in a human embryo of four months (Fig. 46) the protoplasmatic cells, meas-
. Compendium of histology. Histology. 46 FOURTH LECTURE. in water of all the tissues of the body ; it contains only per cent, of solid constituents, of which a part must still be referred to a delicate pellicle surrounding and permeating the whole. And yet the origin of the cartilage and corpus vit- reum are similar. We again meet with rounded, indifferent cells with a homogeneous, intercellular substance. In car- tilage (Fig. 23) the latter early solidifies ; in the vitreus it becomes watery and swells up, so that in a human embryo of four months (Fig. 46) the protoplasmatic cells, meas- uring to mm., are separated by considera- ble intermediate gelatinous tissue. The latter gives the reaction of mucous sub- man^A^Ti5SUe °f ^ vltre°US b°dy °f 3 hU" stance or mucin, that sub- stance with which we have already become acquainted (p. 36), as a product of the meta- morphosis of the epithelial cells. For this reason our tissue has already been given the name of mucous tissue. In the vitreus of the mammalia after birth, the formative cells become arrested, and, widely separated by the interven- ing gelatinous tissue, are only with difficulty recognized. A higher development of the gelatinous tissue is consti- tuted by the so-called enamel organ of the progressing tooth. The teeth, as is known, are formed and concealed in the jaws ; the crown is first formed and the root last. The former is covered, at its commencement period, by a cap or bell-shaped structure, from the concave under surface of which the for- mation of the enamel takes place. Hence the name. Here (Fig. 22) we meet with a net-work of delicate, nucle- ated stellate cells with a varying number of processes. Some- thing like a cell division ib) is occasionally seen. The meshes are filled with a homogeneous gelatinous tissue containing mucus. The same condition prevails, at an early period, in the Whartonian jelly of the umbilical cord. Later, we meet, in. Please note that these image
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