MUSCULAR TISSUE. 31 
What are blood plates ? 
Minute round, colorless, discoid particles floating in blood plasma. 
Their nature and function is not well understood. 
Give the origin of red bloodcells ? 
In the embryo they are first formed in the mesoblast, and then have 
nuclei. These nucleated cells are succeeded by non-nucleated ones, 
which originate in two ways: 
First, by intracellular origin. 
Second, in the marrow of bones. 
How are red bloodcells produced by intracellular growth ? 
A part of the protoplasm in the mesoblastic ceil becomes reddish in 
color. This coloring matter collects in little globules in the cell. The 
cell elongates and joins other cells. Then small holes or vacuoles are 
formed in these cells which finally coalesce finally forming a single large 
cavity. The little globules of coloring matter enlarge and become full- 
sized red bloodcells and are now contained in these cavities. 
Describe the formation of red bloodcells in marrow. 
In red marrow are found nucleated cells smaller than marrow cells. 
These cells multiply by direct cell division or karyokinesis, their nuclei 
are colored, and the cells have the power of ameeboid motion. Finally 
the nuclei atrophy and then the corpuscle presents the appearance of a 
red bloodcell. They probably get into the blood capillaries by virtue 
of their power of amceboid movement. 
What is the origin of white bloodcells? 
First they are formed in the mesoblast. In after life it is thought 
that they are produced in lymphatic glands and tissues of a like con- 
struction. 
What are the component parts of lymph? 
A watery fluid similar to blood plasma, in which are floating nucle- 
ated corpuscles and little particles of fatty matter. The nucleated 
cella resemble the white bloodcells. The fatty matter due to digestive 
products renders the lymph milky in appearance, and it is then called 
chyle. 
= MUSCULAR TISSUE. 
What is the arrangement and function of muscular tissue ? 
It consists of fibres arranged in bundles called muscles. These 
muscles which form the flesh of animals are the means of producing 
the active movements of the body. 
