HISTOLOGY. 
Of what does Histology treat? 
For our present purpose histology may be regarded as treating of 
the minute structures of tissues and organs of man. 
What are the structural elements of the body ? 
Cells, fibres, and intercellular substance. 
From what do these elements originate ? 
From the development of a single nucleated cell or ovum. 
CELLS. 
Describe the human ovum. 
It is a small spherical vesicle of about t}5 inch (2 mm.) in diam- 
eter, with a covering called the Zona pellucida or Zona radiata. 
Within the covering is a spherical mass called the Germinal vesicle, 
Within this isa smaller body called the Germinal spot. 
Considering the ovum as a typical cell, what would its different 
parts be called ? 
The Zona pellucida would correspond to the cell-wall. 
The Vitellus would correspond to the cell-body. 
The Germinal vesicle would correspond to the nucleus. 
The Germinal spot would correspond to the nucleolus. 
What parts corresponding to parts of the ovum or primary cell are 
always present in animal cells ? 
The cell-body and the nucleus, which is a minute vesicular structure 
contained in the cell-body. 
What parts are usually absent ? 
Cell-wall and nucleolus. Very few animal cells having either 
structure. 
What is the structure of the cell-body ? 
It is made up of an albuminoid material called protoplasm. Under 
the microscope this may appear clear or homogeneous, finely granular, 
or even reticulated. 
2—H.P.B. 17 
