BEHE MICROSCOPE. 
Vou. VI. DETROIT, SEPTEMBER, 1886. No. 9. 
ORIGINAL COMMUNICATIONS. 
THE HUMAN TOOTH. 
Cc. H. STOWELL. 
HE following is a brief description of the structure of an 
ordinary human tooth, together with some new drawings, 
from actual specimens, to illustrate the various parts. 
A tooth may be said to be an enlarged papiela of the mouth, 
which has undergone such _ histological 
and chemical changes that it has acquired 
a remarkable degree of hardness. 
Figure 1 represents a vertical section 
of a human insisor tooth, magnified about 
twenty five diameters and reduced. All 
the parts are best seen if the specimen be 
mounted in hard balsam, after well-known 
methods. Surrounding the crown of the 
tooth is the enamel, 1, with its radial and 
concentric markings. ‘This is the hardest 
substance ot the body, and is composed 
of closely crowded polyhedral prisms. 
The dark, wavy, curved lines, running 
parallel to the surface of the dentine, are 
the brown, parallel lines of Retzius. Some 
authors attribute these lines to the pres- 
ence of pigment, perhaps oxide of iron— 
while others, including the writer, believe 
they are due simply to inequalities in the 
density of the enamel prisms The ra- 
dial markings, or the alternate light and 
dark bands, are due to the fact that the 
bundles of the enamel prisms are not all 
