42 LANCASHIRE VETERINARY MEDICAL ASSOCIATION. 
becomes its efferent duct. The efferent duct ascends through the 
derma and epidermis to terminate by a funnel-shaped and oblique 
aperture or pore upon the surface of the body. These glands are 
found nearly all over the body in animals with much hair; they are 
connected with the hair-follicles, sometimes three or four to one 
follicle, but where there is little hair they come to the surface inde¬ 
pendently. Erasmus Wilson calculates that there are about twenty- 
eight miles of perspiratory tube, if each tube were added to its fellow 
on the surface of the human body, therefore pointing out to us 
the importance of cleanliness to such a system. 
The sebiparous glands are the special producing organs of the 
sebaceous or fatty secretion of the skin ; they are distributed almost 
universally over the surface of the body. The largest of these 
glands are those of the eyelids, called the meibomian glands. 
The purpose of sebiparous glands being to supply the surface of the 
skin with an oily secretion, they are found abundantly in situations 
where such a secretion is chiefly required. 
I will next proceed to describe the hair, an appendage of the 
skin. 
Hairs are horny filaments appertaining to the structure of the 
skin, and are distributed nearly all over the surface of the body. 
They are usually divided into short, long, and downy. Hairs spring 
from a follicle or hair-sac. 
Growth of hair is accomplished by the successive formation of 
new cells in the superficial portion of the papilla of the hair-follicle, 
and these cells are gradually moved onwards and converted into the 
fibrous tissue of the hair, while new cells are produced to take their 
place. All animals cast their hair at certain seasons of the year. 
This is analogous to the shedding of the epidermis of the Reptilia. 
The colour of the hair depends upon the amount and colour of the 
pigment it contains, and not in the amount contained in the skin. 
It is said to be present in the fibrous portion of the hair. The 
strength also dwells in this fibrous part, for hairs deficient in this 
structure are remarkable for their brittleness. I shall next proceed 
to the physiology of the skin. 
Physiology of the Skin. 
Wilson says that in a physiological point of view the skin is an 
organ of sensation, absorption, and secretion. In the former capa¬ 
city it supplies us with knowledge, afibrds us gratification, and warns 
us of the presence of injurious or destructive agents. By means of 
the second it is enabled to appropriate the fluids contained in the 
surrounding medium, and perform the ofiice of a respiratory organ. 
And by means of the third it provides for its own softness and 
pliancy, regulates the influence of temperature, both external and 
internal, and acts as an important depurating organ of the blood. 
As an organ of sensation it endows us with the function of touch, 
of determinating the qualities of objects by their properties of re¬ 
sistance, of extent, and variety of surface. It enables us to dis¬ 
tinguish between hard and soft, smooth or rough, hot or cold. 
