38 PHYSIOLOGY. 



30. The figure on the last page represents the pulp of a 

 iiair injected ; 1, cut surface of hair ; 2, the pulp ; 3, inject- 

 ed vessel ramifying in it. The figure on the right shows 

 the hair in its fallicle, though the drawing was made from 

 the whisker of a Walrus ; 2, the cutis ; 3, external sheath of 

 the fallicle ; 4, internal sheath continuous with the cuticle ; 

 5, pulp ; 6, shaft of hair ; 7, large nerve going to it. 



31. The nails are also an appendage to the skin. Their 

 chief use seems to be to support the pulp of the finger while 

 it is exercising touch. Animals are provided with struc- 

 tures analogous in their physical and vital properties, such 

 as horns, beaks, hoofs, nails, spurs, scales, &c. Some physi- 

 ologists consider the teeth as belonging to the same class. 

 The various and peculiar functions of the skin, so important 

 to be understood in order to the preservation of the health, 

 will be fully described hereafter. 



Questions. Of what is the human body composed ? What is said 

 of the identity of solids and fluids ? What proportion do the fluids 

 bear to the solids ? How modified by age ? What purposes do the 

 fluids serve ? What is said of the solids ? How are their particles 

 arranged to form the different organs ? How are the areolae formed ? 

 Of what shape is the ultimate animal solid ? What is a primary tissue ? 

 How many primary tissues are there ? What is a filament ? a fibre 

 a tissue an organ a function ? Give an example ? What is an 

 apparatus ? a system ? membrane ? What are its uses ? What is 

 the simplest form of membrane ? its use ? What property does it 

 possess ? What its chemical composition ? What remarkable circum- 

 stance connected with it ? What is the seat of dropsy ? What varie- 

 ties of membrane are formed by the cellular tissue ? Describe the 

 adipose ? What are serous membranes ? where found ? their use ? 

 structure ? What are mucous membranes ? Describe their structure, 

 situation, use, &c. What is the skin a continuation of ? Of how many 

 parts is it composed ? What is the external layer called ? what is its 

 use ? What is the layer next ta the cuticle called ? Of what is it the 

 seat ? the next layer ? its use ? Describe the cutis vera ? What is 

 it used for ? How thick is the skin in ma-n ? By what contrivance is 

 the skin susceptible of motion ? How is the skin kept soft and pliant ? 

 What is said of the hair ? what is its structure ? what is its colour 

 owing to ? What causes it to turn grey ? What is said of the nails ? 



