NUTRITION. bd 
senses of touch and smell. Imbedded in the cutis are the sweat-glands,! 
which separate from the blood the fluid which appears on the skin when 
one is heated. These glands send forth their fluid by ducts? or canals 
of a spiral form. Besides these glands, there are, in the cutis, two kinds 
of follicles or ‘little bags’ connected with the hair. These are the hair “ 
follicles proper, which are little pits in the cutis, in which the roots of the“ 
hair are developed; and the sebaccous* follitles. which are glands for the 7 
—_—_ 
secretion of a fatty matter supplied to the ae when it comes above the 
skin, to pe its being too much dried up. Each hair consists of a 
‘bulb’ and a ‘shaft ;’ and the shaft, again, consists of a soft, pith-like part 
in n the middle, with an outer and harder layer. The bulb consists of a mass 
of the cells of which the cutis is composed, developed at the bottom of 
the follicle. The imside of the shaft contains something of the same 
kind ; while its outer layer is simply these cells dried and turned into 
a scaly nature. This is, in fact, exactly the composition of the epidermis; 
the cells which are on the surface are dried and flattened into scales (as 
seen in the scurf thrown off the skin of the head, especially under. 
the hair), so as to form a transparent, insensible Saari for the sensitive 
cutis. So, too, the nails are-formed; the horny substance of which they 
consist being composed of these ae and hardened cells, which are 
being continually pushed outward by a development of fresh cells at the 
root of, and under, the nail. 
Nutrition. 
Having described the framework of the body, we now proceed to 
consider the manner in which it is kept in repair. When anything is 
said to be kept in repair, it is understood that it is already made or 
formed ; and so here it is understood to be a full-grown human body 
that is to be nourished. And this process is different from either 
‘orowth’ or ‘development. Development is the process by which 
each part of the body is first formed or so changed as to be adapted 
to perform a higher function. Growth, again, is the mere increase, prin- 
cipally in size and weight, without any change in form, of the different 
parts by the addition of matter similar to that composing them. During 
the whole period of life, there is continually going on in all parts of the 
body a process of decay, and the casting off of substances which have 
become useless and even positively injurious in the economy of the body. 
Nutrition, then, includes the different processes of Digestion, Absorption, 
Secretion and Excretion, Circulation of the Blood, and Respiration, by 
1A gland is an organ, having blood-vesscls, absorbents, and nerves, for secreting a certain 
fluid from tle blood. 
2 From Latin duco, to lead. . 3 Latin folliculus, diminutive of follis, a bag. 
4 From Latin sebum, fat. 
s 
