PHYSICAL ANTECEDENTS OF SCIENCE 113

of the order of apes, though widely differing from most

of them.

Such being man's place in nature as regards the structure

of his body, it remains to briefly pass in review the main

facts of that body's organization.

As everyone knows, the human frame is a very complex

structure : a mass of flesh (composed of a great number

of muscles of different sizes) embracing a skeleton and

clothed with skin the skeleton consisting of the skull,

backbone, ribs, and the bones of the two pairs of limbs.

Within the body are the heart, lungs, stomach, intestines,

liver, kidneys, etc. The skull and backbone together

enclose a mass of soft, white substance the brain and

spinal marrow or spinal cord. Delicate threads of similar

substance (nerves) and tubes of various sizes (vessels)

traverse the body in all directions.

Conditions essentially similar, but differing greatly in

various ways in different groups (thus, e.g., there may be

but two pairs of limbs or none), prevail in all beasts, birds,

and reptiles.

Organs nearly related to each other form what are

termed "systems" of organs. Thus the muscles, each of

which is made up of a mass of fibres, and are of different

shapes and sizes (muscles of the limbs, trunk, head, jaws,

etc.), constitute " the muscular system." Muscles are gener-

ally attached by their opposite extremities to different

bones. Thus, again, the mouth, stomach, and alimentary

canal, with their appendages, form the " alimentary system " ;

the heart, with all the tubes (arteries, veins, etc.) connected

with it, composes the " circulating system " ; the wind-pipe

and lungs constitute the " respiratory system " ; the organs

concerned with reproduction are the " generative system " ;

and the brain, spinal cord, and all the nerves of the body

together make up the " nervous system." These groups of

i

of the order of apes, though widely differing from most

of them.

Such being man's place in nature as regards the structure

of his body, it remains to briefly pass in review the main

facts of that body's organization.

As everyone knows, the human frame is a very complex

structure : a mass of flesh (composed of a great number

of muscles of different sizes) embracing a skeleton and

clothed with skin the skeleton consisting of the skull,

backbone, ribs, and the bones of the two pairs of limbs.

Within the body are the heart, lungs, stomach, intestines,

liver, kidneys, etc. The skull and backbone together

enclose a mass of soft, white substance the brain and

spinal marrow or spinal cord. Delicate threads of similar

substance (nerves) and tubes of various sizes (vessels)

traverse the body in all directions.

Conditions essentially similar, but differing greatly in

various ways in different groups (thus, e.g., there may be

but two pairs of limbs or none), prevail in all beasts, birds,

and reptiles.

Organs nearly related to each other form what are

termed "systems" of organs. Thus the muscles, each of

which is made up of a mass of fibres, and are of different

shapes and sizes (muscles of the limbs, trunk, head, jaws,

etc.), constitute " the muscular system." Muscles are gener-

ally attached by their opposite extremities to different

bones. Thus, again, the mouth, stomach, and alimentary

canal, with their appendages, form the " alimentary system " ;

the heart, with all the tubes (arteries, veins, etc.) connected

with it, composes the " circulating system " ; the wind-pipe

and lungs constitute the " respiratory system " ; the organs

concerned with reproduction are the " generative system " ;

and the brain, spinal cord, and all the nerves of the body

together make up the " nervous system." These groups of

i