In studying this subject, it will be necessary to examine the different structures of organized bodies, and to understand their mechanism, as the mechanist understands a machine, before we shall be able to ascertain the kind of power by which they are moved.

On viewing the human frame, we find it covered with a membranous complex structure called the skin Besides three membranes which are classed under the general term skin or integuments, there are found in it innumerable minute globular bodies called papillary glands. These little globate bodies are found to be highly organized, having minute arteries terminating, and minute veins commencing in their structure. They are found aisc, oy means of magnifying glasses of great power, to have minute ducts issuing from them, and terminating every where with open orifices on the surface of the skin, as seen at e, fig. 1.

On an examination of the organs, as the brain, eyes, heart, lungs, liver, spleen, pancreas, kidneys, cystis, uterus, stomach, and intestines, we find them all, without a solitary exception, covered with a kind of skin called a serous membrane, in which is inclosed an incalculable number of minute glands or elementary organs, with ducts terminating in open orifices on the surfaces of these membranes, like those of the common covering of the body. The glands of both structures are found, on an examination of the orifices of these ducts, to excrete an aqueous or watery fluid by which these surfaces are constantly maintained in a humid or moist state. The great quantity of this fluid seen running off from the skin, and its accumulation in the cavities containing the organs, when these glands are excited to inordinate action, attest both the perfection of their mechanism and their fitness for their specific use.

If we now proceed to examine the membrane which lines the internal parts of the body, we shall find it, with slight modifications, characterized by the same structure as the serous membranes. This modification principally consists in its having what is called a villous, instead of a serous surface, like the serous membranes. We find the whole tract of the alimentary canal, including the mouth, æsophagus, stomach, and intestines, lined with this membrane, as well as the internal parts of every

MOTIVE POWER

OF THE

HUMAN SYSTEM,

WITH THE

SYMPTOMS AND TREATMENT

OF

CHRONIC DISEASES.

FOURTH EDITION.

BY H. H. SHERWOOD, M. D., 325 BROADWAY, N. Y.

NEW-YORK.

expand, while those on the outside contract with equal force. One end of each of these muscles is attached to the lower part of the bone belonging to the upper part of the arm, called the humerus, and the other ends are attached to the lower end of the bones of the lower part of the arm, near the wrist, called the ulna and radius; so that while the lower part of these bones is pushed on one side, when the muscles of that side are expanded, it is pulled at the same time on the opposite side, when the muscles on that side are contracted; and thus motion is produced by the simultaneous action of these muscles.

Now it is a remarkable fact, that every one of these four hundred and thirty-six muscles which thus produce motion in different parts of the body, is covered with a membrane, the outer surface of which has a serous, and the inner side a mucous surface; hence these membranes are called muco-serous membranes. All these different surfaces, then, like those of the skin and membranes of other parts of the body, are covered with different kinds of matter, presenting together immense surfaces, from which constantly issue two forces of different kinds.

The reader who has seen a common galvanic battery, cannot fail to observe that this arrangement of surfaces corresponds with that of the different metallic surfaces of the battery. He will also notice that these forces thus maintained on these membranous surfaces, exactly correspond with those necessarily maintained on different surfaces of the battery. The two forces are conducted from the two metalic surfaces to the poles of the battery by two metallic wires, and if we can now find conductors to convey the forces from the skin and different membranous surfaces to poles, the resemblance will be complete and satisfactory.

In pursuing this object we first find numerous minute threads, called nerves, penetrating the little glands of the skin, surfaces and mucous membranes, and every fibre of a muscle. On tracing these nerves, we see them uniting together and increasing in size in proportion to the distance from these surfaces, and at length conjoining with the spinal cord. The spinal cord is formed into four columns, united first with a broad base,

and then with the brain.

These forces are therefore conducted from the skin and membranous surfaces and concentrated in the brain to form poles, or a motive power to put in motion this apparently complicated yet really simple machinery. This structure, arrangement and order of the different parts of the human body were well known to Malpighi, Ruych, Halier, Hunter and Bichat, and are recognized by every anatomist of the present age, and now present to our view a Galvanic Battery altogether superior to any ever made by man.

The cut. fig. 2, gives a general view of the nerves of the limbs, of the

spinal cord, and of the connexion of the spinal nerves, all of which are well known to be good conductors of the Galvanic forces.

We will now examine the construction of the brain and see if we can find the situation of the magnetic poles. The upper part of the brain called the cerebrum, is divided by the longitudinal sinus from A to B,

into two hemispheres as seen in the figure, A being the front and B the back part of it. The whole presents a convoluted surface, the sulci or furrows of which extend into it a distance from a line to an inch, and thus separate more or less the convolutions, or phrenological organs of the brain. This figure was copied very accurately by Dr. Anderson of this city, from a cast of the brain by L. N. Fowler. The general form and direction of the convolutions are very regular and constant, in the human brain. Yet the form of the convolutions are different in the different hemispheres as seen in the figure;-one of them being a positive and the other a negative hemisphere.

On turning the brain over or reversing its position we find on its under surface an apparently complicated structure surrounded by convolutions, as seen in fig. 4.