Part 2 (1/2)

2d. The free communication between the cells is still more remarkable in regard to air. Sometimes, when an accidental opening has been made from the air-cells of the lungs into the contiguous cellular tissue, the air in respiration has penetrated every part until the whole body is so inflated as to occasion suffocation. Butchers often avail themselves of the knowledge of this fact, and inflate their meat to give it a fat appearance.

31. ”Although this tissue enters into the composition of all organs, it never loses its own structure, nor partic.i.p.ates in the functions of the organ of which it forms a part. Though present in the nerves, it does not share in their sensibility; and though it accompanies every muscle and every muscular fibre, it does not partake of the irritability which belongs to these organs.”

32. Several varieties of tissue are formed from the cellular; as, the _Serous_, _Dermoid_, _Fibrous_, and several others.

33. The SEROUS TISSUE lines all the closed, or sac-like cavities of the body; as, the chest, joints, and abdomen. It not only lines these cavities, but is reflected, and invests the organs contained in them.

The liver and the lungs are thus invested. This membrane is of a whitish color, and smooth on its free surfaces. These surfaces are kept moist, and prevented from adhering by a _serous_ fluid, which is separated from the blood. The use of this membrane is to separate organs and also to facilitate the movement of one part upon another, by means of its moist, polished surfaces.

Give observation 2d. 31. What is said of the ident.i.ty of this tissue?

32. Name the varieties of tissue formed from the cellular. 33. Where is the serous tissue found? What two offices does it perform? Give its structure. What is the use of this membrane?

34. The DERMOID TISSUE covers the outside of the body. It is called the _cutis_, (skin.) This membrane is continuous with the mucous at the various orifices of the body, and in these situations, from the similarity of their structure, it is difficult to distinguish between them.

_Observations._ 1st. In consequence of the continuity and similarity of structure, there is close sympathy between the mucous and dermoid membranes. If the functions of the skin are disturbed, as by a chill, it will frequently cause a catarrh, (cold,) or diarrhoea. Again, in consequence of this intimate sympathy, these complaints can be relieved by exciting a free action in the vessels of the skin.

2d. It is no uncommon occurrence that diseased or irritated conditions of the mucous membrane of the stomach or intestines produce diseases or irritations of the skin, as is seen in the rashes attendant on dyspepsia, and eating certain species of fish. These eruptions of the skin can be relieved by removing the diseased condition of the stomach.

35. The FIBROUS TISSUE consists of longitudinal, parallel fibres, which are closely united. These fibres, in some situations, form a thin, dense, strong membrane, like that which lines the internal surface of the skull, or invests the external surface of the bones.

In other instances, they form strong, inelastic bands, called _liga-ments_, which bind one bone to another. This tissue also forms _tendons_, (white cords,) by which the muscles are attached to the bones.

_Observation._ In the disease called rheumatism, the fibrous tissue is the part princ.i.p.ally affected; hence the joints, where this tissue is most abundant, suffer most from this affection.

34. Describe the dermoid tissue. What is said of the sympathy between the functions of the skin and mucous membrane? Give another instance of the sympathy between these membranes. 35. Of what does the fibrous tissue consist? How do these appear in some situations? How in others?

What tissue is generally affected in rheumatism?

36. The ADIPOSE TISSUE is so arranged as to form distinct bags, or cells. These contain a substance called _fat_. This tissue is princ.i.p.ally found beneath the skin, abdominal muscles, and around the heart and kidneys; while none is found in the brain, eye, ear, nose, and several other organs.

_Observation._ In those individuals who are corpulent, there is in many instances, a great deposit of this substance. This tissue acc.u.mulates more readily than others when a person becomes gross, and is earliest removed when the system emaciates, in acute or chronic diseases. Some of the ma.s.ses become, in some instances, enlarged.

These enlargements are called _adipose_, or _fatty tumors_.

[Ill.u.s.tration: Fig. 4. 1, A portion of the adipose tissue. 2, 2, 2, Minute bags containing fat. 3, A cl.u.s.ter of these bags, separated and suspended.]

37. The CARTILAGINOUS TISSUE is firm, smooth, and highly elastic.

Except bone, it is the hardest part of the animal frame. It tips the ends of the bones that concur in forming a joint. Its use is to facilitate the motion of the joints by its smooth surface, while its elastic character diminishes the shock that would otherwise be experienced if this tissue were inelastic.