Part 39 (1/2)

(2) The cellular element predominates; therefore they grow rapidly.

(3) Possessing no capsule, they infiltrate surrounding tissues.

(4) They infect adjacent lymph glands.

(5) They recur even after complete removal.

(6) They give metastasis; that is, they become disseminated in different organs.

(7) Their presence develops a progressive emaciation.

BENIGN TUMORS.

(1) These in and of themselves do not tend to produce death.

(2) As the cellular element is not liable to predominate, they grow slowly.

(3) They are encapsulated, and when diffuse do not infiltrate surrounding tissues.

(4) They do not infect adjacent lymph glands.

(5) They do not recur after complete removal.

(6) They do not manifest metastasis.

Benign tumors, though harmless, may, by the accident of their location, indirectly produce death. Mere pressure on the brain substance of an otherwise innocent tumor, compression of the blood supply for vital organs, growth in such manner as to cause obstruction in the alimentary tract or pressure upon nerves, may cause death, or, prior to death, so combine the effects of anemia (deficiency of blood), starvation, and pain, with its consequent restlessness, as to produce a veritable cachexia (condition of general ill health).

On the other hand, a malignant tumor in its primary growth may so implicate a vital organ as to destroy life before metastasis can occur or even before cachexia can develop. Thus, to the untrained observer, environment may so operate as to cause these two cla.s.ses of new growths to simulate each other. The boundary lines may seem to overlap. It is here that the microscope, as the court of last appeal, adjudicates positively in the diagnosis between these two clearly marked divisions.

It may almost be a.s.serted that a true cla.s.sification of tumors can not be made until we know more about the cause of them. The arrangement here presented is offered to meet the practical needs of the veterinarian, student, and farmer rather than of the pathologist.

We may roughly divide the tissues of the body into structural and lining tissues. The structural tissues are composed of the tissues of special function and simple connective tissues. The lining or covering tissues, both internal and external, are known as epithelium.

Section A of the table below contains the true tumors or proper neoplasms.

Section B includes the cysts, some of which are true tumors, while others are false ones, but the latter are added because of their gross resemblance to the true and the consequent necessity of considering them at the same time.

TUMORS AND CYSTS.

A.--Tumors.

BENIGN.

I.--_Tumors composed of tissues resembling those of special function._

1. Type of muscle tissue Myoma.

2. Type of nerve tissue Neuroma.

3. Type of vascular tissue Angioma.

4. Type of gland tissue Adenoma.

II.--_Tumors composed of fully developed connective tissue._