ects
entirely upon their situation, malignant neoplasms wherever located
inevitably destroy life._ The clinical features of each group are in many
cases sufficiently marked to distinguish them.

MALIGNANT TUMORS.

(1) These are invariably pernicious, and from the beginning tend to destroy
life.

(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 classes 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 asserted that a true classification 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 th