46 SOUTHERN CALIFORNIA ACADEMY OF SCIENCES 
any part of the body is subject to more or less hypertrophy or 
overgrowth. For practical purposes a hypertrophied condition 
means not only an increase of the part in size, but also in 
function, while the term tumor means an increase in size with 
no corresponding increase in funetion. <A forcible illustration 
of these two conditions may be drawn from a normal and an 
abnormal accumulation of fat. Even a normal accumulation 
of fat may be very much localized, as when, for instanee, it 1s 
chiefly confined to the omentum, but however localized a nor- 
mal accumulation of fat may be, it is readily utilized when 
demanded by the necessities of the body, but a hpoma or fatty 
tumor remains practically unaffected by the needs of the body, 
even if these needs press to the point of starvation. 
A hypertrophied gland is capable of more functional ac- 
tivity than a strictly normal gland, as, for example, the highly 
hypertrophied mammary gland of the domestic cow compared 
with the strictly normal gland of the buffalo cow, while a 
gland enlarged by an adenoma—a gland hke tumor—is never 
more active and usually much less active than a strictly normal 
gland. 
Pathologists recognize two distinct kinds of tumors, those — 
which are formed from epithetical cells and those which are 
formed from connective tissue cells. Cancers belong to the 
first class. 
Tumors of both classes closely resemble normal tissue in 
their nutrition, and they usually have about the same nerve 
supply. As the tumor increases in size, the blood supply is 
more or less affected and thus the cells composing the tumor 
are placed in a changed environment, which quickly reacts upon 
their structure and function. 
Owing to this fact, the clear distinction between cells of 
different tissues, which exists in normal structures, becomes 
more or less obliterated and in many eases these distinctions 
become so illy defined that the positive identification of a given 
tumor becomes a matter of extreme difficulty or in some cases 
an impossibility. 
I am aware that the foregoing statements are quite out of 
harmony with the views of many writers and lecturers on 
Pathology, but I believe that the laboratory experience of 
practical workers is in harmony with the views expressed. 
