34 BULLETIN 1449, U. S. DEPARTMENT OF AGRICULTURE 
excessive connective-tissue development increases the resistance by 
retarding at the same time the epithelial-cell proliferation. 
Besides the variation in the amount of connective tissue in the 
stroma of cancers, ranging from a mere scantiness to a conspicuous 
abundance of fibrous tissue, the stroma may undergo hyaline or 
myxomatous degeneration and become gelatinous in appearance. 
The stroma at times is very cellular, when the cancer is known as 
sarcomatous carcinoma, which is not a good term. 
Appearance. — For a time a cancer is limited to the gland from 
which it has originated and is known as primary cancer. Cancers 
do not remain long in an inactive state. They are not encapsulated 
and the epithelial cells proliferate and penetrate into the surround- 
ing tissues in the direction of least resistance, which is the course of 
the lymph vessels. It is not possible, on macroscopic inspection, to 
define the limits of the cancer from the surrounding tissues. Micro- 
scopic examination alone can determine the exact limits of the cancer 
invasion. When the cancer has existed for some time the nodular 
condition becomes more apparent. On section a whitish milklike 
seroalbuminous fluid exudes, which is generally called cancer juice. 
The ill-defined limits of cancer invasion necessitate total extirpation 
of the neoplasm and a generous amount of the adjacent and appar- 
ently unaffected tissue to avoid recurrence of the growth. 
Secondary metastatic deposits in internal organs and tissues are 
sharply circumscribed nodes which stand out in great contrast from 
the affected part. The nodes are generally multiple, have a tendency 
to reach to the periphery, and often become umbilicated in the center. 
This is particularly the case with cancer nodes in the liver, spleen, 
and lungs. In the kidnej^s the nodules may be so numerous and so 
extensive as to convert the entire organ into a shapeless mass which 
has been known to weigh as much as 15 kilograms. 
Clinical observations have shown that metastases may be exten- 
sive or limited. The extensive metastatic invasions are found in 
cases of soft cancer, which always grows rapidly, but in cases of hard 
cancer the metastasizing property is limited in extent and slow to 
start. The lymph vessels are the principal channels for the trans- 
mission of secondary metastatic deposits in cancer, while in sarcoma 
metastasis takes place essentially by the blood vessels. As in sar- 
coma (lymph sarcoma), metastasis may take place by a different 
route, the lymph vessels, so in carcinoma, when the neoplasm occurs 
in the stomach or the intestine the cell proliferation may be so close 
to a blood vessel as to admit some of the epithelial cells into the 
blood current to be carried to other tissues. 
Seats. — The common seats for medullary cancers are the pyloric 
ends of the stomach, the mammary gland, uterus, intestine, liver, 
pancreas, kidneys, lung, ovaries, and testicles. As secondary meta- 
static deposits carcinoma may be found in lymph glands, and when the 
emboli gain entrance into the circulation the cancer may develop 
in any tissue where the emboli become lodged. 
Though the usual way of cancer transmission is by the lymph ves- 
sels, less frequently by the blood vessels, it may very rarely be trans- 
ferred by an eruption on a peritoneal surface. These infections 
result from peritoneal rupture and separation of detached cells in 
cancers of the uterus and of the gall bladder. The lesion results 
