2 Trans. Acad. Sci. of St. Louis 



diseases. They may lead to the neutralization of the 

 toxin produced as, for instance, in diphtheria, or they may 

 be directed mainly against the invading organism as such, 

 as for instance, in vaccinia, which is a very much miti- 

 gated, quite innocuous variety of smallpox. 



If we compare with this process the changes which take 

 place in cancer, we find a notable difference. In cancer 

 certain constituents of the body and its component tis- 

 sues, namely, the microscopic cells, multiply abnormally 

 and invade the surrounding tissue; they penetrate far- 

 ther and farther. They not only multiply, but very often 

 actually move, migrate and push into the lymph chan- 

 nels and blood vessels. Once this is accomplished they are 

 carried away by the blood or lymph stream to various 

 parts of the body and there set up similar new growths 

 by again multiplying and migrating into the neighboring 

 tissue. These secondary growths are called metastases. 

 They are composed of the same kind of cells which orig- 

 inally began to grow. 



Usually cancer begins as a sharply localized growth 

 and the multiplication and migration of cells is limited to 

 one kind of cells. Any kind of tissue may thus become 

 overactive, cancerous. It may be certain parts of the 

 skin, mammary gland, stomach, tongue, cheek, intestine, 

 liver, uterus. If it starts in the skin, skin-like forma- 

 tions are produced in excess, and in the most varied parts 

 of the body where they do not occur normally. When 

 the cancer starts in the mammary gland, breast tissue 

 grows in excess and is found in internal organs as metas- 

 tases. So it is with the stomach. In cancer of the stom- 

 ach irregular stomach tissue may be found in the stom- 

 ach itself, but a few cells may be carried to the liver and 

 elsewhere and start the growth of stomach tissue there. 

 In the ovary and testes, and occasionally elsewhere, not 

 only single tissue may be found to grow, but through the 

 simultaneous growth of various tissues very complex 



