Some aspects of nitrogen and energy metabolism in cancerous subjects: a review.

Neoplasia introduces into the body a new race of cells derived from tissues common to ontogeny but differing biologically, structurally, and chemi cally from their ancestors. The new members of the community of organs and tissues intrude them selves on the nicely balanced economy of the or ganism. Adjustments are necessary. The stresses imposed by the new growth often transcend the power of homeostatic mechanisms to maintain the host's integrity. Many disease processes, neoplastic or other wise, kill by producing anatomic lesions that are incompatible with life. Unrelieved obstruction of a hollow viscus or essential pathway, ulceration with overwhelming sepsis or exsanguinating hemor rhage are lethal regardless of their etiology. A few neopla8ms secrete biologically active substances either identical with or similar to naturally occur ring hormones. The intense pharmacologic re sponses elicited ultimately threaten the existence of the host. Some neoplastic and related diseases kill without producing either of these effects. A primary anatomic lesion has often been eradicated by effective therapy, but discontinuous dissemina tion of tumor cells through the body is found at necropsy. The structural defects produced by the metastases are seldom of sufficient magnitude to threaten life solely for anatomic reasons. Exten sive involvement of the liver, for instance, is