THE GENERAL CONSTITUTION OF LIVING BEINGS. 85 
to the heterotopy of some other element, that is, to the ap- 
pearance of that element where it is not usually produced. 
Cancer, for instance, that terrible cancer, gnawing and 
spreading, is wholly composed—who would have believed 
it ?—of an excessive development of epithelial cells iden- 
tical with those of our skin, or differing from them only 
by slight peculiarities whose origin is easily explained. 
Phthisis, that terrible scourge which decimates our race, is 
caused by the development of a matter called tuberculous, 
composed of epithelial embryoplastic nuclei, become gran- 
ular and fatty, and mixed with spindle-shaped bodies, all of 
them elements that are formed in the system in the usual 
state. The lungs are thus attacked and destroyed by prod- 
ucts of a cheesy appearance, made by the effect of the 
same law that governs normal products, but under different 
conditions. Heterotopy discloses to us other phenomena 
equally extraordinary. There have been found in the 
ovary cysts containing in their inner wall a true skin, fur- 
nished with papille, epidermis, hairy follicles, hairs, and 
perspiratory glands. Teeth have even been found devel- 
oping in the abdomen. All these organs are accidentally 
produced in those regions, having by fortuitous concourse 
found the circumstances favorable to their appearance all 
existing there. Robin has remarked, in the neighborhood 
of certain glands of the body, the formation of small masses 
consisting wholly of tissue identical with that of the 
breast. So, too, late experiments by Ollier and Goujon, con- 
firming those of Flourens, have taught us that bones may 
be produced at any points in the system to which perios- 
teum or fresh marrow is taken, in the stomach, for instance. 
This singular production of bony substance has not yet 
been observed taking place spontaneously, but it is easy to 
effect it by experiment on animals. 
The formation of the tissue of a scar is nothing else 
than a renovation of the layer-tissue of the skin; and all 
