MISCELLANEOUS: STIMULI UNDERLYING TUMOR-FORMATION 519 



the surrounding tissues to compensate for the substances re- 

 moved by growth as the tumors develop, and especially as they 

 rupture to the surface and are not protected against irregular 

 loss of water. Possibly there may be a third factor involved, 

 viz., excessive turgor, due to the pressure of too much absorbed 

 water. 



That there is an excessive movement of food-stuffs center- 

 ing in all active tumors is shown not only by the rapid growth 

 of such tumors, but also by chemical and microscopic analyses, 

 by the overgrowth of neighboring tissues not actually involved 

 in the tumor itself but affected by it (see Fig. 319, subs. 5 and 6), 

 and, finally, by the starvation of remoter normal tissues. 



What proportion the air dissolved in the circulating fluids 

 of the plant bears to the direct intake of air through the lenticels 

 or the stomata in furnishing oxygen to the cells cannot be stated. 

 It is conceivable that in many cases the first or indirect source 

 would furnish more oxygen to many cells, especially in very 

 young organs, the stomata on which are usually closed and the 

 intercellular passages n which are undeveloped, while in other 

 cases the second or direct source would be most drawn upon. 

 Certainly all the water that enters the transpiring plant through 

 its root-system (in the aggregate, an enormous amount), as w r ell 

 as all the fluid that circulates in animals, is well aerated and 

 bathes all the normal living tissues continuously, but there is 

 not much active circulation in tumors, and consequently their 

 cells will receive less oxygen from this source than normal cells. 



The hyperplasias produced from the flesh of raw potatoes in 

 sealed tubes and those developed under stomata on young shoots 

 in such sealed tubes, I would explain in the same way. As 

 factors in the production of hyperplasias under the stomata, 

 I believe we may eliminate both the decreasing external oxygen 

 and the increasing external carbon dioxid in the sealed tubes, 



Squibb's petrolatum. The cells of the lenticel have multiplied and pushed up 

 the epidermis but have not yet ruptured it. Photographed March 11, 1918, 

 from a water mount of an unstained free-hand section. 16 mm. obj., 4 oc., 

 bellows at 52. For well developed intumescences see Fig. 394*. 



B. Same as A, but passing through a normal lenticel. From a free-hand 

 unstained section in a water mount. The dark color is due to chlorophyll. Photo- 

 graphed March 11, 1918. 16 mm. obj., 4 oc., bellows at 52 (small upright stand). 



