BEHAVIOR OF ANURA TOWARD COLLOIDAL DYES 39 



intestinal fluids, dye might be taken up solely by the intestinal 

 lymphatics and be conveyed to the venous circulation by the 

 usual route. In which case the kidneys might even then be the 

 first to store the dye. As dye solutions actually do pass through 

 the intestinal mucosa, some dye probably reaches the venous 

 circulation by this route. The circumstance that the liver is the 

 first to receive and store the dye when absorption is restricted 

 to the intestinal mucosa, and continues to store it in excess of that 

 stored by the kidneys must, however, be explained in another 

 manner. 



Experiments thus far indicate that dye solutions of relatively 

 low concentration do not pass through the intestinal mucosa of 

 the adult. At least they do not appear to act on typical tissues 

 like solutions of high concentration (Exp. 15, table 9). It is 

 therefore highly probable in the case of solutions of high con- 

 centration, that the dye is absorbed not only by the mucosa and 

 submucosa, but is taken up by the radicles of the portal vein as 

 well. In this manner the dye would be able to reach the liver by 

 a direct route where' it becomes stored by the stellate cells which 

 line the liver capillaries before reaching any other portion of the 

 body. 



Experiments in which the portal of entry is restricted to the 

 integument show, in larval and adult frogs and toads, that the 

 tissues react toward the dye in a uniform and progressive manner, 

 both in relation to the amount of dye which enters the body, and 

 to the length of time the animals are suspended in dye solutions. 

 On the other hand, considerable variation was observed among 

 different individuals in the ability of the intestinal mucosa to 

 absorb the dye. 



Feeding experiments on very young larvae have thus far 

 proved impracticable. I am therefore unable to state in such 

 cases to what extent, if any, the intestinal mucosa may absorb 

 the dye. I am inclined to believe that the bluish appearance 

 presented by the larvae in some cases, may be due to this cause. 

 A few instances have been mentioned in the preceding experi- 

 ments in which its absorption by the mucosa in some of the larvae 

 may have possibly occurred. 



