lOi j\Ir Carpenter o?i Unity of Function 



facility, it is evident, that the aliment taken into the stomach 

 bears no different relation with the organism in general, than 

 when applied to the exterior surface of the body. These views 

 may appear trite and almost self apparent, but physiologists 

 are in the habit of overlooking them. 



Pursuing the development of the absorbing system in ani- 

 mals, and the gradual specialization of the function, we find, 

 that, in the higher classes, the process no longer takes place 

 by the general circulating system (as by the mesenteric veins 

 in the Echinoderma), but that a new set of vessels is interposed 

 which is still more peculiarly adapted for the purpose. It 

 would seem that the earliest true lacteal vessels are found in 

 fishes ; and they possess many communications with the venous 

 system, both in this class and in the reptiles. Nearly the same 

 may be said of .the lymphatic vessels whose office it is to per- 

 form interstitial absorption throughout the system. In the Mam- 

 malia, however, the absorbent system is still more specialized by 

 the want of all communication Avith the veins, except through 

 their terminal trunks. By thus tracing the gradual evolution 

 of the special absorbent system from its more general type in 

 the lower classes of animals, we arrive at a knowledge of its 

 veal nature. 



Let us now study this function in another point of view, by 

 applying to it the second general principle with which we set 

 out. Although the roots of plants are evidently their special 

 organs of absorption, there can be no doubt that the leaves and 

 other succulent parts of the general surface perform this func- 

 tion Avhen the former are absent, or afford a deficient supply of 

 nutriment. In many of the epiphytal parasites, the latter are 

 evidently only absorbing organs ; and no one can have observed 

 the effects of atmospheric or artificial moisture on a desiccated 

 plant, without perceiving their importance. That the special 

 function of the leaves is of a totally opposite nature, admits of 

 no doubt ; and we have here, therefore, a most interesting ex- 

 ample of the principle, that the general surface, even in the 

 most highly elaborated organism, retains more or less its pri- 

 mitive community of function. Nay, in the plant, the leaves 

 possess a peculiar power of adapting themselves to the discharge 

 of this office ; for not only do they present a broad expanse of 



