14 



ZOOLOGY. 



liquid within the membranous sac in the one case, and 

 within the ;ininial hodv in tin- ntlnT. Jlenee the elevation of 

 tin- LTUin-watcr in the tube, and tin- inen-asi- <>f weight in the 

 living animal, both being due to one cause, namely, endos- 

 mose. 



31. Organi/.nl bodies arc represented 

 by the sac as seen in Fig. 1. They are 

 placed in a surrounding medium more fluid 

 than that existing in their interior. Hence 

 they absorb.* 



32. Organs of Absorption In cer- 

 tain animals low in the scale of life, 

 absorption consists merely in the process 

 we have just described. In these animals 

 there exists no regular circulation in the 

 interior of their bodies ; but in the higher 

 classes of animals the function is more com- 

 plex. The fluids imbibed, as described 

 above, pass into the interior of the \ 

 and there mingle with the nourishing fluids 

 of the animal, and thus mingled and united 

 they pass with the blood to certain parts of 

 the economy, wherever, indeed, that pene- 

 trates. Thus the function of absorption be- 

 comes divided as it* were into two acts; the 

 first, simply the act of imbibition through 

 the tissues ; the second, that of circulation 

 through the interior of the animal. 



33. In all animals the principal agent for this trans- 

 portation of the matters absorbed, to various parts of tin- 

 body, is the blood, acted on by the heart, to which the 

 liquids are conveyed by the veins ; and thus it happens that 

 in the great majority of cases these vessels play an important 

 part in the function of absorption. 



34. In many animals there exist only sanguiferou- 

 seN, and the function is performed by them alone. In others 

 however, and especially the more highly organized, there 



* The paseage of liquids through various membranous coverings is a 

 complex subject, si ill open to inquiry. Thus, if spirits of turpentine be 

 enclosed in a glass jar, as in the setting up <>l' anatomical preparations in 

 the usual way, by means of several layers of bladder, tin-toil, \c., it will in 

 time escape," and, covering the exterior of the glass, obscure the objrrt 

 within. If, on the other hand, only a single layer of bladder be used, none 

 of the turpentine will escape. This curious fact was accidentally discovered 

 by my brother. K. K. 



Fig. 1. 



