1034 ABSORPTION 



This is also true of blood-serum and isotonic salt solutions when intro- 

 duced into these spaces. 



In general, it may be said that the endothelium acts in the same man- 

 ner as other animal membranes. Thus, it has been shown by Roth^ 

 that the introduction of hypotonic salt solutions into the peritoneal 

 cavity leads to a rapid absorption of its water until it has become isos- 

 motic with the blood. Eventually, all of the solution disappears from 

 this cavity. A hypertonic salt solution, on the other hand, first draws 

 water from the blood until an isosmotic condition has been established. 

 The fluid as a whole then begins to pass over into the system. It is 

 difficult to explain these phenomena unless we assume with Reckling- 

 hausen^ that the peritoneal cavity stands in direct communication 

 with the lymphatic system by means of minute defects or stomata 

 which are situated between the individual endothelial plates. Thus, 

 while the ordinary laws of diffusion would play the most important 

 part to begin with, the final escape of the fluid would occur through 

 these openings. This explanation has much in its favor and especi- 

 ally since this absorption is proportional to the pressure under which 

 the fluid is injected into the cavity. But inasmuch as the aforesaid 

 stomata have not been definitely recognized by histologists. Starling^ 

 has supposed that the absorption from these cavities is dependent upon 

 the fact that the proteins of the blood are indiffusible and exert, there- 

 fore, a considerable osmotic pressure upon the neighboring salt solu- 

 tion. This explanation is strengthened by the fact that the absorbed 

 material enters the blood and not the lymph, because the ligation 

 of the thoracic duct does not impede this process. Obviously, this 

 subject is still in a decidedly theoretical state and we cannot do much 

 else at the present time than to consider it in the same light as the for- 

 mation of the lymph, ^.e., we must suppose, and rightly so, that the 

 purely physical factors of diffusion and osmosis are modified by the 

 metabolic activity of the endothelial cells. 



Absorption Through the Skin. — It has been stated in one of the 

 preceding chapters that the skin excretes carbon dioxid, water, salts 

 and at times also urea.^ To what extent the skin may also be regarded 

 as an organ of absorption has not been definitely ascertained, although 

 it may be assumed that this function must differ in different animals. 

 Concerning the skin of man it has been established that it possesses 

 practically no absorbing power under ordinary conditions, whereas 

 that of the frogs and eels (not the fish) absorbs oxygen as well as water, 

 alcohol, and possibly also salts and other substances.^ 



1 Engelmann's Archiv., 1899. 



2 Virchow's Archiv, xxvi, 72; also: Meltzer, Jour, of Physiol., xxii, 1898, 196. 



3 Jour, of Physiol., xviii, 1895, 106. 



4 Schierbeck, Archiv fiir Physiol., 1893, and Taylor, Jour. Biol. Chem., ix, 1911, 

 21. 



5 Berg, Dissertation, Dorpat, 1868, Bohr. Skand. Archiv fiir Physiol., x, 1900, 

 88, and Maxwell, Am. Jour, of Physiol., xxxii, 1913, 286. 



