FORM AT/OX OF JAM I'll 335 



out, for tile j)rc.sent, any question of activity on the part of the endo- 

 Tlielium) until an osmotic equilibrium is established in the tissues and 

 in the blood. As a matter of fact, however, the blood proteins are not 

 absolutely non-diifusible, but small quantities do pass through the cap- 

 illary walls, and so lymph under such a hypothetical condition would 

 consist of a mixture of the same osmotic concentration as the blood 

 plasma, with about the same proportion of crystalloids, but a smaller 

 proportion of proteins ; this, it will be noticed, is just about the com- 

 position of normal lymph. During life, however, the cells of the tis- 

 sues are causing metabolic changes in these lym])hatic constituents, 

 and these changes consist chiefly in breaking down large molecules of 

 proteins, carbohydrates, and fats into much smaller molecules. Now 

 the osmotic pressure of a solution is dependent upon the numher of 

 molecules and ions it contains, hence by breaking down these few 

 large molecules with verj^ little osmotic pressure into many small mol- 

 ecules, the osmotic pressure in these cells and tissues becomes raised 

 above that of the blood-vessels, and consequently water flows out of 

 the vessels because of the increased pressure. We see here the prob- 

 able explanation of the stimulating influence of metabolic products 

 upon the formation of lymph, noted by Hamburger, Heidenhain, and 

 others. For suggesting and urging the importance of osmotic pres- 

 sure in the formation of lymph we are indebted particularly to Hei- 

 denhain, V. Koranyi,^" J. Loeb,^^ and Roth.^- Loeb show^s very clearly 

 the relative greatness of the water-driving force of osmotic pressure 

 as compared to that of blood-pressure, by his statement that the os- 

 motic pressure of a physiological salt solution is about 4.9 atmospheres, 

 which is twenty ti)nes as great as the hJood jjressure with which we 

 have to do in ordinary physiological experiments. In varying osmotic 

 conditions we may readily see an explanation for the increased lymph 

 flow that occurs during tissue activity ; namely, it is due to the in- 

 creased formation of metabolic products. ]Many of the lymphagogues 

 may act similarly by stimulating metabolic activity, with resulting in- 

 crease in the formation of osmotic pressure-raising products of metab- 

 olism in the organs ; e. g., the increased lymph flow from the thoracic 

 duct that follows stimulation of hepatic activity by injection of pep- 

 tone (Heidenhain) or ammonium tartrate (Asher and Busch).^^ As 

 we shall see later in considering edema, osmotic pressure may play an 

 important part in the pathological formation of lymph. It must be 

 admitted, however, that there are many difficulties in the way of 

 accepting unqualifiedly the original views as to the importance of 

 osmotic pressure in lymph formation. For example, the lymph con- 

 tains more chlorides and may have a much higher osmotic pressure 



loZeit. f. klin. Med.. 1807 (33), 1: 1898 (34), 1. 

 iiPfliicrer's Arch., 1898 (71), 457. 

 12 Englemann's Arch., 1899, p. 416. 

 i3Zeit. f. Biol., 190O (40), 333. 



