ANALYSIS OF LYMPH 151 



organs slowly, and that ingredients peculiar to the necessities of the func- 

 tion and growth of the differentiated tissue of the organ are taken from the 

 lymph in special organs. Lymph obtained from a human lymphatic fistula 

 has been analyzed; the figures from Hammarsten are as follows, though 

 considerable variations appear in the analyses from other authorities: 



ANALYSIS OF LYMPH. 



Per cent. 



Water 94 . 5 to 96 . 5 



Solids 3.7 to 5.5 



Proteins 3.4 to 4.1 



Ethereal extract o . 06 to 0.13 



Sugar o.i 



Salts 0.8 to 0.9 



Sodium chloride o. 55 to o. 58 



Sodium carbonate o . 24 



Disodic phosphate 0.028 



The most notable fact to be derived from this composition table is the 

 low percentage of proteins present in the lymph. 



The Formation of Lymph. The manner in which the substances in 

 the lymph pass through the walls of the capillaries from the plasma is a 

 question which has been surrounded with considerable difficulty. It was 

 thought by Ludwig and many of his followers that the process involved 

 is merely one of filtration. Certainly the blood pressure in the capillaries 

 is in the main greater than that of the pressure of the lymph in the surround- 

 ing tissues, and this positive pressure will contribute so much to the direct 

 ingredients of the blood plasma through the capillary walls. It is true, as a 

 matter of experiment, that anything which contributes to an increase in 

 the capillary pressure is very apt to produce an edema of the corresponding 

 tissues. Since the colloidal materials represented by the protein are non- 

 diffusible, one would by this theory expect to find a diminished percentage 

 in the lymph, which is true, though not to the extent which the theory 

 demands. 



Heidenhain was the first to question the adequacy of the blood pres- 

 sure and filtration hypothesis. He showed that many of the conditions 

 under which lymph formation takes place are not sufficient to produce nitra- 

 tions of the material found. He advanced the hypothesis that the living 

 endothelial lining of the blood vessels exerted a secretory activity in lymph 

 production. He discovered that various substances known as lymphagogues 

 when introduced into the circulatory system produce a remarkable increase 

 in the flow of lymph from the thoracic duct. Further, he noticed that the 

 concentration of the lymph was changed; i.e., increased. Heidenhain 

 thought that the lymphagogues acted directly on the capillary and endothelial 



