THEORIES OF LUDWIG AND HE1DENHAIN. 



295 



containing 18 grms. of dextrose (Fig. 42). In this case the fluid that 

 is dragged by the sugar from the tissues into the blood vessels only 

 just suffices to make up for the previous loss of blood. No hydreemic 

 plethora is produced ; there is no rise of capillary pressure, and there 

 is no increase in lymph flow, although an abnormally large amount 

 of dextrose is present in the circulation. 



The fact that the immediate agent in the production of the increased 

 lymph flow is the hydrae- 

 mic plethora which suc- 

 ceeds the injection, explains 

 the point noticed by Heid- 

 enhain, that the efficacy 

 of these substances is di- 



FIG. 42. To show absence of effect of injecting dextrose 

 after a previous bleeding. The description of the 

 curves in Fig. 41 also applies to this figure. 



rectly proportional to their 



attraction for water ( Was- 



seranziehungsvermogen), i.e. 



to the osmotic pressure of the solution injected, and is therefore a 



function of their molecular weights. A similar relation was noticed 



by von Limbeck 1 to hold for the diuretic action of these bodies, which 



may therefore also be possibly determined directly by the hydrsemic 



plethora. 



The advocates of the secretory hypothesis have laid great stress on 

 the fact that if we analyse the lymph and the blood at different periods 

 after the injection of sugar, we find that the amount of this substance in 

 the blood steadily diminishes (even when the kidneys are cut out of the 

 circulation), while the sugar in the lymph gradually rises to a maximum 

 and then diminishes parallel with but above that in the plasma. This 

 was found to hold good for sugar by Heidenhain, 2 for potassium iodide 

 by Ascher, 3 and for commercial peptone by myself. 4 We are not, how- 

 ever, justified in concluding from these facts that the sugar, etc., have 

 been turned out from the blood vessels against pressure, so to speak. 

 As Cohnstein 5 has pointed out, the lymph flowing at any given moment 

 from the thoracic duct does not represent the transudation from the 

 blood at that moment, but is derived from the lymph that has been 

 formed some time previously. If we had a solution of sugar in gradually 

 diminishing strength flowing into a lymphatic trunk of the leg, it is evident 

 that this fluid would mix with the lymph in the other lymphatics, through 

 which it flowed on its way to the thoracic duct. Later, the solution of 

 sugar would have displaced practically all the lymph from these channels, 

 and would flow through the thoracic duct almost undiluted. It would 

 take, however, some considerable time to flow from the leg to the 

 thoracic duct, so that the outflow from the duct would represent, not the 

 fluid which was being injected into the leg at that moment, but the 

 stronger solution which had been flowing in some time previously. If 

 one compared, therefore, the percentage of sugar in the fluid flowing 

 from the duct and in the fluid flowing into the leg lymphatic at different 

 times after the beginning of the injection, we should obtain a curve 

 exactly similar to those obtained by Heidenhain after the injection of 

 sugar into the circulation, and regarded by him as undeniable evidence 



1 Arch. f. exper. Path. u. Pharmakol., Leipzig, 1888, Bd. xxv. S. 69. 



2 Loc. cit. 3 Ztschr.f. BioL, Miinchen, 1893, Bd. xxix. S. 247. 



4 Starling, Journ. PhysioL, Cambridge and London, 1893, vol. xiv. p. 131. 



5 Arch.f. d. ges. PhysioL, Bonn, Bd. lix. S. 350. 



