THEORIES OF LUDWIG AND HE1DENHAIN. 
295 
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20 
//y. T 8 grams dextrose 
Fig. 42. — To show absence of effect of injecting dextrose 
after a previous bleeding. The description of the 
curves in Fig. -11 also applies to this figure. 
containing 18 gnus, of dextrose (Fig. 42). In this case the fluid that 
is dragged by the sugar from the tissues into the blood vessels mil)' 
jusi suffices to make up for the previous Loss of blood. No hydraemic 
plethora is produced ; then' is no rise of capillary pressure, and there 
is no increase in lymph How, 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- 
rectly proportional to their 
attraction for water ( Was- 
seraTiaiehiingsvermdgt n >. 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 * to hold for the diuretic action of these bodies, which 
may therefore also he possibly determined directly by the hydraemic 
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 Hewing 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 winch 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, 18S8, Bd. xxv. S. 69. 
2 Zo'\ 3 Ztschr.f. Biol., Mtinchen, 1893, Bd. xxix. S. 247. 
4 Starling, Journ. Physiol., Cambridge and London, 1893, vol. xiv. p. 131. 
5 Arr/i. /. d. ges. Physiol., Bonn, Bd. lix. S. 350. 
