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Prof. W. M. Bayliss. 



•experiment, 50 c.c. of urine were found in the bladder, while 30 c.c. had been 

 passed in the course of the experiment. 



Other experiments were made with the insertion of a cannula in the bladder; 

 and records made by means of an electrical drop recorder. It was found 

 that while saline solutions produced diuresis, this was not the case with 

 gelatin. For example, only 14 c.c. were excreted in 68 minutes, against 

 2 - 5 c.c. in six minutes ( = 14 c.c. in 34 minutes) before the bleeding. 



The loss of the injected fluid by renal excretion does not, however, explain 

 the phenomenon of the fall of blood pressure. It was sometimes found in 

 my experiments that very little urine was produced after the saline injection. 

 This was probably due to the kidney having suffered from want of oxygen 

 ■during the period of low blood pressure following the removal of blood. In 

 fact, it was noticed in one case that a slow renal secretion subsequent to a 

 saline injection was considerably increased by a more vigorous artificial respira- 

 tion, although there had been no signs of asphyxial stimulation of the nerve 

 centres. It is well known that the kidney is sensitive to deficient supply of 

 oxygen. But what concerns us for the present purpose is the fact that, 

 although there may be no increased loss of fluid by renal excretion, yet the 

 .arterial pressure falls rapidly after saline injections. 



The additional factor is, no doubt, passage of fluid into the tissues. Bogert, 

 Underhill and Mendel (17) have shown that saline solutions pass into the 

 tissues rapidly and that the kidney is not necessary for the removal of excess 

 of fluid from the circulation after intravenous injections into the normal 

 animal. Moreover, the production of oedema by perfusion with Ringer's 

 solution is familiar to all who have made such experiments. The liver, in 

 particular, swells to a great extent when saline solutions are injected. This 

 is obvious to the eye, and in some plethysmographic experiments on a lobe of 

 the liver which I made some years ago, I noticed a very considerable increase 

 in volume under such circumstances. In the experiments to be referred to 

 below, in which a limb was perfused with Binger's solution containing 7 per 

 cent, of gum acacia, the absence of oedema was noticeable. We have also 

 seen above that the blood pressure remains high for a long time after the 

 injection of gum or gelatin, but falls after starch solutions. In what way, 

 then, do gum and gelatin differ from starch 1 Clearly in the possession of 

 osmotic pressure. Starling (7) has emphasized the importance of the osmotic 

 pressures of the protein content of blood and tissue fluids in the passage of 

 water from one to the other. The protein content of the blood plasma is 

 higher than that of the tissue lymph, so that there is a continual attraction 

 of water from' the tissues to the blood. This is, however, normally balanced 

 by filtration in the other direction, which occurs where the pressure in the 



