604 EXPERIMENTS DEALING WITH 



venesection before the injection, the sugar concentration of the 

 blood falls strikingly slowly in other words, the diffusion of sugar 

 into the tissue space is extremely slow. He does not attempt to 

 explain this remarkable observation, which is wholly opposed to 

 the results obtained by Leathes, who found that within a few 

 minutes of injecting sugar its osmotic pressure in the blood and 

 lymph was equal. 



Asher makes the following points as showing that the injection 

 of a strong sugar solution acts primarily by increasing tissue 

 activity. Like Cohnheim and Lichtheim, who produced hydrsemic 

 plethora by injecting normal salt solution, Asher finds his injection 

 also causes marked secretion of fluid from the mouth, nose, liver, 

 kidneys, and into the alimentary canal ; that these secretions, like 

 the increased lymph flow, are absent if plethora is prevented by 

 previous venesection ; that the post-mortem lymph flow is accom- 

 panied by a parallel post-mortem salivary secretion, and like the 

 latter must therefore be due primarily to increased tissue activity. 

 He does not explain how sugar causes increased tissue activity, nor 

 why this activity should be prevented by previous venesection, 

 unless we are to ascribe it to the slow rate of diffusion of sugar 

 into the tissue of spaces after venesection. 



A review of the results of Asher' s experiments shows that while 

 he is certainly right in regarding tissue activity as a cause of 

 increased lymph flow, it cannot be looked upon as the sole 

 experimental means by which lymph formation can be increased. 

 For the results of many of the experiments of his predecessors can- 

 not be explained by alterations in physiological tissue activity. On 

 the other hand, the experimental conditions under which most 

 of these results were obtained, are purely artificial, and bear no 

 obvious resemblance to conditions which exist in the normal body. 

 We may therefore conclude in answer to the question, under what 

 physiological conditions in the body is the formation of lymph 

 altered, that only one such condition is known, namely, alterations 

 in tissue metabolism. 



In regard to the way in which tissue activity increases lymph 

 flow, Asher points out that there are two possibilities. The first 

 is that during tissue activity katabolic products are formed which, 

 reaching the tissue fluid, must alter the osmotic pressure of lymph 

 as compared with that of the blood. Starling had already pointed 

 to the same fact in the following terms : " Since the final result of 



