COMPOSITION AND PROPERTIES OF CHYLE AND LYMPH. 217 



fluid for the purpose of being ultimately discharged by the excretory organs. 

 But the main agent iu the process appears to be the constant and considera- 

 ble pressure exerted by the blood against the inner surface of the vessels, 

 effecting a filtration of its fluid portions into the irregular cavities and in- 

 terspaces of the connective tissue which are now believed to constitute the 

 true origin of the Lymphatics. This view receives support from the experi- 

 ments of Tomsa, 1 who has shown that the injection of serum into the vessels 

 immediately after death, at the ordinary pressure of the blood, is followed 

 by the filtration of a fluid closely analogous to lymph iu its characters, which 

 can readily be obtained from the lymphatic vessels. And there is abun- 

 dant evidence to show that those circumstances which tend to increase the 

 pressure in the capillaries, either by forcing more blood into the part, 2 or by 

 preventing its return by ligature or pressure applied to the veins (provided 

 that complete stoppage of the current of the blood is not produced), are fol- 

 lowed by an increased discharge of lymph, as well as of lymph-corpuscles, 3 

 from the larger absorbent vessels. It is easily intelligible that various other 

 causes besides pressure may influence the quantity and quality of this fluid, 

 which, as Milne-Edwards 4 observes, is poured forth to irrigate the various 

 organs of the body ; for besides the important condition of the quality of the 

 blood (with the effects of variations in which we are but imperfectly ac- 

 quainted ), differences in the thickness of the walls of the vessels and of the 

 external pressure to which they are subjected, may to some extent be the 

 causes of those differences in the nature of the transudate observed iu Hy- 

 drocephalus, Ascites, and Hydrocele. D That the central nervous system exer- 

 cises considerable influence over the process of absorption is clearly shown 

 by the experiments of Goltz. 6 In these, which were made upon frogs, ren- 

 dered motionless by woorara, the brain and spinal cord were removed in 

 some instances, whilst in others they were left intact. In both sets of frogs 

 fluid was injected into the dorsal lymph-sac, and it was found that the fluid 

 was rapidly carried off in those in which the brain and spinal cord were un- 

 injured, whilst little or no absorption took place in those iu which those 

 organs had been removed. Nasse, 7 who has also investigated this subject, 

 found that irritation of sensory nerves caused increase iu the flow of lymph. 

 Excitation of the pneumogastric trunk, or of its centric extremity when di- 



1 The serum used in Tomsa's experiments contained from 6 77 to 6. '26 per cent, of 

 solid residue, and that obtained from the Lymphatics from 6.12 to 4.36 per cent , 

 which is about the proportion in ordinary lymph. Paschutin, however, has arrivnl 

 at a different conclusion, and believes that variations in the arterial pressure have no 

 influence on the flow of lymph. The secretion is increased, and its composition altered 

 by the administration of woorara. His experiments were made on the lymphatics of 

 the fore leg of the dog. Sitz. d. Konig, Sachs. Gesellsch. d. Wiss., 1873, p. 95. For 

 corroborative observations see Genersich in idem, 1870, and Emmmghaus, Ludwig's 

 Arbeiten, 18 7 3, B. viii, p. 51. 



2 As was effected by Mr. Eobinson in his experiment recorded in the Med.-Chir. 

 Trans., vol. xxvi, p. 51, when the aorta just above its division into the common iliacs, 

 and also one of the renal arteries, were tied, and albumen immediately made its ap- 

 pearance in the urine, being as it were forced, by the increased pressure in the remain- 

 ing renal artery, through the delicate filter formed by the walls of the vessels in the 

 Malpighian tufts. 



3 See Cohnheim, Virchow's Archiv, 1867, Bd. xl, p. 1. 



4 See his excellent chapter on Transudation in the Legons sur la Physiologie, vol. 

 iv, 1859, pp. 391-446. 



5 See Hales's liieinastatics, pp. 118-119. 



6 Pfliiger's Archiv, Band v, p. 53. See also Bernstein, Berliner klin. Wochens., 

 1872, No. 28, and E. Heubel Virchow's Archiv, 1872, Bd. Ivi, p. 248. 



7 Centralblatt, 1873, p. 155. 



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