2 86 PROD UCTION AND ABSORPTION OF L YMPH. 



forming a colourless clot of fibrin. It contains from 2 to 8 parts 

 per 100 of solids, of which about 1 per cent, consists of inorganic 

 salts, while the rest is made up chiefly of proteids. The proteids are 

 similar to those of the blood plasma ; and it seems that the process of 

 clotting is identical in the two fluids. The salts vary very little in 

 different samples of lymph, and are generally described as being present 

 in exactly the same proportions as in the blood plasma from which the 

 analysed specimen of lymph was derived. Hamburger has recently 

 called attention to the existence of minute differences of composition in 

 the salts of the two fluids, and this difference may be credibly ascribed 

 to chemical changes effected in the lymph by the tissues over which it 

 has flowed. All specimens of lymph contain leucocytes, chiefly of the 

 small uninuclear variety ; these are foun4 in greater numbers after the 

 lymph has passed through a lymphatic gland. Further information re- 

 garding the composition of lymph will be found in the article on lymph 

 and serous exudations (p. 181). 



The similarity in composition between liquor sanguinis and lymph 

 suggests that the latter may be regarded as part of the plasma which 

 exudes through the capillary wall, bathes all the tissue elements, and is 

 collected by the lymphatics into the thoracic duct to be returned again 

 to the blood. 



Forces involved in lymph production. Older theories. As to 

 the forces involved in its production and the use of this fluid in the 

 functions of the body, the most various views have been held. Asellius, 1 

 who discovered the lacteals in 1622, thought that these ducts 

 carried the foodstuffs from the intestines to the liver to be there 

 elaborated into blood. In order to explain the filling of the lacteals 

 from the intestines, Asellius invoked the aid of the complicated 

 mechanism which had already been imagined by Avicenna to account 

 for the filling of the mesenteric veins. He explained the passage of 

 chyle to the liver as due partly to the intestinal movements and partly 

 to the suction-action of the blood vessels and of the liver itself. The 

 chief factor however was, according to him, the suction-action exerted 

 by the open mouths of the lacteals themselves, and he compares the 

 latter to leeches, which suck blood from any surface to which they are 

 applied. This theory was overthrown by Pecquet 2 by the discovery of 

 the connection of the lacteals with the thoracic duct and through this 

 with the venous system. The general lymphatics were discovered 

 by Eudbeck 3 and Bartholin 4 almost simultaneously. In these authors 

 we meet with the first conception of lymph apart from absorbed 

 foodstuffs ; moreover, Bartholin, assuming that this lymph is formed 

 from the blood, discusses the possible ways by which the fluid could 

 get from blood vessels to lymphatics. He thinks it possible that 

 there may be a direct communication between lymphatics and blood 

 vessels, but is more inclined to the view that the communication is 

 indirect by means of the parenchyma of the organs. Failing to remark 

 what Rudbeck had already noticed, namely, that the lymph had a salt 

 taste, and like blood clotted spontaneously, he describes the lymph as 

 pure water, and imagines that from the blood vessels there is a 



1 " De lactibus sive lacteis venis," Basel, 1628. 



2 "Experimenta nova anatomica," Paris, 1654. 



3 "Nova exercitatio anatomica, etc." 1653. 



4 " Vasa lymph atica nuper in animantibus inventa," Hafniae, 1653. 



