498 CHARACTERS OF LYMPH. [BOOK n. 



lymph (or chyle) a reddish tinge. They have been observed 

 within the living lymphatic vessels, even within small ones, and 

 have probably in some manner or other made their way from the 

 ^blood into the lymph channels. 



296. The chemical composition of lymph, even when taken 

 in each case from the thoracic duct, varies a good deal. The total 

 solids are much less than in blood, amounting in general to not 

 more than 5 or 6 p.c. Hence the venous blood of a vascular area 

 contains rather more solids than the arterial blood of the same 

 area, since the blood in giving rise to the lymph during its passage 

 through the capillaries from the arteries to the veins has parted 

 with relatively more water than solid matter. 



The proteids amount on the average to about 3 or 4 p.c., that 

 is to say, to about half as much as in blood, the particular proteids 

 present being the same as in blood, viz. albumin, paraglobulin and 

 antecedents of fibrin. In lymph, as distinguished from chyle, the 

 quantity of fat is small, and consists of the usual neutral fats and 

 the soaps of their fatty acids, together with lecithin ; cholesterin 

 may also be present. A certain amount of sugar (dextrose) appears 

 to be always present, and several observers have found an appreci- 

 able quantity of urea. The ash of lymph like that of blood serum 

 contains a considerable quantity of sodium chloride, while phos- 

 phates and potash are scanty; it also contains iron, apparently 

 in too great a quantity to be accounted for by the few red 

 corpuscles which may be present. From lymph a certain amount 

 of gas can be extracted, consisting chiefly or almost exclusively of 

 carbonic acid, with a small quantity of nitrogen, the amount of 

 oxygen present being exceedingly small. The importance of this 

 we shall see when we come to study respiration. 



Broadly speaking we may say that all the substances present 

 in blood-plasma are present also in lymph, but are accompanied 

 by a larger quantity of water. 



297. Lymph may also be obtained from separate regions of 

 the body, as from the lower or upper limbs, for instance, by intro- 

 ducing a fine cannula into a lymphatic vessel. In its general 

 features the lymph so obtained resembles that taken from the 

 thoracic duct. Analyses of the lymph distending the subcuta- 

 neous connective tissue in cases of dropsy shew that this contains 

 much less solid matter than normal lymph taken from the thoracic 

 duct or larger lymphatic vessels. From this it has been inferred 

 that the lymph normally existing in the lymph-spaces, lymph- 

 capillaries and minute vessels contains an excess of water ; and 

 indeed it has been asserted that the per-centage of solids 

 increases in passing from the smaller to the larger vessels ; but 

 this cannot be regarded as distinctly proved. The number of cor- 

 puscles however, as we have already said, appears to be increased 

 in passing through the lymphatic glands. It has also been stated 

 that the lymph in the finer lymph- vessels clots even less firmly than 



