620 SPECIAL PHYSIOLOGY. 



lymphatic fistulse, the result of disease in man, and from artificial open- 

 ings established in the lymphatics of a horse's leg. 



The constituents of the chyle are derived essentially from the di- 

 gested food, but the precise source of the lymph contained in the lym- 

 phatics, and also in the lacteals, during the intervals between digestion, 

 is not perfectly understood. In part, the lymph would seem, from its 

 similarity in composition, to be derived from the nutritive plasma, which 

 permeates all the living tissues. This plasma, itself derived from the 

 liquor sanguinis, consists chiefly of that part of the nutrient fluid 

 poured out through the walls of the capillaries, which is not employed 

 for the nutrition of the tissues. The surplus of nutrient materials, 

 together with sufficient water, is supposed to pass into the lymphatics 

 in the form of lymph, and so to be ultimately returned to the blood. 

 It is also supposed that the tissues, themselves undergoing nutrient 

 changes, yield products which may, in part, be fitted to enter the com- 

 mencing lymphatics ; but these, no doubt, chiefly find their way into 

 the capillaries and minute venules, and thus entering the blood, are 

 subsequently cast off as excretory products. Whatever be its source, 

 the fluid and dissolved constituents of the lymph find their way into 

 the commencing lymphatics, through the delicate coats of these ves- 

 sels, which form closed tubes, having no open mouths, and no direct 

 communication with the capillary or other bloodvessels. It has, how- 

 ever, been recently maintained, that the commencing lymphatics com- 

 municate with, or originate in, lacunar spaces, situated in the areolar 

 tissue which pervades the whole body, and that they commence in fine 

 hollow processes in the ramified nuclear fibre-cells of that tissue, which 

 are also supposed to be hollow. But these views have not been 

 confirmed. 



As the commencing lymphatics are generally most abundant in tis- 

 sues in which the nutritive changes are not very active, and least 

 abundant, or not detected, in organs which undergo very rapid meta- 

 morphosis, it is probable that the waste products of nutrition are 

 chiefly, or, in the case of the nervous centres, entirely, returned into 

 the circulation, through the capillaries and minute veins. It is prob- 

 ably correct to infer that the lymphatics do not remove wasted and 

 excrementitious materials, unfit for the further use of the system, as 

 Hunter formerly supposed, but rather that they take up matters which 

 may be again employed in the blood, for the purposes of nutrition. 

 The fibrin of the lymph, which enables that fluid to form a slight co- 

 agulum, though not in the vessels, as occurs with the blood, and also 

 the lymph-corpuscles, which so closely resemble the white corpuscles 

 of the blood, are present before the lymph has passed the lymphatic 

 glands, but they increase in quantity beyond those glands. The fibrin 

 may be partly derived from that portion of the nutritive plasma effused 

 through the walls of the capillaries, which is absorbed by the com- 

 mencing lymphatics ; its gradual increase in quantity in the larger 

 lymphatics may depend on inspissation, or enrichment, taking place 

 within the glands, which are very vascular; additional fibrin or fibrin- 

 ogen, from which the fibrin is formed, may even be elaborated in these 

 glands. The lymph corpuscles may also be, in some way, more abun- 



