360 SYSTEM OF LACTEAL AND LYMPHATIC VESSELS. 



Whether thin soap-solutions are advisable, however, has not as yet been deter- 

 mined. This mode of administering nutriment by means of nutrient enemata, 

 must, however, always remain imperfect; at best only one-quarter of the amount 

 of proteids necessary for the maintenance of the metabolic equilibrium is absorbed. 



SYSTEM OF LACTEAL AND LYMPHATIC VESSELS. 



Within the tissues of the body, and even in those without special 

 blood-vessels (cornea) or with but a poor supply, there is present a 

 system of vessels conveying fluid, and within which the movement is only 

 centripetal. These vessels begin within the parenchyma of the organs 

 in widely different ways, and unite in their course to form delicate, 

 then thicker tubes, which empty into two trunks of considerable size 

 at the junction of the common jugular and subclavian veins: the tho- 

 racic duct on the left side, the lymphatic trunk on the right. 



The importance of the lymph and of its movement in the various 

 organs is apparent in different ways at different points, (i) In some 

 tissues the lymphatics represent the nutrient channels through which 

 the nutrient fluid given off by adjacent blood-vessels is distributed, as 

 in the cornea particularly and often within the connective tissues. 

 (2) In some tissues, as in the glands, for example the salivary glands 

 and the testicles, the lymph-spaces constitute the chief reservoirs for 

 fluid, from which, at the time of secretion, the cellular elements derive 

 their necessary fluid. (3) In addition, the lymphatic vessels everywhere 

 have the task of collecting the fluid with which the tissues are saturated 

 and of conveying it back again to the blood. If the network of capillary 

 blood-vessels be regarded, from this standpoint, as an irrigation-system, 

 which supplies the tissues with nutrient fluid, the lymphatic system can 

 be considered as a drainage-mechanism, which, in turn, conducts away 

 the excess of the transuded fluids. Metabolic products from the tissues, 

 the products of retrogressive metamorphosis, are added to this return- 

 current. The lymph-channels are thus, at the same time, absorbent 

 vessels: substances that would otherwise be carried to the parenchyma 

 of the tissues are thus also absorbed by the lymphatic system. 



A consideration of these circumstances shows that the system of the 

 lymph-channels represents in reality an appendix to the blood- vascular 

 system ; therefore, further, the lymphatic system cannot be active at all 

 if the circulation of blood is totally interrupted; it operates only as a 

 part of the whole and with the whole. 



If the lacteals are contrasted with the true lymph- vessels, this is 

 done chiefly for anatomical reasons, because the important and con- 

 siderable paths of the former, which are derived from the entire intes- 

 tinal tract, have especially attracted the attention of investigators since 

 antiquity and are to a certain extent an almost independent division 

 of the lymphatic system, with conspicuous absorptive activity. In addi- 

 tion their contents, of white color from the generous admixture of fat- 

 granules, as chyle or lacteal fluid, appeared at first sight to be essen- 

 tially distinct from the clear and watery fluid of the true lymphatics. 

 From the physiological standpoint, however, the lacteals cannot be given 

 an independent position. They are, functionally and structurally, lym- 

 phatics, and their contents are true lymph, mixed with a large amount 

 of absorbed materials. 



