ORIGIN AND USES OF THE LYMPH. 299 



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in diameter, called sometimes globulins, are almost constantly present in the 

 lymph. These are insoluble in ether and acetic acid but are dissolved by 

 ammonia. They were regarded by Robin as a variety of leucocytes and 

 described by him as free nuclei. 



Origin and Uses of the Lymph. There can hardly be any doubt concern- 

 ing the source of most of the liquid portions of the lymph, for they can bo 

 derived only from the blood. Although the exact relations between the 

 smallest lymphatics and the blood-vessels have not been made out in all parts 

 of the system, there is manifestly no anatomical reason why the water, mixed 

 with albuminoid matters and holding salts in solution, should not pass from 

 the blood into the lymphatics ; and this is rendered nearly certain by the fact 

 that the lymphatics surround many of the blood-vessels. In comparing the 

 composition of the lymph with that of the plasma of the blood, it is seen that 

 the constituents of these fluids are nearly if not quite identical ; the only 

 variations being in their relative proportions. This is another argument in 

 favor of the passage of most of the constituents of the blood into the lymph. 



One of the most important physiological facts in the chemical history of 

 the lymph is the constant existence of a considerable proportion of urea. 

 This can not be derived from the blood, for its proportion is greater in the 

 lymph, notwithstanding the fact that this fluid is being constantly discharged 

 into the blood-vessels. The urea which exists in the lymph is derived from 

 the tissues ; it is discharged then into the blood, and is constantly being 

 removed from this fluid by the kidneys. 



The positive facts upon which to base any precise ideas with regard to the 

 general office of the lymph are not very many. From the composition of 

 this fluid, its mode of circulation, and the fact that it is being constantly dis- 

 charged into the blood, it would not seem to have an important use in the 

 active processes of nutrition. The experiments of Collard de Martigny sus- 

 tain this view, inasmuch as the quantity and the proportion of solid constitu- 

 ents of the lymph were rather increased than diminished in animals that had 

 been deprived of food and drink for several days ; while it is well known that 

 starvation always impoverishes the blood from the first. On the other hand, 

 urea, one of the most important of the products of disassimilation, is undoubt- 

 edly taken up by the lymph and conveyed in this fluid to the blood. It 

 remains for future investigations to determine whether other excrementitious 

 matters may not be taken up from the tissues in the same way a question 

 of importance in its relations to the mechanism of excretion. 



What is positively known with regard to the uses of the lymph may be 

 summed up in a very few words : A great part of its constituents is evidently 

 derived from the blood, and the relations of these to nutrition are not under- 

 stood. The same may be said of sugar, which is a constant constituent of 

 the lymph. Urea and perhaps other excrementitious matters are taken up 

 from the tissues by the lymph, and are discharged into the blood, to be re- 

 moved from the system by the appropriate organs. 



Properties and Composition of Chyle. During the intervals of digestion, 

 the intestinal lymphatics and the thoracic duct carry ordinary lymph ; but 



