3 io PRODUCTION AND ABSORPTION OF L YMPH. 



the serum will tend to become gradually weaker, so that the watery 

 and saline constituents corresponding to the proteid used up can then 

 be absorbed by the blood vessels in the way I have indicated. 



The physical process which I have described above as causing the 

 absorption of lymph by the blood vessels must be in action at all times 

 in the body, and must therefore be a predominant factor in the process of 

 absorption. I have not been able to absolutely exclude the absorption 

 of proteids by the blood vessels, but, in the absence of direct experi- 

 mental evidence that such an absorption does occur, the physical factors 

 I have described in this chapter suffice to explain the phenomena of 

 absorption observed both under normal and under pathological conditions. 



ON THE FUNCTIONS OF THE LYMI% IN THE NUTRITION OF 



THE TISSUES. 



The fact that the tissue cells are bathed by lymph and are 

 separated by this fluid and by the capillary wall from the blood, 

 shows that in all interchanges between blood and tissues the lymph 

 must act as the medium of communication. 



I have already mentioned the irrigation theory of Bartholin, accord- 

 ing to which the nutrition of the tissues was carried out by a taking up 

 of solids from the lymph as it left the blood vessels, so that only pure 

 water (or water and salts Eudbeck) was left over to be carried away 

 by the lymphatics. 



The observations of the Ludwig school on the lymph flow from the 

 limbs, showed clearly, however, that the nutrition of the tissues could 

 be normally carried out without any lymph flow at all. The muscles 

 of a resting limb are taking up nourishment as well as oxygen from the 

 blood, and giving off their waste products, carbonic acid and ammonia, 

 although not a drop of lymph may flow from a cannula placed in a 

 lymphatic trunk of the limb. It is evident, therefore, that to a large 

 extent, at any rate, the giving up of nourishment by blood to tissues and 

 the taking up of the waste products of the latter through the inter- 

 mediation of the lymph, is carried out in the same way as are the gaseous 

 interchanges i.e. by a process of diffusion. 



I have already mentioned the experiments which demonstrate the 

 extreme rapidity with which diffusion takes place between the blood and 

 the lymph, so that, as Leathes points out, the time taken for the 

 equalisation of the constitution of the two fluids after introduction of 

 some diffusible substance into the blood is " inappreciable." There can 

 be no doubt that such changes are of great importance for the normal 

 metabolism of the tissues. Thus there has been considerable discussion 

 of late years concerning the supply of lime to the cells of the mammary 

 gland. Heidenhain pointed out that if the lime were supplied to the cells 

 by filtration, the whole flow from the thoracic duct would be inadequate 

 for the purpose. His conclusion that the lymph with its constituents is 

 therefore a secretion is, however, unnecessary. As the gland cell uses 

 up or turns out lime into the ducts of the gland, it will take up lime 

 from the adjoining lymph, thus lowering the partial osmotic tension of 

 the lime in its neighbourhood. There will be, therefore, a passage of 

 lime from blood to lymph by a process of diffusion, to supply the 

 deficiency. No flow of lymph at all is necessary to furnish the amount 

 of lime required by the gland cell. 



