ABSORPTION FROM THE JOINT CAVITY

¹ Anatomy School, Cambridge

1. Removal of true solutions, colloidal solutions and fine suspensions from the joint cavity into the subsynovial tissues occurs comparatively rapidly. The rate is proportional to the size of the particle under consideration.

2. The mechanism of this removal is obscure. The experiments in this paper suggest a predominantly physical process, although an active rôle for the synovial cells has not been excluded.

The mechanism of further removal of substances from the subsynovial tissues varies with the size of particle.

(a) Small particles, e.g. true solutions, enter both capillaries and lymphatics with ease. Most are removed in the blood-stream.

(b) Small colloidal particles, e.g. Congo red, enter both blood capillaries and lymphatics, but with greater difficulty.

(c) Above a certain critical size, probably in the neighbourhood of the globulin molecule, removal by both these routes ceases, with the exception of small quantities which enter lymphatic vessels but are retained in the regional lymphatic glands.

(d) Still larger particles, e.g. 100 m. µ and over, have no route of egress from the subsynovial tissues.

We wish to express our gratitude to Professor H. A. Harris for his stimulating interest. Our thanks are also due to Mr. N. W. Pirie and Mr. R. Markham for their help and advice, and to Mr. J. A. F. Fozzard and Miss R. Ernest for technical assistance.