Observations with the electron microscope on the absorption of India ink from the peritoneal cavity of the rabbit.

It has been well known that inert foreign materials, introduced into the peritoneal cavity, are easily and rapidly absorbed by the lymphatic vessel on the surface of the diaphragm as cited briefly in Lymphatics, Lymph and Lymphoid Tissue by Y o f f e y and C o u r t i c e (1956) or in Physiologie und Pathologie des Lymphkreislaufes by R u s z u y a k, F o l d i and S z a b ô (1957). The pinocytotic activity of the peritoneal cells of the rat's diaphragm, observed with the electron microscope by Odor (1956), explains one of the most important mechanisms of absorption from the peritoneal cavity. However, many problems as yet remain. In order to study the absorption from the peritoneal cavity into the lym-' phatics, the site of most intensive absorption where the lymphatic capillaries distribute beneath the peritoneum must be used for the observations. In the rabbit, the lymphatic absorption from the -peritoneal cavity takes place almost wholly at the tendon parts of the diaphragm. The lymphatic capillaries run parallel with one another between the parallel lying tendon bundles, although they are abundantly connected by the oblique or transverse rnnning, anastomosing lymphatics. The findings using the light microscope by k i h a r a (1956) and his scholars have shown that the peritoneal cells covering the area where the lymphatic capillaries distribute are remarkably smaller in size than the common cells. Moreover, the collagenous bundles in the submesothelial layer are loosely arranged beneath the smaller peritoneal cells, although they are compact in the area where the lymphatics do not distribute, and the intraper-