72 CARNEGIE INSTITUTION OF WASHINGTON. 



Since the diaphragm is primarily a respiratory muscle, it would seem 

 possible that the power of absorption of particulate matter from the peritoneal 

 cavity, as actively shown by the lymphatics of the diaphragm, might have a 

 mechanical relation to the act of respiration. In order to test this possibility, 

 Dr. Cunningham has studied absorption in the fetus (cat) before and after 

 respiratory mechanism is developed. His experiments make it evident that 

 absorption through the diaphragmatic lymphatics does not take place to any 

 marked extent in the earlier stages, but increases with age, until at term it is 

 quite appreciable, although even then the absorption is slower than in the 

 newborn and adult. In fetuses under 50 mm. in length, when no respiratory 

 movements can be elicited, no carbon particles reached the anterior medias- 

 tinal nodes. In fetuses between 75 mm. and 90 mm. long, when spasmodic 

 efforts at respiratory movements are first observed, a small amount of granular 

 material had reached the anterior mediastinal nodes after an exposure of one 

 hour. Definite respiratory movements are made by fetuses between 90 mm. 

 long and term, and in these a considerable absorption had taken place at the 

 end of an hour. It is thus obvious that the absorption of particulate matter 

 from the peritoneal cavity via the diaphragmatic lymphatics becomes active 

 at a period at which the fetus begins to make respiratory movements, and 

 after birth, with the beginning of active respiration, there is a decided increase 

 in the amount and rapidity of absorption. The rate of absorption and the 

 muscular activity of the diaphragm are unquestionably associated, and one 

 must suppose that the movements of the diaphragm against the adjacent 

 viscera result in a favorable placing of the granules or adding a necesary 

 movement or pressure to induce their ingestion by the cytoplasm of the serosal 

 lining cells. 



It has been shown by Dr. H. H. Woollard and Dr. G. B. Wislocki that 

 through phagocytosis the hemal nodes are able to remove carbon particles 

 that have been injected into the blood-stream of living sheep. Ordinary 

 l3maph-nodes show only traces of the carbon, although, if one lets the carbon 

 reach them by their afferent lymphatics, they show a greater capacity to 

 store it than do the hemal nodes. These investigators find that in the hemal 

 nodes the carbon is lodged in coarse clumps within the cytoplasm of the large 

 mononuclear cells. These conspicuous cells lie either free within the venous 

 lacunse of the node or in the lymphoid tissue surrounding the lacunae. Less 

 frequently they are found in the blood-sinuses. Very fine granules of carbon 

 may be found in the cytoplasm of the reticular cells that form the meshwork 

 of the blood-spaces. The spleen and liver, however, show a much greater 

 power of removing carbon particles from the blood than do the hemal nodes, 

 and it is interesting to note that the accessory spleens (cat and rabbit) possess 

 the power to phagocytize carbon granules in the same degree as the spleen 

 itself. 



Clinical Importance op an Intact Peritoneal Mesothelium. 



Dr. Cunningham has shown that by the injection of various mild irritants 

 into the peritoneal cavity of the cat (if proper precautions are taken against 

 sepsis and undue injury) it is possible to produce marked morphological changes 

 in the mesothelial membrane without causing any adhesions. Apparently, 

 no matter how much the mesothelial cells proliferate as a result of irritation, 

 if the layer of peritoneal lining cells is complete it is sufficient to prevent the 

 adherence of the two layers of peritoneum and thus prevent adhesions. 



