108 CARNEGIE INSTITUTION OF WASHINGTON. 



foniied by the transfonnation of mesenchyme cells reacting towards an 

 accumulation of fluid in tissue-spaces by flattening out and forming 

 membranes around the inclosed lakelets. Such "blisters" are held to 

 be the beginning of IjTiiphatic endothelium, vessels being formed by 

 the coalescence of neighl)oring blisters. Clark found, however, that 

 the mesenchjnne cells in the injected tadpole's tail did not show any 

 tendency to flatten out and form membranes around the globules of 

 oil, but they maintained their identity as branched mesenchyme cells, 

 retaining their property of slow progressive movement. The only 

 observable reaction on the part of living cells toward the injected 

 globules was a more or less intense leucocytosis, caused probably by 

 slight grades of mfection. In several instances leucocytes were 

 watched as they moved toward an oil-globule, and were seen to flatten 

 out on its surface and then move away again. It would thus appear 

 that the opinion that mesenchyme cells are stimulated by the mechani- 

 cal pressure of globules of fluid to flatten out and fonn membranes, 

 and that these membranes are the beginnings of the lymphatic endo- 

 thelium, fails to stand the test of experiment and of direct observation 

 on the living animal. 



Doctors Paul G. Shipley and Robert S. Cunningham have studied 

 the role of the omentmn in absorption from the peritoneal cavity. 

 To avoid as completely as possible all causes of error, they adopted the 

 following technique. The omentum was drawn out of the body of the 

 animal through a midline incision and immersed in the fluid to be 

 studied. In a number of cases participation of the lymphatics in the 

 absorption of the material was eliminated by preliminary ligature of 

 the thoracic duct. The difficulty of keeping the anmial under an 

 anesthetic for several hours led the authors to use animals that had 

 been decerebrated; for such an animal will lie motionless and rigid, 

 and at the same time the pulse and respiration and the blood-pressure 

 will remain fairly nonnal. The omentum of animals prepared in the 

 manner described were immersed in true solutions, in pseudo-solutions 

 of high molecular dyestuffs like trypan-blue, in colloidal metals, and in 

 filtered India-ink. After exposure for varying lengths of time, the 

 animals were killed and their tissues examined. The use of a solution 

 of citrated cyanide, isotonic with the blood of the animal, followed by 

 fixation of the tissues with acid formalin, enabled the authors to trace 

 the route of removal of the original fluid, the citrated cyanide being 

 precipitated in the tissues by the acid, forming Prussian blue. The 

 results were most extraordinary and most unexpected: it was shown 

 that the drainage was effected by the blood-vessels. The results were 

 identical, whether the thoracic duct had been ligated or not, and 

 experiments with other substances, namely, trypan-blue or India-ink, 

 led to the same conclusions. Consequently it is probable that the 

 omentum plays an important role in the drainage of the peritoneal 



