Results of Ligation in the Frog. 



83 



lished that the skin respiration suffices for his needs at low tem- 

 perature. 



I have attempted to produce asphyxia in frogs by ligating 

 the vessels which carry blood to the lungs and to the skin. It 

 may be well to mention here certain anatomical data. The 

 truncus arteriosus rises from the heart of the frog and divides 

 into a right and left branch which each give off three branches, 

 the carotid, the aorta and the pulmocutaneous. The last divides 

 into two, one of which goes to the lungs and the other, the cutaneous, 

 supplies the skin of the entire trunk. A large branch from the 

 carotid makes a free anastomosis with the cutaneous artery. 



At temperatures below 20° C. the frog requires very little 

 gas exchange and I found that ligation of the pulmocutaneous and 

 anastomosis was not sufficient to produce asphyxia, although it 

 deprives the frog of the lungs and most of the skin, leaving only 

 the mucous membrane of the mouth and the skin of the legs 

 for respiratory purposes. If in addition the mouth was excluded, 

 by ligation of the carotid arteries, thus leaving only the skin of the 

 legs, the frogs died in 2-3 days. If the lungs and entire skin were 

 excluded by ligating the pulmocutaneous and the iliac arteries 

 death occurred in about 36 hours in spite of the respiratory ex- 

 change through the mucous membrane of the mouth. Frogs in 

 which the respiration of the lungs and mouth was absolutely 

 prevented by keeping them under water, but in which the entire 

 skin was available, lived indefinitely at this temperature. 



With an increase of temperature to 28 0 frogs in which the 

 cutaneous respiration was entirely excluded by ligation of the 

 cutaneous and iliac arteries were still able to live indefinitely. 

 If the lungs and skin of the body were excluded by ligation of the 

 pulmocutaneous and anastomosing arteries, death occurred in 

 about 24 hours, and if the skin of the legs was also excluded by 

 ligation of the iliac arteries, in about 12 hours. If the pulmonary 

 and buccal respiration was prevented by keeping frogs under 

 water, no asphyxia was noted during the five hours of the experi- 

 ment, but frogs in which the cutaneous arteries were tied and 

 which were kept under water died within 3 hours. 



At a temperature of 34°, asphyxia could be caused by excluding 

 the cutaneous respiration. Frogs in which the cutaneous and 



