The results of ligation of the pulmonary and cutaneous arteries in the frog

The frog possesses, in the lungs and the skin, two organs for the purpose of respiratory exchange, and it has long been established that the skin respiration suffices for his needs at low temperature.

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 exchange 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.