■ 



82 Scientific Proceedings (48). 



capable of standardization against maximal and minimal valves, 1 

 it has been possible to fill this gap in the physiology of the 

 circulation. The operative technic was so adapted that (1) 

 normal intrathoracic pressure relations during inspiration and 

 expiration were obtained when the records were taken, (2) arti- 

 ficial pressure changes in the intrathoracic cannula and manom- 

 eter tubes were obviated, (3) clot formation was minimized and 

 recognized when present, (4) only a small portion of the pul- 

 monary circuit was occluded, and (5) the systemic and right 

 auricle pressures corresponded to that habitually found in animals. 



The results of 13 such experiments showed that, during 

 quiet normal breathing the systolic and diastolic pressures fell 

 during inspiration and rose during expiration. The systolic 

 pressure averaged 43.3 mm. in expiration and 31.7 mm. in 

 inspiration, the diastolic pressure 20 mm. in inspiration and 

 1 1.9 mm. in expiration. In experiments where the heart rate 

 ranged from 180 to 25 per minute, it was found that the diastolic 

 pressure decreases as the heart rate is reduced. The same holds 

 true for the systolic pressure between heart rates ranging from 

 from 180 to 100 or 80 (the latter figure varying in different ani- 

 mals). When the heart becomes still slower the systolic pressure 

 again increases. 



During temporary apnea vagi, the maximal pressure dropped 

 40 to 32 per cent., the minimal pressure increased 10-25 P er cent, 

 over that occurring during natural breathing, showing that respi- 

 ratory movements determine to a pronounced extent the ex- 

 treme pressures in the pulmonary artery. 



61 (670) 



The results of ligation of the pulmonary and cutaneous arteries 



in the frog. 



By T. S. GlTHENS. 



[From the Department of Physiology and Pharmacology of the 

 Rockefeller Institute for Medical Research.] 



The frog possesses, in the lungs and the skin, two organs for 

 the purpose of respiratory exchange, and it has long been estab- 



1 Wiggers, Journ. Exp. Med., XV, 1912, p. 174. 



