126 



Prof. J. A. MacWilliam. On the [Oct. 24, 



Morgen* heated a ring from the oesophagus of the dog and observed 

 abolition of irritability at about 50°. 



From the evidence available it is clear that relaxation at 50 — 55° C. 

 is a phenomenon of widespread occurrence in living mammalian 

 unstriped muscle showing tonic contraction ; the muscle is dead when 

 this relaxation is completed. 



Experiments on the Amia and Pulmonary Artery. 



Transverse and longitudinal strips were examined soon after death 

 in the same way as the carotid. The changes observed were similar 

 in general character to those described in the carotid at similar periods 

 after death — relaxation about 50 — 55°, preceded in many cases by con- 

 traction, &c. 



But these changes are very slight in extent in the aorta and 

 pulmonary artery, as might be expected in vessels provided with 

 muscular tissue in relatively small amount. (Fig. 8.) 



Fig. 8. 



At the same time the contraction at 60 — 65° is hardly so extensive 

 as might have been looked for in strips containing so much elastic and 

 connective tissue. 



* ' Untereuch. aus d. Physiol. Inst, zu Halle/ vol. 2, p. 161 (1890). 



