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



with those taken from relaxed arteries ; transverse strips exhibit the 

 most notable contrasts. As the condition of post-mortem contraction 

 does not seem to have been taken into account by previous observers 

 or known to them, it was obviously important to test the arterial wall 

 in the conditions of contraction and relaxation respectively. 



Fig. 12. — Aorta (sheep). Transverse strip. Interval of 12 minutes after unloading ; 

 then loaded a second time after the drum had been moved on about 1 cm. 



Fig. 13. — Aorta (sheep). Longitudinal strip. 



Relaxed Arteries. — Both transverse and longitudinal strips made 

 from a relaxed artery show broad features that are similar in the 

 main ; the artery may be relaxed by any of the methods already 

 described. 



The result obtained is similar to what has just been described in the 

 case of the aorta and pulmonary artery. 



Effects of repeated Stretching. — I have made numerous experiments on 

 the effect of again stretching a strip of arterial wall some little time 

 after it has been stretched by the addition of weights in the usual way 

 and then unloaded. 



