120 



THE VASCULAR SYSTEM 



arteries both give results wholly different to those of Roy. 

 Mac William finds that there is a great tendency to elongation, 

 in the case of relaxed arteries, when submitted to even low or 



moderate internal pressures. 

 Prolonged and frequently 

 I i recurring periods of relaxa- 



I I tion tend, he says, to pro- 

 duce tortuous arteries ; 



o td 40 MsoiooieQHOiGQiBoaoozzoaM hence the tortuosity of the 



FIG. 12. Carotid (ox), weak contraction anastomotic arteries which 



(5 days p.m.). Increase of capacity. dilate after the ligation of 



a main trunk, and of the arteries of the uterus and mammae 

 which develop so in size during pregnancy, and the extensive 

 pulsation of arteries in inflamed parts. The pulsatile expansion 

 of a contracted artery is very small at any pressure, and there 

 is no evident difference in its amount at different pressures. 

 Hence the assertion of the surgeon 

 is explained, that there is no evi- 

 dence of the transverse expansion 

 of an artery when exposed and 



I I I I I 



*>>> eo 100 eo HO w too no 



measured with callipers (Lister). 



On the other hand, the pulsatile hag 



expansion of a relaxed artery for several days. Length (between 

 f i L ri TT ligatures) 14 mm. Increase of capacity. 



for a given pulse at mm. Hg, 



50 mm. Hg, and 100 mm. Hg is in the proportion 3:2:1. The 

 measurements taken by Roy and others, which show the 

 extensibility of arteries to be increased in pathological states, 

 such as marasmus and phosphorus poisoning, in the light of 

 MacWilliam's work, must be interpreted by showing that the 



"1 I 



T-r-T-nr-r-l I i T1 



HO 40 60 80 100 ISO W 160 100 100 20 SM 160 200 300 XO 340 360 300.400 4SO 

 FIG. 14. Second elevation of pressure in same portion of artery as in Fig. 12. 



muscular rather than the elastic elements are at fault, and 

 that the power of post-mortem contraction is lacking. The 

 extreme degree of contraction produced by exposure and manipu- 



