1901.] Properties of the Arterial and Venous Walls. 141 



Marey,* working with the aorta of man and different animals, and 

 using a water-plethysmograph, found that the expansion (resembling the 

 extension of strips of the vascular wall which Wertheimf had first 

 described), follows the rule that the higher the absolute pressure the less 

 the artery expands with equal rises of pressure. 



Roy J found that in healthy arteries taken immediately after death 

 the increase of capacity with unit increase of pressure became pro- 

 gressively augmented up to a certain point, beyond which the increase 

 of capacity declined. The turning point he found to be about the 

 normal level of blood pressure in the animal from which the artery was 

 taken ; he formulated the conclusion that the arteries are most elastic 

 and distensible at pressures corresponding more or less exactly to the 

 normal blood pressures to which they were exposed during life (dog, 

 cat, rabbit, &c). 



In cases where there had been marked marasmus before death, Roy 

 found the arteries more distensible than normal arteries ; they expanded 

 most readily at lower pressures, and he sometimes found the maximum 

 distensibility to be immediately above zero pressure — as he found to be 

 normally the case with veins. 



Zwaardemaker§ found the augmentation of cubic capacity to be at 

 its maximum in the excised arteries of the horse and dog at 32 — 50 mm. 

 Hg. (very different figures from Roy's), in the ox at 100 — 150 mm. In 

 an experiment on a living artery in situ (dog) he concluded that the 

 maximum distensibility was at 75 — 100 mm.|| 



Thoma and Kaef er^I examined the increase of the diameter of certain 

 arteries (external iliac and common carotid of man). They found that 

 as the pressure was elevated the diameter increased rapidly at first, 

 then more and more slowly. 



Tigerstedt** calls attention to the discordant nature of these results, 

 and the need of further investigation. 



The relation of the cubic capacity of an artery to internal pressure 

 I have studied by the following method : — 



A portion of the artery to be examined was closed at one end by a 

 wooden plug firmly tied in ; into the other end a cannula of suitable 

 size was made fast, through which the artery could be subjected to any 



* ' Travaux de Laboratoire,' vol. 4, p. 178 (1880). 

 f Loc. cit. 

 % Loc. cit. 



§ 1 Nederlandsch. Tijdschrift voor Geneeskunde,' 2 Reeks, vol. 24, 1, pp. 61 — 76 

 (1838). 



|| Quoted in Tigerstedt's ' Lehrbuch des Kreislaufes ' (1893), p. 319. 



% * Arch, f . Path. Anatomie,' vol. 116, p. 9 (18S9). Cf. Luck, 1 Ueber Elasticities ■ 

 verhaltnisse gesunder u. kranken Arterienwand,' Inaug. Dissert., Dorpat, 1889; 

 Kacfer, 'Zur Methodik der Elasticitatsmessungen au der Gefasswand,' Inaug. 

 Dissert., Dorpat, 1891. 



** Loc. cit. 



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