1901.] Properties of the Arterial avid Venous Walls. 133 



None of these workers seem to have taken into account the possible 

 conditions of contraction and relaxation, or to have been aware of the 

 existence of post-mortem contraction at all. 



The method I have employed is an old one with certain modifica- 

 tions. The strip is firmly held by a clamp at one end, and suspended 

 in the vertical position ; the other end of the strip is made to pull 

 upon the lever of a Helmholtz myograph, the attachment being made 

 relatively near the fulcrum — the extension of the strip is magnified 

 six times by the movement of the writing point. The lever is directed 

 at right angles to the circumference of the smoked drum and its point, 

 therefore, moves in a straight line perpendicular to the direction of move- 

 ment of the recording surface. A simple arrangement on Pfliiger's plan 

 — somewhat similar to that figured by C. C. Stewart* — is employed to 

 keep the writing point in constant contact with the smoked paper. 

 The successive elongations are represented by vertical lines upon a 

 stationary drum, which was each time moved round a certain distance 

 by hand. 



Short strips (commonly 5x5 mm.) of the arterial wall were used in 

 order that the angular movement of the lever should not exceed a small 

 limit. The successive weights were allowed to pull upon the strip for 

 equal periods — varying in actual duration in different experiments — 

 most commonly for 1 minute. Increments of 20 grammes were used in 

 all the experiments of which tracings are given, except where otherwise 

 specified. Drying of the strips was prevented by frequent pencilling 

 with defibrinated blood, serum, or salt solution (0*75 per cent.). 



Very different results were obtained with (1) strips taken from large 

 arteries like the aorta and pulmonary artery, with their highly elastic 

 walls, and relatively scanty muscular tissue ; and (2) strips taken from 

 medium-sized arteries like the carotid, &c, with their strong muscular 

 coat. 



Transverse and Longitudinal Strips from the Aorta and Pulmonary 

 Artery. — Both longitudinal and transverse strips were taken from the 

 walls of these vessels (chiefly from the sheep), and the results obtained 

 quite agree in a general sense with those described by Wertheim, Roy, 

 and others. The greatest amount of extension is produced by the first 

 addition of weight, and successive additions of weight cause diminish- 

 ing increments in length per unit increase of weight. A line joining 

 the bases of the extensions is a curved line concave to the axis or 

 abscissa. (Figs. 12 — 15.) 



Strips from Medium-sized Arteries (Carotid, &c.). — Strips cut longi- 

 tudinally and transversely to the long axis of the artery were 

 employed, and certain differences were evident in the behaviour of 

 the two kinds. But much more striking and important differences 

 are shown by strips obtained from contracted arteries as compared 

 * * American J ournal of Physiology,' vol. 4, p. 186. 



