1901.] 



Properties of the Arterial and Venous Walls. 



125 



from the body. Sertoli found its excitability to persist 5, 6, or 

 even 7 days after excision — especially when kept in blood-serum at a 

 temperature of 5 — 8° C. The muscle shortens very markedly on 

 cooling and relaxes on warming to about 40° ; then remains unchanged 

 in length up to 50° ; it is killed between 40 and 50°. Slow rhythmic 

 contractions may appear when cooled from 40 to 35°, even 2 or 3 days 

 after excision. 



In a very recent paper, De Zilwa* describes the shortening of the 

 muscle by cooling down to 10 or 15° C, gradual relaxation up to 40° 

 (when it is complete), spontaneous contractions developing at 38° absent 

 at 40°. On further raising the temperature he notes contraction at 

 47° or 48° ; later, relaxation beginning at 52 — 54° and completed at 

 58 — 60°. The muscle is often found to retain some trace of excitability 

 when beginning to relax at 52 — 54° ; when the relaxation is complete 

 the muscle is dead, and its response to excitation or changes of 

 temperature cannot be restored by cooling. There is no evidence of 

 the occurrence of true rigor mortis in this muscle. 



The unstriped muscle of the cat's bladder also maintains its excita- 

 bility for relatively long periods. 



C. C. Stewartf finds that at ordinary room temperatures, irritability 

 often lasts 24 — 48 hours after excision; kept in an ice-box at 5 — 8°, 

 one preparation responded to the Faradic current at the end of 4 days. 

 When cooled a strip of the bladder muscle shortens, the shortening- 

 being complete about 10° C. When the temperature is raised from 

 this point it relaxes up to about 40°, above 40° there is shortening 

 (slowly at first, then more rapidly) up to 53 — 57°, where the muscle 

 apparently loses its excitability and dies. A distinct loss of tone, often 

 of considerable extent, follows ; the muscle is comparatively relaxed 

 and very soft. Only when the temperature is raised to 69° does what 

 Stewart describes as the shortening of heat-rigor occur. 



The essential correspondence of the main features presented by these 

 living muscles and by a contracted artery under the influence of 

 temperature changes is too obvious to need insisting upon. 



Many years ago, Samkowy| found that the unstriped sphincter 

 pupillae muscle of the rabbit contracts at first on warming, but 

 dilates later; when relaxed by warmth, cooling to 28 — 29° induces 

 contraction, The dilated pupil of a dead cat contracts at moderate 

 temperatures and dilates when the temperature is raised to about 37°. 

 Using also the rectococcygeus muscle of the rabbit and the bladder 

 of the cat, rabbit, &c, he concluded that unstriped muscle relaxes at 

 about 37°. 



* ' Journal of Physiology,' vol. 27, p. 200. 

 f 'American Journal of Physiology,' vol. 4, p. 199 (1900), 

 X ' Pfliiger's Archiv,' vol. 9, p. 400 (1874). 

 VOL. LXX. K 



