Response of Arteries to Blood Serum and Plasma. 87 



a. That the process of clotting liberates a vasoconstrictor 

 substance which acts on the coronaries, the renal vessels and the 

 limb vessels. It acts directly on the muscle coat and it is not a 

 proteid body. 



63 (672) 



General physiological properties of diaphragm muscle. 

 By FREDERIC S. LEE and A. E. GUENTHER. 



[From the Department of Physiology, Columbia University.] 



Strips of the diaphragm of the cat, both curarized and non- 

 curarized, have been excised after death and experimented with 

 in moist chambers at room temperature. Their great resistance is 

 demonstrated by the facts that they remain irritable two to three 

 times longer than, and do several times the amount of work done 

 by, a leg muscle, such as the extensor longus digitorum. Moreover, 

 the diaphragm is not paralyzed by curare until long after the leg 

 muscles have ceased to act. A most striking phenomenon is the 

 tendency of the diaphragm strips to yield rhythmic twitches. This 

 is much more pronounced than with the control leg muscles. It 

 may be made manifest by the action of solutions of certain electro- 

 lytes, where the twitches are irregular in extent and duration ; and 

 by weak faradic currents, which insure more regular responses. 

 With 40 to 100 faradic stimuli in the second, the twitches occur 

 at a rate of from 2 to 4. They are much more marked in non- 

 curarized muscle. When irregularities due to the stimulated 

 current are excluded, the following factors may possibly interact 

 in the production of the rhythmic responses: (1) There may be 

 present the Wedenski effect; (2) the weak stimulus may affect 

 from time to time different groups of fibers within the muscle, the 

 irritability of the groups varying; (3) polarizing factors may be 

 present. The relations of these and other possible factors are 

 not yet established. A strip of diaphragm muscle as a whole has 

 a decided power of rhythmical response, but it is not yet certain 

 whether this power is possessed by the individual muscle fibers. 



