36 



Scientific Proceedings (78). 



I wish to take this opportunity to express my appreciation of 

 the kindness of Professor J. L. R. Morgan of the department of 

 chemistry, Columbia University, who has given me the facilities of 

 his laboratory and has freely helped me with advice and criticism. 



23 (1201) 



The postural activity of the rectus abdominis muscle of the cat. 

 By F. H. Pike and Helen C. Coombs. 



[From the Physiological Laboratory of Columbia University.] 



If we accept Sherrington's 1 view that a muscle may undergo 

 changes in length without concomitant changes in tension as a 

 means of preserving a certain posture or attitude of the body, 

 we find that the rectus abdominis of the cat manifests this property 

 in a high degree. 



The animals used for experiment were etherized and a tracheal 

 cannula inserted. The skin was incised in the median line of the 

 thorax. The pectoral muscles of one side were then severed close 

 to their attachments to the sternum and sternal portions of the 

 ribs and reflected outward. The tendinous insertions of the rectus 

 abdominis on the ribs were divided and the free upper end lifted 

 out. A thread was tied about the tendinous end of the muscle 

 and led through a system of small pulleys to a muscle lever. The 

 abdominal wall was kept intact. A rise of the writing point of the 

 lever indicated a shortening of the muscle, while the writing point 

 fell when the muscle relaxed. The thoracic and abdominal 

 respiratory movements were recorded by Verdin tambours con- 

 nected to Crile stethographs. Small changes in the length of the 

 rectus abdominis occurred during ordinary respiration. But if 

 fluid, usually an M/8 solution of sodium chloride, was introduced 

 into the stomach through a stomach tube passed down the 

 esophagus, or directly into the peritoneal cavity through a hypo- 

 dermic needle, the muscle promptly relaxed, the amount of 

 relaxation being proportional to the amount of fluid introduced, 

 and continuing until the limit of distension of the abdominal 

 cavity was reached. This limit of distension is determined by 



1 Sherrington, Brain, 1915, Vol. 38, pp. 191-223. 



