• STiiYCHNINE SULPHATE 381 



they improve the local tone of the alimentary canal ; prob- 

 ably by exciting the various spinal centres. Strychnine 

 also stimulates the intestinal muscular tunic and therefore 

 increases peristaltic action. 



Circulation, — Strychnine excites the heart muscle and 

 motor ganpjlia, and thus makes the cardiac pulsations more 

 forcible. Large doses diminish the frequency of the frog's 

 heart, and produce diastolic pauses. Blood tension is 

 heightened by medicinal doses, through stimulation of the 

 medullary vasomotor centres. Toxic quantities cause vaso- 

 motor paralysis and fall of arterial tension. Experiments 

 conducted with blood (Harley) containing strychnine, shaken 

 with air for 24 hours, resulted in the blood yielding about 

 one-third more oxygen and one-half less carbonic dioxide, 

 than blood, minus strychnine, similarly treated. Harley 

 concluded that strychnine arrests oxidation in the body, 

 but there is no physiological evidence that such is the case 

 in life. 



Nervous System and Muscles. — Strychnine is essentially 

 a spinal stimulant. Many ingenious experiments conclu- 

 sively prove that the principal effect of strychnine (convul- 

 sions) is produced by direct stimulation of the cells of the 

 inferior cornua. The alkaloid also appears to cause dilata- 

 tion of the arterioles in the spinal cord. 



Two experiments only may be presented. The first 

 proves that the action of strychnine in producing convul- 

 sions is of spinal origin; the second that the alkaloid acts 

 upon the inferior cornua. 



1. When strychnine is placed directly upon the spinal 

 cord of a frog, after the blood has been withdrawn from the 

 body, and allowed to diffuse through its substance, convul-. 

 sions occur. These are limited, at first, to those muscles 

 whose nerves have their insertion nearest the point of 

 application of the poison, and then they progress as the 

 alkaloid continues its path of absorption through the cord. 



2. When every part of a frog below the second cervical 

 vertebra has been removed, save the nerves, muscles and 



