222 EXPERIMENTAL PHYSIOLOGY. 



closing shock, it contracts again, so that the lever does not 

 immediately come to the abscissa. 



(e.) If the Morse key be rapidly tapped to interrupt the 

 primary current, the contractions become more or less fused, 

 and the lever remains above the abscissa writing a sinuous 

 line. 



4. Effect of Destruction of the Nervous System on the Heart 

 and Vascular Tonus. 



(a.) Destroy the brain of a frog, and expose its heart in 

 the usual way, taking care to lose no blood; note how red 

 and full the heart is with blood. 



(6.) Suspend the frog, or leave it on its back, introduce a 

 stout pin into the spinal canal, destroy the spinal cord, and 

 leave the pin in the canal to prevent bleeding. Observe 

 that the heart still continues to beat, but it is pale and 

 collapsed, and apparently empty, it no longer fills with blood. 

 The blood remains in the greatly dilated abdominal blood- 

 vessels, and does not return to the arterial system, so that 

 the heart remains without blood. If the belly be opened, 

 the abdominal veins are seen to be filled with blood. 



(c.) Amputate one limb, perhaps not more than one or 

 two drops of blood will be shed, while in a frog with its 

 spinal cord still intact, blood flows freely after amputation of 

 a limb. 



LESSON XLIX. 



PERFUSION OF FLUIDS THROUGH THE 

 HEART PISTON RECORDER. 



1. Perfusion of Fluids through the Heart. 



The Fluid (a.) Take two volumes of normal saline, add 

 one volume of defibrinated sheep's blood, mix, and filter. 

 See that the blood is thoroughly shaken up with air before 

 mixing it. This is the best fluid to use. 



