7 he Comparative Physiology of the Suprarenal Capsules. 69 



Fig. 3. 



Carotid atrn . 



7M/, / 35 K. 

 if fcL, Atropine. 



Injt ctt d / c.c. of e. r-t ract of 

 s i i/t! mi rials o feel (/ ii r ?5) . 

 Signal. 



Tinu tracing (seconds). 



Control experiments with extracts of " head-kidney " and muscle 

 of fishes always gave negative results. 



Perfusion Experiments. — These have been performed upon large 

 toads. A cannula was tied into one aorta, the ligature also including 

 the other. A snip was made in the sinus venosus, and then normal 

 saline (0*6 — 0*9 per cent.) or Ringer's circulating fluid was perfused 

 through the blood-vessels from a funnel placed about 9 to 12 inches 

 above the animal. The toad was held in a suitable holder, and the 

 fluid which ran through was collected in graduated cylinders and 

 measured at the end of every five minutes. I have performed eleven 

 of these experiment with practically uniform results. It will only 

 be necessary to give the details of two typical ones. 



In other experiments an extract made from the lymphatic "head- 

 kidney " of different Teleosts was perfused, and also one made from 

 muscle of various fishes. Both these always gave negative results 

 when properly filtered. 



In Experiment 1 it will be noticed that the interrenal gives a very 

 definite result, though not so marked as that of the medullary 

 glands. This point will be referred to again immediately. It is 

 clear from Experiment 2 that extracts of the suprarenal bodies of 

 Teleosts are inactive as regards the flow of fluid through the blood- 

 vessels of a toad. 



f J 



