274 EXPERIMENTAL PHYSIOLOGY 



8. Process of Inflammation. Remove the cover-glass, dry the 

 web with filter paper and touch a point with a pin dipped into a 

 2 per cent, solution of croton oil and olive oil. Without replacing 

 cover glass, with low power, observe whether the presence of the 

 croton oil effects any change in the diameter of the vessels, or in 

 the rate of blood-flow. If there is a change in both, has one a causa- 

 tive relation to the other? Note and describe minutely all changes 

 which take place at or near the place touched with the croton oil. 

 If no marked changes have been produced in 10 minutes by the 

 croton oil, touch the point with a needle which has been dipped 

 in strong nitric acid. Observe with high power, using cover-glass. 

 Describe process of extravasation of white or red corpuscles. 



^Lymph-Heart^. 



Another method of pertorn 

 results. The tongue of a pith 



are readily seen. A drop of x> 



produce the necessary inflamn ation. 



ng this experiment also gives good 

 d frog is pinned out over a hole in 



a board. With the proper d( gree of stretching the bloodvessels 



ol on the surface of the tongue will 



1. Posterior Lymph-Hearts. Stretch the pithed frog out, 

 ventral side down, and watch the beating of the posterior pair of 

 lymph-hearts. These hearts are located (at the dorsal posterior 

 end of the body) one on each side of the urostyle in the triangular 

 spaces easily observed there between certain muscle attachments. 



Cautiously turn back the skin covering the lymph-hearts being 

 careful not to injure the cutaneous veins and thus cause bleeding. 

 Moisten exposed parts with normal salt solution when necessary, 

 and count the number of beats per minute of each lymph-heart. 

 Compare. The movements of the blood-heart can be distinguished 

 without opening the chest. Can you detect any synchronous 

 relation between the rhythm of the blood-heart and that of the 

 lymph-hearts? 



Blood-heart. 



1. Blood heart-of the Frog. Expose the blood-heart. Observe 

 the heart "in situ" noting the two auricles; the ventricle; the 

 auriculo-ventricular groove; and the truncus arteriosus, which pro- 

 jects anteriorly from the ventricle in front of the auricles and 

 divides into the two aortae. 



