476 APPENDIX 



the left ventricle to the foot less the time required for its passage from 

 the ventricle up the carotid. Measure as nearly as possible these two 

 distances. Calculate the pulse- wave speed from these data in meters 

 per second. 



Compare this result with the blood's speed. 



Expt. 29. Demonstration of the Actual Circulation in the Frog's Foot. 

 (Apparatus: Compound microscope, stand-rod, clamp, two long, wide 

 slides, wax,' small clips, green frog, cloth, tea-lead.) Pith the frog's 

 brain and wrap the animal excepting one foot rather tightly in the cloth 

 and tea-lead previously wet in water. Support the frog and stretch out 

 his exposed foot over the two slides placed one over the other and held 

 in the cork-lined clamp just over the microscope's stage. Secure an 

 outer toe in each of the clips and separate the clamped slides until the 

 web of the foot is stretched over the opening in the stage, catching the 



FIG. 262 



b 



Diagrammatic section of the alveolar wall of a frog's lung: a, a, capillary spaces; 

 6, epithelial cells; c, muscle-fibers in the alveolar partitions. -(F. E. Schulze.) 



clips on the outer edges of the slides. Use a 2-inch objective to find the 

 best spot where the web is flat and level, the circulation lively, and the 

 web free of pigment-cells if possible. Study with the No. 3 objective. 

 (See also page 304.) 



Observe how the. speed and redness of the blood are proportional to 

 the diameter of the vessel. See the shape and multitude of the erythro- 

 cytes and the shape and fewness of the (smaller) leukocytes. (Com- 

 pare the red corpuscles with those of man.) Note the constancy of the 

 flow, at least after the shock of the pithing has passed off. 



Such a preparation is often good for two days. 



The phenomena of inflammation may be studied by applying a weak 

 solution of mustard oil or of croton oil to the web. The action of adrena- 

 lin also should be observed a drop of 0.01 per cent, saline solution 

 being applied. 



V. RESPIRATION. 



Expt. 30. The Pneumatics of External Respiration. (Apparatus: 

 the schema of the respiration.) A. Normal Breathing. Lower the 

 diaphragm rhythmically and note how the finger-cot lung fills with air 

 falling into it through the open glottis. Observe the slight changes of 

 pressure in the two manometers. What is it that expands the lung? 



B. Asphyxia. Push the glass plug into the glottis, thus closing the 

 respiratory opening to the exterior. Now the lung no longer fills as the 



