BLOOD-PRESSURE IN THE CAPILLARIES. 



245 



them on a whetstone, or heating slightly in a gas-flame. Tie a 

 piece of india-rubber on the other end, and the cannula is 

 complete. 



3. Blood-Pressure in the Capillaries. 



(a.) Make the following apparatus (Fig. 112), consisting 

 of a slip of glass, 2 cm. long, 3 to 4 mm. broad, and 1 mm. 

 thick, and on its under surface fix with cement a glass plate 

 (a), with a surface of 5 mm. square. Two threads supporting 

 a paper scale-pan are attached to the glass plate. Place the 

 glass plate (a) over the skin on the dorsal surface of the 

 finger, just at the root of the nail. Add weights to the 

 scale-pan until the skin becomes pale. Note the weight 

 necessary to bring this about, but observe that the skin does 

 not become pale all at once. 



(6.) Test how altering the position of the hand affects the 

 pressure in the capillaries. 



Fig. 112. Apparatus 

 used by v. Kries for 

 estimating the capil- 

 lary blood-pressure. 



Fig. 113. Posterior Pair of Lymph-Hearts 

 (L) of the Frog. 



4. Examine with a microscope the circulation in the web of a 

 frog's foot, or in the mesentery of a frog with its brain destroyed, 

 and afterwards slightly curarised. 



