140 PRACTICAL HISTOLOGY [XVII 



inflammation, and the stages between the early dilation 

 ( 7, a) and stagnation ( 7, c) may conveniently be 

 followed. Note under a high power 



a. The elongated platelets and the spherical white 

 corpuscles increase in number in the peripheral zone of 

 the arteries and veins, if the current is quick enough to 

 show a peripheral zone ; the white corpuscles often roll 

 over along the wall. 



b. In the veins, and to a less extent in the 

 capillaries, the platelets and white corpuscles cling to 

 the walls, at first for a time only, later permanently. 

 Here and there a mass of adhering corpuscles forms 

 which stretches across the tube ; sometimes this is torn 

 away by the current, sometimes it blocks the vessel 

 and causes stagnation. Note in the stagnated vessels 

 the gradual obliteration of the outlines of the cor- 

 puscles. 



c. If the circulation is fairly rapid, pinch a small vessel with 

 fine pointed forceps and note the way in which the platelets 

 stick to the injured spot. 



d. Focus the side of a small vein in which the circulation is 

 slow, and look amongst the white corpuscles adhering to the 

 wall for one which projects a little externally. Draw this at 

 intervals of 15 minutes to note its rate of migration. 



10. Circulation of blood in the newt. A newt is given you 

 without brain and curarised. Mesentery. The hole in the stage 

 should be small, about 1 to 1'5 cm. long, and '5 to '75 cm. broad. 

 The method is the same as in the frog ( 9). 



Pancreas. The skin and abdominal wall are cut through on 



