16 THE GENERAL PRINCIPLES OF THE METHOD 



window it will be seen that the surface of the jelly 

 over which the cells have passed is studded with 

 corpuscles. 



If the jelly has been properly made the slide may 

 be handled freely. It may be tilted to any angle, and 

 even turned upside down without the cover-glass sliding 

 off or the jelly becoming displaced. This is a fortunate 

 fact, because it enables the microscope to be placed 

 at any convenient angle for examination of the slide 

 or for purposes of photography. If the specimen is 

 quickly focused under the microscope while the 

 spreading-out process of the cells is going on, using 

 a ^-inch objective and, say, a No. 4 eye-piece, the 

 picture presented is a very remarkable one. The cells 

 will be seen rushing along in a direction from the 

 centre of the cover-glass towards its margin; they 

 tumble over each other, leucocytes and red cells, 

 lymphocytes and blood-platelets, bumping into each 

 other and apparently all striving to reach some imagin- 

 ary goal. Gradually the flow T becomes slower and 

 slower, the cells cease to "barge" into each other so 

 fiercely, they squeeze past one another, and it will be 

 realized what a marvellous power blood-corpuscles 

 have of accommodating their shapes to almost any 

 requirements. 



Leucocytes and red cells all behave in the same 

 way. They allow r themselves to be squeezed through 

 gaps between other cells, which appear to be so small 

 that if it had not actually been seen one never would 

 believe it. As the flow becomes slower it will be 

 seen that suddenly a passing leucocyte goes "ashore"; 



