366 



MANIPULATION. 



external, is, perhaps, one of the most wonderful objecta that 

 can be seen by the microscope; the large blood corpuscles 

 may even be traced as far as the extremities of the toes, but 

 the circulation in the branchiae is the most striking, as there 

 the large capillary vessels are directly under the influence of 

 the heart's action, and the movement of the corpuscles is not 

 continuous but synchronous with that of the pulsation of the 

 ventricle. In large newts, the circulation can only be 

 examined In the tail ; for this purpose, it will be necessary to 

 confine them to a piece of glass or a long cell, by means of a 

 bandage of tape ; but the tail being vertical, instead of hori- 

 zontal, the body must be kept firmly fixed, otherwise the tail 

 cannot well be secured. Some persons place the animal in a 

 glass tube with water, but unless there is some contrivance 

 under it like Mr. Varley's dark chamber, the vessels cannot be 

 seen distinctly. With fish, the plan the author has found 

 most convenient is exhibited by figs. 238 and 239 ; in fig. 238, 



Fig. 238. 



a b represents a plate of glass about three inches lono-, and an 

 inch-and-a-half wide, upon which is cemented a glass cell, d 

 having a long oval cavity, c, deep enough to contain an ordinary 

 sized stickleback ; to the under surface of the bottom plate of 

 glass, at the corners, are cemented, as shown by fig. 239, four 



strips of plate-glass, 

 ^-riMiiKlITTn^"l^^aiiiiiiiiiMri about a quarter-of- 



an-inch wide, after 



the plan shown at c ,• 

 Fig. 239. these serve to raise 



the bottom plate in 

 such a manner that when the trough is laid on the stao-e of 

 the microscope, the bandage, d, will not interfere with its 



