44 MANUAL OF HISTOLOGY. 



acid drop by drop until the solution is faintly acid to the 



taste. 



Action of alkalies upon the blood. Take a drop of the 

 newt's blood and mount it in a drop of serum or of salt solu- 

 tion. Then, affixing a strip of bibulous paper in the way that 

 has been described, add drop by drop a weak solution of aqua 

 ammonise. A similar strip of paper, somewhat larger in size, 

 upon the other side, will cause a current and carry the corpus- 

 cles to the side of the field where the paper strip is largest, and 

 there the corpuscles may be observed at rest, and the altera- 

 tions effected by the alkali duly noted. It will be seen that 

 after a little time the corpuscles, both red and colorless, will 

 swell up and finally, after a time, provided the alkali be in 

 sufficient amount, disappear or become so expanded as to be 

 invisible. Sometimes they will burst, leaving the field evenly 

 stained with a homogeneous glutinous-looking substance. 



Action of electricity. It seems to make little difference, so 

 far as the microscope is concerned, whether the continuous or 

 interrupted current is employed, as in either case the phe- 

 nomena observed are the same- in quality. Take bits of tin- 

 foil and attach them to an ordinary glass slide, in such a 

 way that they are just % inch distant from one another. The 

 pieces of foil should be triangular in shape and have their 

 pointed extremities turned to one another. The specimen 

 should be a drop of newt's blood diluted with an equal amount 

 of serum, both perfectly fresh. They should be intimately 

 mixed with a glass rod. 



Depositing a drop of this solution upon a cover-glass, it 

 should be inverted and placed upon the slide in such a way 

 that it occupies an intermediate position between the bits of 

 tin-foil. The ordinary stage clips of the microscope are then 

 to be used in holding the slide firmly in position and to press 

 upon the tin-foil. The only remaining task is the attaching of 

 conducting wires from the electrical instrument, one to each 

 clip. The bits of tin-foil are easily fastened to the slide ; they 

 have merely to be hammered out flat, when they will adhere by 

 simple pressure. Sometimes it may be desirable to approxi- 

 mate the poles. In such cases it is necessary to use two fine 

 bits of platinum wire. They should be flattened, and shaped 

 like the letter S. Rest them upon the bits of tin-foil, opposite 

 to one another and at the required distance apart. The cover- 



