88 The Microscope. 



will do you no good, for 3''ou cannot see the creatures. What 

 3''our eye will notice will be innumerable indistinct streaks zig- 

 zagging across the field in all directions and with lightning 

 speed. Without exception, the motion of these little animals 

 is the most rapid, the most bewildering, the most astonishing of 

 any movement that the microscope can exhibit. Before you 

 can say " It lightens," the animal has come and flashed out of 

 sight. Yet at times a single one may encourage you only t© 

 disappoint; it will apparently attach one end of its little, cork 

 screw bod}'- to a ciliated cell or other object in the field and 

 there rotate on its long axis with a rapidity that gives it the 

 appearance of a vibrating cord, or of a long, narrow, ghostly 

 ellipse, that after a moment's pause to vibrate thus and to excite 

 a hope in the microscopist's heart, simply disappears. Where 

 it goes or how I defy any human microscopist to say, be his 

 eyes ever so well cultivated and trained. 



This agile parasite is said to be an animal, being classed 

 among the Infusoria. It was discovered by M. Certes in the 

 alimentary canal of the European oyster, and named Trypano- 

 soma Balbianii. The European and the American parasites are 

 identical, although the American and the European oyster 

 belong to diflfereut species. 



Fortunately the active creatures can be easily killed and 

 without in the least changing their form or structure. If the 

 microscopist has the time and patience to wait until the Try- 

 panosoma shall die under the cover, he will need no reagent ; 

 but he will have neither the time nor the patience. Therefore, 

 kill. Take the ordinary, dilute acetic acid to be had of the 

 druggist and dilute it by the addition of an equal bulk of water. 

 Add a drop of this liquid at the edge of the cover glass and it 

 will kill the parasites as soon as it touches them, and without 

 the slightest change in their character, except that to the weary- 

 eyed microscopist they seem peculiarly quiet when they are 

 dead. 



As they were leaping and zig-zagging across the field they 

 appeared so like the common Spirilla, those animated cork- 

 screws to be had from any ditch, that you may at once decide 

 they are Spirilla. Others have made the same excusable mis- 

 take. The action of the two forms is so similar and the para- 

 sites are so indistinctl}" visible while alive, that to call them 



