i 5 o 



Microscopical Essays. 



Of Animalcula in Infusions, Sec. 



Thefe require little or no preparation. The firft object is to 

 procure them, the fecond to render them vifible by the micro- 

 fcope. A few obfervations, however, may be of ufe. Many- 

 drops of water may be examined before any can be found ;. fo 

 that if the obferver be too hafly, he may be eafily difappointed, 

 though other parts of trie fame water may be fully peopled by 

 them. 



The furface of infufed liquors is generally covered with a thin 

 pelicule, which is eafily broken, but acquires thicknefs by (land- 

 ing ; the greatefl number of animalcula are generally to be found 

 in this fuperfioial film* 



In fome cafes it is necefiary to dilute the infufions ; but this is 

 always to be done with diftilled water, and that water mould be 

 examined in the microfcope before it is made nfe of: the neg- 

 lect of this precaution has been a fource of many errors. 



Animalcula are in general better obferved when the water is a 

 little evaporated, as the eye is not confufed, nor the attention 

 diverted by a few objects. To feparate one or two animalcula 

 from the reft, place a fmall drop of water on the glafs near that 

 of the infufion ; make a fmall neck, or gutter, between the two 

 drops with a pin, which will join them together ; then the inftant 

 you perceive that an animalcuium has traverfed the neck or gutter, 

 and entered the drop, cut off the communication between the 

 two drops. 



