86 HOW TO WORK 



subside in a conical glass, may be poured into a very narrow test 

 tube. Upon a glass slide being applied to the open end, the 

 tube may be inverted, and the deposit will gradually collect upon 

 the slide. The arrangement will be understood by reference to 

 fig. 146. 



According to either of the above methods any insoluble sub- 

 stances diffused through fluids can be easily collected for the pur- 

 poses of examination. In collecting shells of the diatomaceae for 

 microscopical examination they are often diffused through a con- 

 siderable quantity of water, allowed to subside, and obtained in the 

 manner above described. 



102. Examination of the Deposit. The deposit removed by the 

 pipette may be transferred to the thin glass, tinfoil, or Brunswick 

 black cell, 115 to 118, and submitted to examination in the micro- 

 scope. The animalcule cage, p. 66, will also be found very con- 

 venient for the examination of deposits from fluids, and it serves the 

 purpose of a compressorium when a very great amount of pressure is 

 not required. It is important that the shoulder of the animalcule 

 cage upon which the cover fits should be at least as wide as the one 

 figured in pi. XVIII, fig. 112, otherwise when the glasses are not 

 cleaned immediately after use, solutions which have been examined 

 are apt to dry and thus the removal of the cover without fracture 

 of the glass is very difficult. 



163. Wash-bottle. In many operations, especially in washing 

 deposits previous to microscopical examination and in filtration, the 

 wash-bottle used by chemists is of great use, as by it a stream of 

 water of any required degree of force can be easily directed to any 

 particular point, either for the purpose of washing away foreign 

 particles, or for removing part of the deposit itself. The wash-bottle 

 is also of great use in preparing sections of soft tissues for observa- 

 tion. It is made by inserting a cork into an ordinary half-pint bottle. 

 Through the cork pass two tubes, bent at the proper angle. The 

 longest terminates in a capillary orifice, while its other extremity 

 reaches down to the bottom of the bottle. The shorter tube reaches 

 only to the lower part of the cork, pi. XXII, fig. 143. By blowing 

 through the shorter tube, air is made to press upon the surface of 

 the water, which is thus driven up the longer tube and out at its 

 capillary orifice. 



The observer must have a stock of small titles, about two inches 

 in length and a quarter of an inch in diameter, such as homeopathic 

 globules are kept in, fig. 144, pi. XXII, and several small watch 

 glasses, of different sizes. 



