140 LABORATORY MANUAL FOR ELEMENTARY ZOOLOGY 



g) Starch paste: stir up one gram of starch (corn starch or any commercial 

 product) in a small amount of cold water and pour slowly while stirring into 

 100 c.c. of boiling distilled water. Allow to boil for a few minutes. Dilute about 

 ten times for using. 



h) Glucose solution: 4 or 5 grams of glucose in a liter of distilled water. 



i) Fehling's solution consists of two solutions, not to be mixed until ready 

 to be used. First solution, 34.65 grams of copper sulphate made up to 500 c.c. 

 with distilled water. Second solution, 125 grams of potassium hydroxide and 

 173 grams of Rochelle salt (potassium sodium tartrate) made up to 500 c.c. 

 with distilled water. Keep separately in rubber-stoppered bottles. Just before 

 using mix in equal quantities, and shake until the blue precipitate formed is 

 completely dissolved, yielding a deep blue, clear solution. The assistant should 

 mix the solutions just before the laboratory period and give the students the 

 mixture. 



j) Saturated solution of barium hydroxide; should be clear. 



k) Physiological salt solution: dissolve 6 to 6j grams of pure sodium chloride 

 in a liter of distilled water. 



/) Aceto-carmine stain (Schneider's): to boiling 45 per cent glacial acetic 

 acid (45 c.c. pure glacial acetic acid plus 55 c.c. distilled water), add powdered 

 carmine until no more will dissolve, and filter. 



m) India ink suspension for feeding Paramecium: get solid carbon sticks, 

 obtainable in stores dealing in photographic supplies, as it is used for retouching, 

 and rub the stick in tap water until a moderately black suspension is obtained. 

 Do not use ordinary India ink as this may contain toxic substances. 



ri) Picro-acetic acid: i c.c. of pure glacial acetic acid, 99 c.c. of distilled 

 water; saturate the solution with picric acid crystals. 



0) Common salt. 



A small bottle containing each of these chemicals should be placed on each 

 table in the laboratory to avoid confusion. Needless to say, sugar, starch, and 

 enzyme solutions will not keep and must be made up fresh shortly before being 

 used. 



In addition to the above the assistant will require the following: 



Ether or chloroform. 



Chloral hydrate solution for macerating tissues of the frog. Weigh out 

 5 grams of chloral hydrate and add enough physiological salt solution to make 

 100 c.c. 



5. Section on general physiology. All of these experiments have been tried 

 repeatedly and have never been known to fail. No frog should be given out 

 that is not properly pithed, as it will certainly create a disturbance. The 

 assistant should thoroughly familiarize himself with the process of pithing. It 

 should always be done with a blunt instrument, not with a needle. Students 

 should be warned about letting the frog dry up. Commercial pepsin and 



