24 PASTORAL AND AGRICULTURAL BOTANY 



LABORATORY EXERCISES 



1. Place a thin transverse section of the endosperm of Strychnos Nux-vomica on a 

 slide and treat with a few drops of sulphuric acid, if strychnin is present there will 

 be a red coloration of the cell-contents. Place a small crystal of potassium chromate 

 beneath the cover-glass and a violet color will be produced. 



2. Place a thin transverse section of the rhizome of the monk's hood, Aconitum 

 Napellus, on a slide and treat with a few drops of 50 per cent, sulphuric acid. A carmine 

 red coloration will appear and this is a specific reaction of aconitin found in the paren- 

 chyma surrounding the vascular bundles. This reaction is more intense, if the sections 

 have been previously warmed in a sucrose solution. 



3. The- presence of cyanogenetic glucosides may be detected as follows: Crush the 

 part of the plant in water and set aside for some time, then filter and add to the 

 filtrate a little silver nitrate. If hydrocyanic acid is present a white precipitate is 

 formed. 



4. Place thick sections of the plant tissue to be examined in a 5 per cent, alcoholic 

 solution of potash for about a minute then transfer to a solution containing 2.5 per 

 cent, ferrous sulphate and i per cent, ferric chloride and keep at about 6oC. for ten 

 minutes. Then treat the section with dilute hydrochloric acid (one part strong acid 

 to six parts of water) for five to fifteen minutes, if hydrocyanic acid is present a blue 

 precipitate of Prussian blue appears. 



5. Guignard's test may be used as an alternative with four. White filter-paper is 

 dipped in a i per cent, solution of picric acid and dried. When ready to be used moisten 

 the treated papers with a 10 per cent, solution of sodium carbonate and again dry. 

 These test papers should be kept in stoppered bottles. Exposed to the fumes of hydro- 

 cyanic acid the paper rapidly changes to an orange-red color as the test is a delicate 

 one. 



EXPERIMENTAL PHARMACOIOGY 



Experiments on the Action of Veratrin (See Greene, Charles Wilson, Experimental 

 Pharmacology. A Laboratory Guide for the Study of the Physiological Action of 

 Drugs, third edition, P. Blakiston's Son & Co., 1909, page 50 and fig. on page 51. This 

 book may be taken as a guide in such experiments. As the time for this course is 

 limited such experimental work should be performed as a class demonstration by the 

 professor and his assistant, rather than as individual student exercises. The work 

 below should be performed as a sample. 



1. Veratrin on the frog. The dose for a frog is about 0.5 c.c. of a i per cent, solution 

 of the fluid extract of Veratrum viride, or 0.3 c.c. of o.oi per cent, veratrin. Compare 

 with the effects of aconite and barium. See experiment 4. 



2. Veratrin on the mammal. Give a cat or rabbit i c.c. of o.i per cent, veratrin 

 hypodermically, or i c.c. of i per cent, for a dog. Keep under observation for a con- 

 siderable time. 



3. Veratrin on the heart strip. Subject the contracting strip of ventricle to 0.005 

 to 0.05 per cent, veratrin in saline. 



