18 MATERIA MEDICA 



Red Poppy Petals . .18 



Arnica Flowers . . .20 



Chamomile Flowers . . 25 



Belladonna Leaves . .18 



Foxglove Leaves . . 20 



Henbane Leaves . . 20 



Thornapple Leaves . . 45 



Hemlock Herb . . 25 



Dandelion Root . . 22 



Liquorice Root . . 33 



Belladonna Root . . 38 



Sweet Flag Rhizome .. 25 



Colchicum Corm . . 34 



Couch Grass 40 



During the process of drying certain changes occur which are 

 produced, in part at least, by the action of enzymes contained in the 

 cells. These changes may affect the colour of the drug and so become 

 evident to the eye ; thus the scarlet of the red poppy petal becomes 

 dull violet, the green of leaves may turn to black, and gentian root, 

 which is normally white, may acquire a reddish brown colour. They 

 may also affect the odour of the drug ; thus vanilla pods, valerian roots, 

 orris rhizomes and other drugs acquire their characteristic odour during 

 the process of drying. They may also affect certain constituents 

 of the drug without producing any readily perceptible change ; thus 

 the gentiopicrin present in fresh gentian root may be completely decom- 

 posed. When the drug is quite free from moisture (not simply air- dry) 

 these changes cease and so long as the drug is kept quite dry they cannot 

 be resumed. The procedure adopted in drying drugs depends there- 

 fore upon whether the action of the enzymes is necessary and should 

 be encouraged or whether it is prejudicial and should be avoided. 

 In the former case slow drying and the maintenance of a temperature 

 at which the enzymes are most active are indicated (compare vanilla, 

 tea, cocoa, &c.). In the latter case the drying should be conducted 

 as rapidly as possible in order to render the enzymes inactive before 

 they have appreciably affected the constituents of the drug. Rapid 

 drying is accomplished by exposing the drugs in thin layers to a free 

 current of air at a temperature of about 35 to 40. They may be 

 scattered upon wire-netting trays (leaves not overlapping one another 

 and roots sliced longitudinally or transversely) and placed in a well- 

 ventilated loft ; or vertical columns of such trays, 6 or 8 inches apart, 

 may be formed in the open air and covered with roofing ; or the 

 trays may be assembled in a long narrow shed through which warm, 

 dry air is driven. Open-air drying is often resorted to in hot climates. 



Drugs that have been completely dried usually re-absorb about 

 10 per cent, of moisture when exposed to the atmosphere ; they are 

 then termed ' air-dry. 5 Even in air-dry drugs changes may occur ; 

 such changes are often prejudicial as they are for instance in Indian 

 hemp and foxglove leaves. In the case of Indian hemp the change 

 is probably simple oxidation of the cannabinol contained in it, but in 

 the case of foxglove leaves and many other drugs enzyme action is 

 certainly involved. 



Two methods of obviating such enzyme action may be adopted. 

 By the first the drugs are completely dried and maintained in that 



