186 EXOGONIUM PURGA 



mentioned, is now applied to a resin which is soluble in ether. 

 Convolvulin is a glucoside, being resolvable by moderate heating 

 with emulsin, or dilute acid, into sugar, and a crystallizable 

 substance called Convolvulinol. Convolvulin when pure is colour- 

 less, and readily dissolves in alcohol or the fixed alkalies ; but is 

 insoluble in ether, or ammonia, or in oil of turpentine. 



ADULTEEATIONS AND SUBSTITUTIONS. In consequence of the 

 increased demand for official jalap combined with a falling off 

 in the supply from its original source, jalap has of late years been 

 frequently adulterated by being intermixed with the roots of other 

 plants, but the characters given above of true jalap are such as 

 will readily distinguish it. The roots of two plants which are 

 extensively used as adulterants of, or substitutes for, the official 

 jalap, require, however, some notice from us ; these are Tampico 

 Jalap and Woody Jalap. 



1 . Tampico Jalap, as its name implies, is imported from Tampico, 

 a port to the north of Vera Cruz, in the Gulf of Mexico. Han- 

 bury traced its botanical source to Ipomtea simulans. Tampico 

 jalap agrees with true jalap in odour and taste, and pieces may 

 be found which also resemble it in other respects, but it may be 

 generally distinguished from the genuine drug by its more 

 shrivelled appearance, lighter weight, smaller size, and more 

 elongated and tapering form. Tampico jalap yields from 10 to 

 15 per cent, of a resin, which in its pure state is entirely soluble 

 in ether. This resin therefore differs from Convolvulin, the principal 

 constituent of crude jalap resin, which is insoluble in ether. 

 Tampico jalap is generally regarded as inferior in medicinal 

 activity to the official jalap, but we have no very accurate informa- 

 tion on this point. It is imported in large quantities into this 

 country and elsewhere. 



2. Woody Jalap or Orizaba Root, or as it is also termed Light, 

 Fusiform, or Male Jalap, or Jalap Tops or Stalks ; is derived 

 from the neighbourhood of Orizaba, and its botanical source is 

 Ipomaa orizabensis, Ledanois. It is generally found in irregular, 

 angular or circular pieces, which are clearly portions of a large 

 root ; or sometimes the smaller roots are found entire, and are 



