34 LEAVES 



the only purgative ones. The total amount of methylanthraquinone 

 derivatives present in senna has been variously estimated at TO to 

 4-0 per cent, a proportion that is not consistent with the purgative 

 action of the drug and the true active constituent is apparently still 

 unknown. 



Recent investigations have revealed the presence of oxymethylanthra- 

 quinones in a number of laxative drugs, which, therefore, form a natural group 

 allied by the similarity of their constituents. The following are the most im- 

 portant members of the group : 



Senna, which contains aloe-emodin, and rhein. 



Cascara Sagrada, the bark of Rhamnus Purshianus, de Candolle (N.O. 

 Rhamnacece), which contains emodin and frangula-emodin. 



AlderbucJcthorn Bark, from Rhamnus Frangula, Linne, which contains frangulin 

 and frangula-emodin. 



Rhubarb, the rhizome of Rheum ojficinale, Baillon, &c. (N.O. Polygonacece), 



which contains or yields chryso- 

 phanic acid, emodin, aloe- 

 emodin, and rhein. 



Aloes, from various species 

 of Aloe (N.O. Liliacece), which 

 contains and yields aloe-emodin. 

 Cassia Pulp, an aqueous ex- 

 tract of the fruit of Cassia 

 Fistula, Linne, which contains 

 unidentified oxymethylanthra- 

 quinones. 



FIG. 22. Argel leaves. A, showing the shape of US6S. Senna stimulates 

 the leaf ; B, c, D, showing the curled ap- the muscular COat of the 

 pearance of the dried leaves. Natural size, intestine and produces purg- 

 ation, which is not followed, 



as is commonly the case, by constipation ; it is therefore one of the 

 most useful of purgatives, especially in cases of habitual constipation. 



Substitutes, &C. Senna pods, the fruits of Cassia acuti folia ; occa- 

 sionally found mixed with the senna, and imported as a separate article 

 of commerce ; very flat legumes. (Seep. 100.) 



Cassia obovata (dog senna) , Upper Egypt ; formerly highly valued 

 as a drug, and cultivated in Italy and sometimes termed Italian 

 senna ; leaves broadly obovate, apex abruptly tapering venation, 

 pinnate, distinct ; constituents similar to those of senna ; total 

 oxymethylanthraquinones 3 '8 per cent. ; about equal to senna 

 in activity. The leaves are sometimes broken up and mixed with 

 broken Alexandrian senna, they may be recognised by the papillose 

 cells of the lower epidermis. 



Argel leaves, Solenostemma Argel, Hayne (N.O. Asclepiadece) ; re- 

 semble senna in colour and outline, but distinguished by their thick, 

 rigid texture and peculiarly curled, curved, or twisted appearance ; 



