SEMEN PHYSOSTIGMATIS. 193 



is lodged ; and he has arrived at the conclusion that its seat is the 

 gmnular protoplasmic particles, which alone acquire an orange tint by 

 the action of weak caustic alkalis. 



Chemical Composition — Jobst and Hesse ^ proved in 1863 that 

 the poisonous nature of Calabar bean depends upon an alkaloid, to which 

 they gave the name Physostigmine. It is obtained by the method 

 generally adopted for extracting analogous substances, that is, by preci- 

 pitating one of its salts from an aqueous solution by bicarbonate of 

 sodium, and dissolving out the base with ether or benzol. As extracted 

 by these chemists, physostigmine is an amorphous mass of decidedly 

 alkaline reaction, soluble in much water and in acids. On exposure to 

 the air the solution soon becomes red, or sometimes intensely blue, a 

 partial decomposition of the alkaloid taking place. The red coloration 

 may even be observed in the aqueous infusion of a few cotyledons. It 

 disappeare by sulphuretted hydrogen or sulphurous acid, but returns if 

 these reducing agents are allowed to evaporate. 



Hesse - ascertained (1867) that physostigmine consists of (^H^'N^O*; 

 he now obtained it perfectly colourless and tasteless, softening at 

 40° C, fusing at 45", but not supporting a heat of 100° C, without 

 decomposition, which is manifested b}^ a red coloration. 



In 1865 Yee and Leven,* by treating the powdered unpeeled seed 

 in nearly the same way, prepared an alkaloid which they called Eseriiie. 

 It differs from Hesse's physostigmine in that it forms colourless, rhom- 

 boidal, tabular crj-stals of a bitter taste, melting at 90° C. It dissolves 

 easily in ether, alcohol, or chloroform, but very sparingly in water. The 

 last named solution is alkaline, and reddens by exposure to the air. 



It is assumed by some writere, as Tison,* that eserine is only the 

 pure form of physostigmine ; but at present we feel hardly warranted in 

 admitting the identity of the two substances. 



Harnack and Witkowski in 1876 ascertained the presence of 

 another alkaloid in the seed, which they called CalabaHiie. It is nearly 

 insoluble in ether and also very different from physostigmine in its 

 physiological action, but somewhat similar to strychnine. Calabarine 

 is consequently not to be found in those preparations of calabar bean 

 which have been obtained or purified by means of ether. 



Hes.se (1878) exhausted the cotyledons of Physostigma with petro- 

 leum ether, and obtained crystals of a new indifferent substance 

 O*H"0 + 0H-, which he called Phytostenn. It is closely allied to 

 Cholesterin, but, in its solution in chloroform, devoid of rotatory power 

 and melting at 133°. Cholesterin melts at 145°, and deviates, in its 

 ethereal solution, the ray of polarized light to the left. Phytosterin also 

 occurs in peas; Hesse suggests that the crystallized appearance of 

 alkaloids as prepared by former observers was perhaps due to 

 phytosterin. 



From the cotyledons per se, cold water extracts mucilage, precipit- 

 able by neutral acetate of lead. The watery infusion contains also 

 albumin, which may be coagulated by heat or by alcohol. The infusion 

 is colourless, does not redden litmus, nor does it contain sugar in ap- 



* Liebig's Annalen der Chem. «, Pharm. March 1867, 149. 



129 (1864) 115. 3 Comptes Rendus, Ix. (1865) 1194. 



2 Ibid. 141 (1867) 82 ; Chem. Netca, 22 *Op. ciL chap. 2. 



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