306 EUFHORBIACEjE. 



sudden immunity and the critical subsidence of fever in certain 

 acute diseases, such as pneumonia, measles, &c., which he 

 considei-s may also be regarded as indicating the establishment 

 of an immunity in those diseases. 



Animals in which an immunity to the ricin poison had been 

 established, were found, -six months after the cessation of all 

 treatment, to be incapable of being affected by the poison. 

 Ehrlich has also made similar experiments with abrin, the 

 active principle of Abrns jyrecatorius, which he reserves for 

 early publication. 



Description. — There are many varieties of the plant 

 which have been produced by cultivation ; they may be divided 

 into the large red- seeded kinds, and those with grey seeds 

 marked with brown blotches; the latter are preferred for 

 medicinal use. 



^ 



The roots are tolerably straight, and give off a few rootlets ; 

 they are covered by a light-brown bark, nearly smooth, but 

 riiarked with little transverse warty ridges. The wood is white 

 and soft. The bark lias an acrid taste^ 



The seeds are contained in a tricoccous capsule, one in each 

 cell ; they are oblong, from ^ to | an inch long and about ^ of 

 an inch broad, the dorsal surface is more arched than the 

 ventral. The apex is somewhat pointed, below it is a tumid 

 caruncula, on the removal of which a dark depressed cicatrix is 

 seen. The testa is grey, marked with brown blotches. The 

 kernel is enclosed in a delicate white membrane, and consists of 

 a copious white albumen, in the axis of which are situated two 

 leafy cotyledons and a short stout radicle. 



M 

 1 



Microscopic structure. — The epidermis of the seeds is com- 

 posed of tabular cells, which are here and there coloured in 

 patches which correspond to the spots on the seed. The testa 

 consists of cylindrical cells in close apposition. The kernel 

 is a mass of closely-packed cells with granular contents, but if 

 water is brought in contact with the section, oil globules separate 

 from the albumen. In the latter may be demonstrated the 



