IMMUNITY AN ADAPTATION 47 



the problems before us is to study first the phenomena of in- 

 dividual acquirement of properties. Only when we have gained 

 some knowledge of the factors operative in cases of individual 

 acquirement can we with any security proceed to discuss the 

 inheritance of acquired characters. 



Now it is in respect to these new acquirements in the higher 

 animals that we obtain the deepest insight into the process 

 involved, and that through the abundant, not to say overwhelm- 

 ing, studies of the last quarter of a century upon immunity. 

 There is a vast literature upon this subject. Some of the most 

 notable achievements in science, both of the last and of the 

 present century, have been in this province of immunity : the 

 names of the great workers in this domain are known to all 

 men — of Pasteur, Koch, Behring, Roux, Metchnikoff, Ehrlich, 

 Almroth Wright. Tuberculin, diphtheria antitoxin, and the 

 arrest of typhoid fever by inoculation are matters about which 

 every intelligent being is supposed to know something ; they 

 are even common subjects of conversation at the dinner-table, 

 be it in London or Glasgow, in Washington or Seattle, in Johannes- 

 burg, Dawson City or Adelaide. Yet I do not know of a single 

 general biologist who has dwelt adequately upon their significance 

 in this connexion. 



For consider the following facts and think what they signify. 

 There is a certain bean, known as the Jequirity or prayer bean, 

 the seed of Ahrus precatorius, from which a highly active and 

 highly poisonous principle can be extracted, abrin, which has 

 been resolved into two proteins, an albumose and a globulin, 

 both, when injected into animals, producing symptoms of like 

 nature. A closely allied active principle, ricin, is obtainable 

 from the castor oil plant, and this has been carefully studied by 

 Professor Cushny, 1 who has determined that in this case the 

 toxic substance is a globulin, and this so powerful that one gram 

 is adequate to kill one million and a half guinea-pigs, with necrosis 

 of the tissues at the site of injection, acute congestion, inflamma- 

 tion and oedema of various tissues. It is significant that the 

 action is not immediate : the animals appear to be in good 

 health for four or five days ; then symptoms supervene suddenly 

 and there is death in a very short period. There is in short a 



1 Arch. f. exp. Pathol. x\i., 1898, 439 ; see also in conjunction Osborne and 

 Mendel, Am. Journ. of Physiol, x., 1904, 36. 



