306 SECRETS OF ANIMAL LIFE 
most interesting contribution of the book is the 
discussion of what Professor Adami calls “ the law 
of habit.” Once the cells of the body of a rabbit 
have got accustomed to producing a counteractive 
or anti-toxin to ricin (from the castor-oil plant), 
they may go on producing anti-ricin for weeks or 
months after the original stimulus. In the horse 
a single toxin unit of tetanus can lead in the process 
of immunization to the production of 1,000,000 anti- 
toxin units. Ptyalism may persist for a year after 
a dose of mercury. A cold in the head may con- 
tinue for weeks after the causative agent has dis- 
appeared and thorough sterilization of the nose has 
been effected. The cells form a habit, it may be 
an entirely new habit, and it lasts, “an acquired 
cell variation becoming, if 1 may so express it, 
converted into a cell heredity.” In somewhat 
the same way we may speak of microbes acquiring 
new habits, for the indifferent bacillus may become 
pathogenic, and the virulent may be tamed. But 
the difficulty is to pass from generations of cells 
and of unicellulars to the very different case of 
generations of multicellular animals. And even if 
we suppose, with Professor Adami and others, that 
the peculiarly modified body-cells give off specific 
metabolites, or hormones, or messengers of some 
sort, which eventually reach their goal in the germ- 
cell and thus specifically affect the offspring—say 
in the direction of becoming innately immune to 
some poison—can one say that this is as yet more 
than a ballon d’essa? 
