474 A. W. BELLAMY 
Teratological developments certainly have a number of fea- 
tures in common regardless of how or in what organisms these are 
induced: One of these features is differential susceptibility, a 
differential that bears a very definite relation to the ‘physiological 
axes’ of the organism. This means simply that different regions 
of the physiological axes of organisms show different degrees of 
susceptibility to certain concentrations of action of a variety of 
physical and chemical agents. Observations by Child and _ his 
students on some two hundred. species of organisms, including 
representatives from all the principal animal phyla and a con- 
siderable number of plants, agree in showing, at least in the 
simpler organisms and in the early stages of development of 
higher forms, that those regions of the egg or embryo that dif- 
ferentiate earliest and grow most rapidly, or simply the most 
active regions of the organism, are most susceptible to conditions 
that seriously affect developmental or functional processes. 
Several methods are available for demonstrating these differences 
in susceptibility,? the differential appearing, according to experi- 
mental conditions, as a differential disintegration gradient 
associated with death, as differential inhibition, as differen- 
tial acceleration, or as differential acclimation or recovery in 
development. 
The fact that such a wide variety of organisms, both plant and 
animal, characteristically exhibits a differential susceptibility to 
a considerable number of external agents and conditions (cya- 
nides, anesthetics, acids, alkalies, certain electrolytes, several 
alkaloids, extremes of temperature, lack of oxygen, et al.) indicates 
at once that there is something fundamentally similar in the _ 
organismic pattern existing in these different protoplasms. It 
must mean that organismic pattern, as distinguished from the 
2 Differences in susceptibility along the axes of organisms are demonstrable 
as: 1) differences in survival time of one region of the organism as compared 
with other regions, under conditions that kill slowly without permitting acclimation 
to occur; 2) as differences in the degree of inhibition of growth and development, 
or in certain cases as differences in the degree of acceleration of these processes; 
3) as differences in the rate or degree of acclimation to a certain range of less 
severe conditions; 4) as differences in the rate or degree of recovery after tem- 
porary exposures that inhibit development. See also Child, ’20, p. 154. 
