Charles Manning Child

Crile reports that Child showed experimentally, by testing susceptibility to poisons and narcotics, that gradients exist along the main axes of whole organisms and of single cells⁴. Crile adds that Child saw such gradients as a possible expression of functional polarity, in some cases perhaps only a graded difference in metabolic rate. In the 1924 book, polarity and symmetry are described as non-specific, quantitative regional differences within a specific protoplasm⁵. Because the axis is a gradient, it can be altered or removed by many different agents, according to how susceptible each level is⁵.

Loeb records that Child used rapid disintegration of tissue without oxygen, or with cyanide, as a general test. Younger animals disintegrated faster than older or larger ones, and Child built a theory of senescence on this². Loeb did not doubt the observations but disputed the reading. He suggested that softer membranes in the young, perhaps linked to chemical constitution such as calcium content, could explain the faster disintegration without a higher metabolism³.

The 1924 book was planned with a colleague as one of two companion works, this one on the general physiological foundations of behavior and the other on neurological foundations⁸. Later writers kept returning to Child's ideas. A planarian regeneration review lists Child's gradient model among the historical gradient models that preceded positional information theory⁶. Levin cites Child's 1915 book when arguing that organism status, like cognition, is not a binary property⁷.