24 BIOLOGICAL PHYSICS 



the work of development, amid a matrix of nutritive 

 or organic material, which is little more than colloidal in 

 consistence, a work of comparative ease and precision, so 

 to speak, as, by the quasi-mechanical ballooning of cell 

 wall, of inter-cellular space, and of organised canal, it 

 affords a basis of physical support, on which even the 

 most delicate histological elements can be developmentally 

 dealt with with the least degree of confusion, and with the 

 greatest exactitude and safety ; while, after the conclusion 

 of embryonic development of the various textures and 

 organs constituting that stage of growth, it yields itself 

 still to the growing requirements of the post-embryonic 

 and foetal organism, by allowing the expansion and exten- 

 sion due to constant organic additions to take place by its 

 gradual and measured withdrawal or retirement, and by the 

 shrinkage and folding of its containing textures, until its 

 proportions are reduced to a "vestige of themselves," 

 and relegated to the nooks and corners and hidden recesses 

 of the central cerebro-spinal, or neural and hsemogenetic 

 organs. 



Amid all the vicissitudes through which this great fluid 

 element of the body passes it retains, in its physiological 

 condition, the characteristics of asepticity, and the power 

 of chemical and physiological preservativeness, on which 

 the condition of health is so inevitably and essentially 

 dependent. 



