STATICS AXD DYNAMICS OF THE BODY. 895 



But it is difficult to understand how this could happen in an organ apparently 

 uninsulated, for its membranous envelope is as good a conductor as moist tis- 

 sues or water. Another theory supposes that static electric currents, similar 

 to those which are detected in muscular tissue, but of a far more powerful 

 kind, are constantly circulating through these organs ; and that the equilib- 

 rium of such currents being disturbed by some action of the nervous system, 

 a discharge of the electric force then takes place. In accordance with this 

 view, the organs themselves, with their vascular cell-walls, seem constructed 

 for a special purpose, being unlike any other known animal organ ; after re- 

 peated discharges, time must be allowed for the restoration of the power of 

 giving shocks ; and, lastly, the electric force is precisely proportioned to the 

 general activity of the nutritive functions. Moreover, a difference has been 

 observed in the character of the discharge or shock, between the Torpedo and 

 the Gymnotus, a difference connected with peculiarities in the structure of 

 their electric organs. The shock is more powerful in the Gymnotus, the piles 

 of cells of the organ being extremely long ; whereas in the Torpedo the shock 

 is less powerful, and the piles of cells are shorter. It has been supposed, by 

 some, that the so-called nerve-force is directly converted, in these organs, into 

 electric force ; and the further inference has been drawn, that the two forces 

 are hereby shown to be identical. The former hypothesis may be correct, 

 but the latter opinion is not so (p. 232). The two forces are so far related, 

 that either most easily excites the other. The ultimate source of the electric 

 power is chemical action, most probably oxidation. 



STATICS AND DYNAMICS OF THE HUMAN BODY. 



Physiology is not sufficiently positive or perfect, as a science, to 

 have its exact constants. But we may here collect certain numerical 

 expressions concerning the specific gravity, height, and weight of the 

 body; the weights of its various organs; the relative quantities of its 

 chief proximate chemical constituents ; also, concerning the weight of 

 the daily food, and its proportion to the weight of the body ; its proxi- 

 mate constituents, and the relations of these to the proximate constit- 

 uents of the body; their destination in the economy; and the effects 

 of deprivation of food. 



Besides this, we may examine, in a general manner, the chemical work 

 performed within the body ; and endeavor to estimate, numerically, its 

 vito- chemical processes, and their relation, on the one hand, to the 

 food, drink, and air, and, on the other, to the mechanical and calorific 

 work performed in, and by, the system. The nutritive, electric, and 

 nervous work, may also be here again noticed. 



STATICS OF THE HUMAN BODY. 



Specific Gravity of the Body. 



The specific gravity of the body depends upon that of its various 

 tissues and organs. Essentially, all the materials of the body, with 

 the exception of the fatty substances, are heavier than water, and the 

 mean specific gravity of all the tissues is higher than that of water. 

 But the air retained in the lungs during life, even the residual and re- 

 serve air, is just sufficient to counterbalance the higher specific gravity 

 of the body generally, and so enables it to float (p. 183). 



The specific gravities of the chief tissues are given in p. 70 ; that of 



