38 OF LIFE, AND ITS CONDITIONS. 



it was supposed that every exertion of muscular power involved a metamor- 

 phosis of the tissue of the muscle itself, sufficient in its amount to produce 

 the mechanical equivalent of the heat that would be otherwise liberated by 

 the combustion of its Hydrocarbon. But the observations of MM. Fick 

 and Visliceuus on the increase of the urea and other nitrogenous products 

 of the disintegration of muscle, which shows itself in the Urine during and 

 after prolonged muscular exertion confirmed, as they have been, by the 

 results of many similar inquiries seem to place it beyond doubt that the 

 amount of Motor energy put forth is so completely out of proportion to that 

 of the muscular tissue which we can suppose to have been consumed, that 

 we cannot do otherwise than attribute it in great part to the oxygeuation of 

 the uou-azotized components of the Blood during its passage through the 

 muscle. What is the peculiar condition which determines this oxidation, is 

 at present undetermined ; but it would seem not improbably related to the 

 electric changes of which (as will be shown hereafter) the contracting muscle 

 is the seat. 



20. The case seems different; however, in regard to the generation of 

 Nerve-force ; for there is great reason to believe that its production is 

 mainly, if not entirely, dependent upon the oxygenation of the Nerve-sub- 

 stance itself. Its rapid metamorphosis, particularly in the cortical substance 

 of the brain, is indicated alike by many histological characters, and by the 

 appearance of the special products of that metamorphosis in the Urine; 

 where the quantity of the alkaline phosphates, whose production may fairly 

 be attributed to the oxidation of the phosphorized fats of the nerve-tissue, 

 bears a very close relation to the quantity of Brain-work executed. The 

 enormous supply of Blood which the Brain receives as much as one-fifth 

 part of the whole Arterial stream being sent to an organ whose weight does 

 not exceed one-fortieth that of the entire body is another evidence of the 

 activity of the changes continually in progress between the Blood and the 

 Nerve-substance. We may roughly liken the Brain to a Galvanic battery, 

 and the Blood to its exciting liquid. When the circuit is closed, a rapid 

 oxygenation of the Nerve-substance, as of the zinc of the battery, takes 

 place ; and a corresponding equivalent of Nerve-force (which seems closely 

 related to, but not identical with, Electricity) is generated. But the Blood 

 also serves for the nutritive renewal of the Nerve-substance in its intervals 

 of repose; thus supplying it with the "potential energy," which is con- 

 verted into "actual energy" by the oxygeuation that destroys it as a living 

 tissue. How intimate is the dependence of the generation of Nerve-force 

 011 the supply of Blood to the Brain, is proved by the effect of its suspen- 

 sion ; for if this be complete, there is an immediate cessation of conscious- 

 ness and motor power. And that this cessation of activity is due rather to 

 the want of the Oxygen supplied by the Blood, than to that of its nutrient 

 material, appears from the recent experiments of Professor Bert, of the Col- 

 lege do France. For having, by means of an apparatus capable of includ- 

 ing the entire human body, and of being exhausted of its air to auy re- 

 quired degree, brought on the faintuess and exhaustion proceeding even 

 to a state resembling asphyxia which is known as the inal dc* )>iunf<t</ii<'x, 

 he found that this was immediately and completely relieved by the inspira- 

 tion of air highly charged with oxygen. And two aeronauts, MM. Croce- 

 Spinelli and Bivel, having inspired from bags containing such a mixture, 

 found themselves in possession of their consciousness and power of exertion, 

 under a diminution of pressure which had reduced Messrs. Glaishcr and 

 Coxwell to a state of insensibility. 1 



1 Comptes Rendus, March 30tl), 1874. 



