THEORY OF RESPIRATION. 



77 



wheel, this stop-cock opens when the whee 

 moves slower, and closes more or less com- 

 pletely when the wheel moves faster than is 

 required for a uniform motion. When i 

 opens, more steam is admitted, (more force,^ 

 and the motion of the machine is accele- 

 rated. When it shuts, the steam is more or 

 less cut off, the force acting on the piston- 

 rod diminishes, the tension of the steam in- 

 creases, and this tension is accumulated for 

 subsequent use. The tension of the vapour, 

 ojr the force, so to speak, is produced by 

 change of matter, by the combustion of 

 coals in the fire-place. The force increases 

 (the amount of steam generated and its ten- 

 sion increase) with the temperature in the 

 fire-place, which depends on the supply of 

 coals and of air. There are in these engines 

 other arrangements, all intended for regula- 

 tion. When the tension of steam in the 

 boiler rises beyond a certain point, the pas- 

 sages for admission of air close themselves; 

 the combustion is retarded, the supply of 

 force (of steam) is diminished. When the 

 engine goes slower, more steam is admitted 

 to the cylinder, its tension diminishes, the 

 air passages are opened, and the cause of 

 disengagement of heat (or production of 

 force) increases. Another arrangement sup- 

 plies the fire-place incessantly with coals in 

 proportion as they are wanted. 



If we now lower the temperature at any 

 part of the boiler, the tension within is di- 

 minished; this is immediately seen in the 

 regulators of force, which act precisely as 

 if we had removed from the boiler a certain 

 quantity of steam (force.) The regulator 

 and the air-passages open, and the machine 

 supplies itself with more coals. 



The body, in regard to the production of 

 heat and offeree, acts just like one of these 

 machines. With the lowering of the ex- 

 ternal temperature, the respirations become 

 deeper and more frequent; oxygen is sup- 

 plied in greater quantity and of greater den- 

 sity; the change of matter is increased, and 

 more food must be supplied, if the tempera- 

 ture of the body is to remain unchanged. 



It is hardly necessary to mention, that in 

 the body the tension of vapour cannot, any 

 more than an electrical current, be consi- 

 dered the cause of the production offeree. 



From the theory of disease developed in 

 the preceding pages, it follows obviously, 

 that a deceased condition once established, 

 in any part of the body, cannot be made to 

 disappear by the chemical action of a re- 

 medy. A limit may be put by a remedy 

 to an abnormal process of transformation; 

 th^t process may be accelerated or retarded; 

 but this alone does not restore the normal 

 (healthy) condition. 



The art of the physician consists in the 

 knowledge of the means which enable him 

 to exercise an influence on the duration of i 

 the disease ; and in the removal of all disturb- 

 ing causes, the action of which strengthens | 

 or increases that of the actual cause of i 

 disease. 



It is only by a just application of ite prin- 

 ciples that any theory can produce really 

 beneficial results. The very same method 

 of cure may restore health in one individual, 

 which, if applied to another, may prove fatal 

 in its effects. Thus in certain inflammatory 

 diseases, and in highly muscular subjects, 

 the antiphlogistic treatment has a very high 

 value; while in other cases blood-letting 

 produces unfavourable results. The vivify- 

 ing agency of the blood must ever continue 

 to be the most important condition in the 

 restoration of a disturbed equilibrium, which 

 result is always dependent on the saving of 

 time ; and the blood must, therefore, be con- 

 sidered and constantly kept in view, as the 

 ultimate and most powerful cause of a last- 

 ing vital resistance, as well in the diseased 

 as in the unaffected parts of the body. 



It is obvious, moreover, that in all dis- 

 eases where the formation of contagious 

 matter and of exanthemata is accompanied 

 by fever, two diseased conditions simulta- 

 neously exist, and two processes are simul- 

 taneously completed ; and that the blood, as 

 it were by re-action (i. e. fever) becomes a 

 means of cure, as being the carrier of that 

 substance (oxygen) without the aid of which 

 the diseased products cannot be rendered 

 harmless, destroyed, or expelled from the 

 body; a means of cure by which, in short, 

 neutralization or equilibrium is effected. 



IV. THEORY OF RESPIRATION. During 

 the passage of the venous blood through 

 the lungs, the globules change their colour; 

 and with this change of colour, oxygen is 

 absorbed from the atmosphere. Further 

 or every volume of oxygen absorbed, an 

 equal volume of carbonic acid is, in mosi 

 cases, given out. 



The red globules contain a compound of 

 ron; and no other constituent of the body 

 contains iron. 



Whatever change the other constituents 

 of the blood undergo in the lungs, thus 

 much is certain, that the globules of venous 

 )lood experience a change of colour, and 

 hat this change depends on the action of 

 oxygen. 



Now we observe that the globules of arte- 

 rial blood retain their colour in the larger 

 vessels, and lose it only during their pas- 

 sage through the capillaries. All those con- 

 stituents of venous blood, which are capable 

 of combining with oxygen, take up a cor- 

 responding quantity of it in the lungs. Ex- 

 >eriments made with arterial serum have 

 shown, that when in contact with oxygen 

 it does not diminish the volume of that gas. 

 Venous blood, in contact with oxygen, is 

 reddened, while oxygen is absorbed; and a 

 corresponding quantity of carbonic acid is 

 formed. 



It is evident that the change of colour in 

 the venous globules depends on the combi- 

 nation of some one of their elements with 

 oxygen ; and that this absorption of oxygen 

 is attended with the separation of a certain 

 quantity of carbonic acid gas. 



G* 



