NITROGEN EXHALED FROM THE LUNGS. 



39 



This occurrence of iron is full of signifi- 

 cance in regard to the formation of the 

 blood. 



12. In the action of the gastric juice on 

 the food, no other element takes a share, 

 except the oxygen of the atmosphere and 

 the elements of water. This oxygen is in- 

 troduced directly into the stomach. During 

 the mastication of the food, there is secreted 

 into the mouth from organs specially des- 

 tined to this function, a fluid, the saliva, 

 which possesses the remarkable property of 

 enclosing air in the shape of froth, in a far 

 higher degree than even soapsuds. This 

 air, by means of the saliva, reaches the sto- 

 mach with the food, and there its oxygen 

 enters into combination, while its nitrogen 

 is given out through the skin and lungs. 

 The longer digestion continues, that is, the 

 greater resistance offered to the solvent ac- 

 tion by the food, the more saliva, and con- 

 sequently the more air enters the stomach. 

 Rumination, in certain graminivorous ani- 

 mals, has plainly for one object a renewed 

 and repeated introduction of oxygen; for 

 a more minute mechanical division of the 

 food only shortens the time require I for 

 solution. 



The unequal quantities of air which reach 

 the stomach with the saliva in different 

 classes of animals explain the accurate ob- 

 servations made by physiologists, who have 

 established beyond all doubt the fact, that 

 animals give out pure nitrogen through the 

 skin and lungs, in variable quantity. This 

 fact is so much the more important, as it 

 furnishes the most decisive proof, that the 

 nitrogen of the air is applied to no use in 

 the animal economy. 



The fact that nitrogen is given out by the 

 skin and lungs, is explained by the property 

 which animal membranes possess of allow- 

 ing all gases to permeate them, a property 

 which can be shown to exist by the most 

 simple experiments. A bladder, filled with 

 carbonic acid, nitrogen, or hydrogen gas, if 

 tightly closed and suspended in the air, loses 

 in 24 hours the whole of the enclosed gas ; 

 by a kind of exchange, it passes outwards 

 into the atmosphere, while its place is occu- 

 pied by atmospherical air. A portion of 

 intestine, a stomach, or a piece of skin or 

 membrane, acts precisely as the bladder, if 

 filled with any gas. This permeability to 

 gases is a mechanical property, common to 

 all animal tissues ; and it is found in the 

 same degree in the living as in the dead 

 tissue. 



It is known that in cases of wounds of 

 the lungs a peculiar condition is produced, 

 in which, by the act of inspiration, not only 

 oxygen but atmospherical air, with its whole 

 amount (ths) O f nitrogen, penetrates into 

 the cells of the lungs. This air is carried 

 by the circulation to every part of the body, 

 so that every part is inflated or puffed up 

 with the air, as with water in dropsy. This 

 state ceases, without pain, as soon as the 

 entrance of the air through the wound is 



stopped. There can be no doubt that the 

 oxygen of the air, thus accumulated in the 

 cellular tissue, enters into combination, while 

 its nitrogen is expired through the skin and 

 lungs. 



Moreover, it is well known that in many 

 graminivorous animals, when the digestive 

 organs have been overloaded with fresh juicy 

 vegetables, these substances undergo in the 

 stomach the same decomposition as they 

 would at the same temperature out of the 

 body. They pass into fermentation and 

 putrefaction, whereby so great a quantity 

 of carbonic acid gas and of inflammable 

 gas is generated, that these organs are enor- 

 mously distended, sometimes even to burst- 

 ing. From the structure of their stomach or 

 stomachs, these gases cannot escape through 

 the oesophagus ; but in the course of a few 

 hours, the distended body of the animal be- 

 comes less swollen, and at the end of twenty- 

 four hours no trace of the gases is left. (25.) 



Finally, if we consider the fatal accidents 

 which so frequently occur in wine countries 

 from the drinking of what is called feather- 

 white wine (der fedetfaveisse Wein,^ we can 

 no longer doubt that gases of every kind, 

 whether soluble or insoluble in water, pos- 

 sess the property of permeating animal tis- 

 sues, as water penetrates unsized paper. 

 This poisonous wine is wine still in a state 

 of fermentation, which is increased by the 

 heat of the stomach. The carbonic acid gas 

 which is disengaged penetrates through the 

 parietes of the stomach, through the dia- 

 phragm, and through all the intervening 

 membranes, into the air-cells of the lungs, 

 out of which it displaces the atmospherical 

 air. The patient dies with all the symptoms 

 of asphyxia caused by an irrespirable gas ; 

 and the surest proof of the presence of the 

 carbonic acid in the lungs is the fact, that the 

 inhalation of ammonia (which combines 

 with it) is recognized as the best antidote 

 against this kind of poisoning. 



The carbonic acid of effervescing wines 

 and of soda-water, when taken into the sto- 

 mach, or of water saturated with this gas, ad- 

 ministered in the form of enema, is given out 

 again through the skin and lungs ; and this 

 is equally true of the nitrogen which is in- 

 troduced into the stomach with the food in 

 the saliva. 



No doubt a part of these gases may enter 

 the venous circulation through the absorb- 

 ent and lymphatic vessels, and thus reach 

 the lungs, where they are exhaled ; but the 

 presence of membranes offers not the slight- 

 est obstacle to their passing directly into the 

 cavity of the chest. It is, in fact,' difficult 

 to suppose that the absorbents and lympha- 

 tics have any peculiar tendency to absorb 

 air, nitrogen or hydrogen, and convey these 

 gases into the circulation, since the intestines, 

 the stomach, and all spaces in the body not 

 filled with solid or liquid matters, contain 

 gases, which only quit their position when 

 their volume exceeds a certain point, and 

 which, consequently, are not absorbed. 



