THE CHEMISTRY OF THE ANIMAL BODY. 517 



feces belonging to the period before the meal, and the period subsequent to it. 

 Carbon unites directly with hydrogen, oxygen, and sulphur only. 



Carbon Monoxide, CO. — This gas is a product of the incomplete combus- 

 tion of carbon, is present in illuminating gas, and burns on ignition to carbon 

 dioxide. 



Properties. — A colorless, odorless gas. Inspired, it unites with the blood 

 to form a carbon-monoxide haemoglobin (Hb-CO). This is a very stable 

 bright-red compound which may even be boiled without decomposing. Ani- 

 mals poisoned with CO die from want of oxygen, since the latter cannot dis- 

 place the carbon monoxide from combination with haemoglobin. Carbon 

 monoxide poisoning is accompanied by diabetes 1 probably because of de- 

 creased power to burn sugar. 



Carbon Dioxide, C0 2 . — This is the highest oxidation compound of carbon, 

 the product of its complete combustion. It is present in the air to the extent 

 of 0.04 per cent. It is formed in all living cells, and in higher animals is 

 collected by the blood and brought to the lungs and skin for excretion ; it is 

 also a product of putrefaction ; it gives an acid reaction to herbivorous urine. 

 It is found dissolved in all natural waters, and is present combined in sea 

 shells. It is found in the blood principally combined with sodium in the 

 serum, and is likewise combined with calcium and magnesium in the bones. 



Preparation. — (1) By burning carbon or a carbon-containing substance, 

 C 6 H 12 6 + 120 == 6C0 2 + 6H 2 0. 



Sugar. 



(2) By heating a carbonate, 



CaC0 3 =CaO+C0 2 . 



(3) By the action of an acid on a carbonate, 



Na 2 CO s + 2HC1 — 2NaCl + C0 2 + H 2 0. 



In the blood, haemoglobin and, to a less extent, serum-albumin and primary 

 sodium phosphate act like acids. If the gases be extracted from fresh defib- 

 rinated blood in a vacuum, all the C0 2 is removed. If sodium carbonate be 

 added to blood, the carbonic acid belonging to this is likewise given up in a 

 vacuum, while a simple aqueous solution of sodium carbonate is not affected. 

 If serum be extracted in vacuo, only a little more than half the carbonic acid 

 contained in it is dissociated from combination, indicating that in the previous 

 experiment haemoglobin had acted like an acid. If a solution of bicarbonate 

 of sodium (NaHC0 3 ) be exhausted under the air-pump, just one-half of the 

 C0 2 is given off, sodium carbonate (Na 2 C0 3 ) remaining. In the serum more 

 than one-half of the C0 2 is obtained in vacuo, because the serum-albumin, 

 like the haemoglobin, though less effectively, acts like an acid in fixing the 

 alkali and liberating the gas. There is likewise present the action of pri- 

 mary phosphate on the acid carbonate, 



NaH 2 P0 4 + NaHCO, = Na 2 HPO, + H 2 -f CO, 



1 Straub: Archiv fur experimentelle Pathologie wnd Pha.rmakol»<jic, ls'iti, l:<]. :;s, s. |:><J 



