1010 AN AMERICAN TEXT-BOOK OF PHYSIOLOGY. 



For further discussion of carbohydrates in the body see under the indi- 

 vidual sugars, and under Fat in the Body. 



BENZOL DERIVATIVES OR AROMATIC COMPOUNDS. 

 The aromatic compounds are characterized by a configuration in which six 

 atoms of carbon are linked together in a circle called the benzol ring. The 

 type of this is benzol, a hydrocarbon found in coal-tar and having the formula, 

 H 



c 

 / \ 



H C C H 



II I 



H C C H , 



\ // 



C 4 



H 



The hydrogen atoms may be substituted for others, substitution of one OH 

 group, for example, forming phenol, C 6 H 5 OH. If, however, two OH 

 groups are substituted, three different bodies, corresponding to the different 

 arrangements on the ring, become possible. If the two OH groups occupy 

 the positions 1 and 2 the substance is or/io-dioxybenzol ; if 1 and 3, meta- 

 dioxybenzol ; and if 1 and 4, para-dioxybenzol. 



It is possible to convert bodies of the fatty series into those of the aro- 

 matic. Acetylene passed through red-hot tubes yields benzol. On the other 

 hand, aromatic bodies may be converted into those of the fatty series. If 

 phenol in aqueous solution be subjected to electrolysis by an alternating cur- 

 rent under which circumstances hydrogen and oxygen are alternately liberated 

 on the same pole, the effect of this intermittent oxidation and reduction is to 

 break up the phenol into caproic acid, and finally, after passing through acids 

 of lower carbon contents, into carbonic acid and water. 



The aromatic compounds found in the urine are normally exclusively 

 derived from the products of proteid putrefaction in the intestines. It is 

 admitted that neither fats nor carbohydrates play any part in their formation. 



Benzol, C 6 H 6 . This body if fed is absorbed and afterward converted into oxybenzol 

 or phenol, with subsequent behavior similar to phenol. 



Phenol (Carbolic Acid, Oxybenzol, Phenyl-hydroxide), C 6 H 5 OH. 

 This is an aromatic alcohol. A 5 per cent, solution precipitates proteid, and a 

 much weaker solution produces irritation of the tissues, and especially those 

 of the kidney, where its excretion takes place. It is strange that a strong 

 antiseptic like phenol should be a normal product of proteid putrefaction. 

 Phenol is obtainable from tyrosin, by processes of cleavage and oxidation (see 

 Tyrosin), and in the intestinal canal is probably derived from tyrosin. A 

 small amount of the phenol ordinarily absorbed is converted by the organism 

 into pyrocatechin, a dioxybenzol. These two substances are found in normal 

 urine in ethereal combination with sulphuric acid, C 6 H 5 O.SO 2 .OH (or as an 

 alkaline ethereal sulphate). This synthesis, accomplished by the union of the 



