826 APPENDIX. 



Organic Chemical Substances. 



Nearly all of the most important substances found in the animal body 

 have been mentioned and described in the preceding pages. It will be 

 only necessary here to add some brief notes. 



Certain terms have been used without explanation. 



Hydrocarbons. Compounds of carbon and hydrogen. Carbon 

 being a tetrad element, the simplest hydrocarbon is C iv H 5 4 , methane or 

 marsh gas. It is found in the gases of the alimentary canal (intestines) 

 (p. 406). It is the first of the series known as paraffins. The different 

 members of the series increase by CH , so that the next paraffin is 

 C H 6 , ethane; C a H^ propane, and so on. The general formula being 



C n H 2 n + 2 - 



Alcohols. From a hydrocarbon, by substituting OH (hydroxyl) for 

 H, we obtain the corresponding alcohol ; thus from CH 3 H we obtain 

 CH 3 OH, methyl alcohol; from C a H 8 H, C 2 H 6 OH, ethyl alcohol; from 

 C 3 H 7 H, C 3 H 7 OH, propyl alcohol and the like. They are hydrates of 

 the hydrocarbons. 



Ethers. The ethers are obtained from their corresponding alcohols 

 by dehydration; e.g., 2(C 2 H 6 ) OH - H 2 = (C 2 H 6 ) 2 0, ethylic ether. 



Aldehydes. The aldehydes are obtained by oxidation of alcohols 

 thus : C 2 H 5 OH + = CH 3 COH -f H 2 , ethyl aldehyde. 



Acids. The acids are obtained by further oxidation, one atom of 

 being substituted for H o , e.g., CH 3 CO OH, .acetic acid. 



The series of acids obtained from the first series of paraffins is known 

 as fatty acids ; those which are most familiar as fatty acids being 

 C 4 H^0 , butyric* acid; C ( .H ]0 , caproic acid; C 1C H 32 2 , palmitic, and 

 C 18 H 3f 2 , stearic, derived from C 4 H 10 (butane), C 6 H ]4 (hexane), C 16 H 34 

 (hecdecane), and C lr< H 3R , respectively. 



Soaps and Fats. The fatty acids in combination with soda or 

 potash, or similar bases, form soaps, and when combined with glycerine 

 form fats. 



Other series of hydrocarbons. The first series of paraffins consists of 

 saturated hydrocarbons ; many other series exist, however, in which the 

 C is unsaturated. Their general forrnulse are as follows : C n H 2i ; 

 CH ln _,; C.H, n _,; CH 2 ,,_,, and so on. 



From each series of hydrocarbons, the corresponding alcohols, acids, 

 aldehydes, and ethers are obtainable. The alcohols derived from series 

 of ethene, C 2 H 4 , are called glycols. But in glycols there are two OH 

 united to the radicle instead of one these are therefore called diatomic 

 alcohols; and similarly acids, of two kinds, may be obtained, by the sub- 



