PROBLEM I. The Co?npos'ition of Livmg Things 



109 



Fig. 143 Dr. Walter S. 



Ritchie of the University of 

 Massachusetts is study i7ig 

 some of the coijipoiinds 

 found in protoplasDi. (uni- 

 versity OF MASSACHUSETTS) 



phosphorus (P), iron (Fe), potassium 

 (K), and magnesium (Mg). Many other 

 elements have been found in some pro- 

 toplasm and traces of certain others may 

 be present in all protoplasm. 



Compounds in protoplasm. The ele- 

 ments in protoplasm are usually not 

 found as elements but are combined 

 chemically to form substances known 

 as compojijjds. Compounds are chem- 

 ical combinations of elements. When 

 elements combine chemically they form 

 a new substance which is different from 

 the elements that make it up. podium. 

 f or ^ exam ple, is a metal that would b urn 

 your skin if you touched it, and chlorine 



ox 



ggmbj ii e^ ch e m icaJIyL f orm- 

 ing water, a compound \vhi ch has very 

 different properties from eithe r hydro-_ 

 gen 'or oxygen. And so with all other 

 elements; when they unitg_jdiemically 



they loG G i h o ir clu racteristics and some- 



thirfg new appea?S. Yuui"~feaclier can 

 perform ExercIISE KO so that you can see 

 for yourself how the characteristics of 

 elements disappear when they combine 

 and form a compound. Compounds 

 themselves combine chemically with each 

 other and when they do they form new 

 compounds with definite characteristics. 

 There are many different compounds 

 found in protoplasm but there are only 

 a few that are always present. The most 



is a poisonous gas. i hese two substances 

 rnmhvmpT^^Hiiiw-ijllyj^na]^ a r-n^^ ppun^- — abundant of these is water; it forms a 

 thatis called sodium chlo ride or ordinary la rge part of all protoplasm. Other corn- 

 table salt. The two gases, hydrogen and pounds are salts like sodium chloride. 



