Chemical Simulation of Organisms for Class Use 



Illo Hein 



To enliven the student's interest and arouse his curiosity in 

 plant and animal form development excellent opportunities are 

 given the teacher in the hitherto neglected chemical imitations 

 of organisms. Many beautiful and suggestively similar imita- 

 tions of leaves, roots, stems, fern fronds, fungi, wing patterns of 

 butterflies, bird feathers, a variety of sea life, algae, shells, corals 

 "fairy rings," cell shapes, division figures, and countless other 

 organic forms and patterns can be easily made with a little ex- 

 perience in the appropriate mixing of certain chemicals. Such 

 imitations as have been made by Liesegang (1911), Ktister 

 (1913), Leduc (1912), and Gebhardt (1912) are stimulating and 

 suggestive not only to the investigator but also to the students 

 in elementary biology for whom they should be as instructive as 

 entertaining. 



The student can with simple apparatus and a few chemicals 

 perform the experiments himself or they may be made by the 

 teacher as demonstrations. The student can see before his eyes 

 the production of forms and patterns in inert substances by 

 some of the same processes which take place in and control the 

 growth of organisms. 



Just a few of the possible demonstrations are given below as 

 suggestive of what can be done. Many other striking imitations 

 can be devised by an imaginative teacher either by modifying 

 or elaborating the directions given or by using other chemical 

 combinations many of which may be found in the appended 

 literature list. The materials and apparatus are inexpensive and 

 can be employed with little expenditure of time. 



Very beautiful imitations of fern fronds which are striking in 

 their similarity may be made with certain crystalline precipi- 

 tates in colloid solutions. A small plate of window glass, cleaned 

 photographic plates, or lantern slide covers are very satisfac- 

 tory. The plate is coated with a thin ten percent solution of 

 gelatine containing five cc. each of saturated solutions of am- 

 monium chloride and sodium chloride. The salts will crystallize 

 out over night in various patterns many of which are similar in 

 appearance to the outline of the fronds of selaginallas and ferns. 

 (Figs. 3 and 5). 



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