196 



SCIENCE PROGRESS 



The nature of the differences leads us to a real picture of 

 the underlying differences between the kinds of protoplasm. 

 The tide of thought of the older observers was fettered by the 

 act that all proteids have about the same atomic composition. 

 The biologist of to-day owes his emancipation to the chemical 

 discovery that the properties of a complex substance are defined 

 not so much by the kind of atoms or number of atoms of which 

 it is built, as by the arrangement of those atoms in space. 



Here is a simpleand startling case. The molecules of two 

 chemical substances, benzonitrile and phenylisocyanide, are 

 composed of seven atoms of carbon, five of hydrogen, and one of 



nitrogen 



C 

 1 1 1 1 



N 

 11 

 c 



H 



H 



H-C 



H-C 



C-H 



C-H 



SEN26NITRIUE 



c 



H 



PH£N\ LI SO CYAN IO E 



There is a small difference in the arrangement of these atoms 

 which is illustrated by the diagram. Now, what are the proper- 

 ties of these two substances ? They are as unlike as possible. 

 The first is a harmless fluid with an aromatic smell of bitter 

 almonds. The second is very poisonous and offensive. 



A vivid impression in regard to the odour of the iso- 

 cyanides may be produced by the following experiment. In a 

 test-tube bring together a little chloroform, aniline, and alcoholic 

 potash. The reaction takes place at once. // is better to perform 

 the experiment out of doors and in sitch a place that the tube with its 

 contents can be thrown away without molesting any one. 



In the building of a complex molecule one has atoms gathered 

 together to form groups, these to form larger groups, and the 



