12 UTILIZATION OP MINUTE LIFE. 



with the hands. These thick threads are used 

 to attach hooks to fishing-lines for large fish. 



Board and Mulder have endeavoured to ascer- 

 tain the chemical nature of silk. The latter chemist 

 has recognized in it a peculiar animal matter, which 

 he terms fibroin, or pure silk-fibre. When the 

 liquid silk taken from the body of the grub is 

 placed' in acidulated water, it coagulates into a 

 mass of minute white filaments. When secreted 

 by the silkworm a portion of this liquid solidifies 

 and forms a simple thread of silk, which, in con- 

 tracting, expels from its interior a liquid that 

 solidifies on the surface of the thread, forming a 

 sort of varnish. It is the latter which gives to 

 certain silks their natural yellow colour. 



The analysis of Mulder shows that N the liquid 

 secretion of silkworms contains about half its weight 

 of pure silk-fibre (fibroin), the remaining portion 

 consists of albumen, two kinds of grease, a species 

 of gelatine, and a slight quantity of a red colour- 

 ing matter. The spider's web shows a perfectly 

 similar composition. 



Mulder has shown that by distilling silk with 

 diluted sulphuric acid, a peculiar product is obtained 

 called bombic acid. It may also be obtained by 

 boiling raw silk with water, and evaporating with 

 precaution. This bombic acid is an extremely in- 

 teresting product, first noticed by Chaussier. It is 



