12 UTILIZATION OF MINUTE LIFE. 



with the hands. These thick threads are used 

 to attach hooks to fishing-lines for large fish. 



Eoard 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 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 lombic 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 



