74 THE MICROSCOPE. May., 



fried Ehrenberg, mit ^ '^ '^' Tafeln, Berlin, 1875. 



It must be imported, but can be obtained tlirougli 

 Messrs. B. Westerman & Co., 812 Broadway, N. Y. The 

 cost will be from five to eight dollars. 



The Character of Agar-agar, and The Bacillariaceae 

 Found in Connection with it. 



By ARTHUR M. EDWARDS, M. D. 



NEWARK, N. J. 



Agar-agar or Bengal Isinglass is a vegetable product 

 obtained in China from sea weeds : Etidcemna spinosmn^ 

 sphcerococcus, licheneides, spinosus, and tenax. These 

 Algas are bleached by the sun and put up in packages. 

 They are almost colorless and look like and are vege- 

 table gelatine. It is used as a medium for the cultiva- 

 tion of Bacteria and is purer than animal gelatine. It 

 dissolves more easily in water also. It comes into 

 commerce in transparent colorless strips, almost com- 

 pletely soluble in water and makes a large quantity of 

 thick, tasteless, and colorless jelly. As dilute sulphuric 

 acid dissolves it, forming galactose, which is character- 

 ised by its conversion" into galactonic acid by oxide of 

 silver, it is readily cleaned. Nitric acid dissolves it also. 

 The siliceous Bacillariaceae are then seen very plainly. 

 It does not require boiling in other acids or Bichromate 

 of Potassa but Hydrochloric acid and Bichromate of 

 Potassa are desirable to thoroughly clean it. Washing 

 with water and weak ammonia afterwards when we 

 have the siliceous shells of Arachnoidiscus ehrenbergii 

 clear and briliant. In this way we can get this Bacilla- 

 rian from the China sea readily. I have also made use 

 of this process on Agar-agar sent to me by Mr. Priest 

 from Japan. It is called birds' nests in China because 

 the sea birds use it in making their nests and it is used 



