93 



floating on embryonic lissiie juice. Once a week or so, 

 the fluid, containing Ihe catabolic substances was aspiraled 

 by means of a pipe lie and replaced with a new fresh 

 fluid containing the food materials. None of the jnethods 

 have had any practical applications so far. 



Carrel '"^) solved the problem by conslructing con- 

 tainers and instruments for the special manijniialicjn of 

 the cultures. The principle is, that the culture medium 

 is composed of two parts, solid and fluid; the soliti medium 

 is continually bathed by the fluid medium, which is changed 

 as often it is necessary. 



The containers are flat, round flasks with a 3 cm. long] 

 and 1 cm. wide oblicjue necks through whicli the media 

 may be introduced and removed. The neck is closed with 

 absorbent cotton and a rubber cap. Five types of flasks have 

 been constructed so far. One type has an opening (3 cm. 

 in diameter) at the top, and is used for the cultivation 

 of tissues which cannot be handled conveniently througli 

 the neck of the flask. Tlie opening is closed by a disc 

 of glass or mica. xVnother type has two necks opposite 

 each other to use when bimanual operation is necessary. 

 Another type has a bottom opening closed by a thin mica 

 plate and a top opening. This type is used when the culture 

 has to be examined by the high power microscope during 

 the cultivation. The culture can be removed by the mica 

 plate at the bottom, fixed in formaldehyde, stained and 

 studied under high magnification. 



The culture medium is composed of two parts, solid 

 and fluid. The solid medium is obtained by the plasma clot 

 or fibrinogen, and the fluid medium consists of thin solutions 

 containing the food material. 



The plasma is introduced first (0,5 cc. generally) and 

 allowed to moisten the whole bottom. Then 1,5 cc. of 

 Tyrode solution containing 5 per cent tissue juice, is 

 introducec: and mixed with the plasma. Before the coagula- 

 tion takes place, the fragments of tissues are introduced 



