ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 343 



alkali. The fluid is then distributed into stoppered bottles and chloro- 

 formed and treated as above. 



Sterilization of Blood.—The blood, collected at the slaughter-house, 

 is defibrinated by stirring with a large wooden stick wrapped in gauze, 

 the whole being previously sterilized. In order to sterilize the blood by 

 the heat-chloroform method it is necessary to lake it before adding the 

 chloroform. For this purpose an equal part of distilled water is 

 added to the blood, and the mixture distributed as in the case of serum, 

 9'5 p.c. chloroform is then added, and the bottles are well shaken. The 

 bottles are placed in the air incubator at 37° 0. and shaken constantly. 

 After twenty-four hours a sample is taken to test for sterility, and 

 pending the result the bottles are not returned to the incubator, because 

 the longer blood is heated the darker the colour becomes. Twenty-four 

 hours is invariably long enough to ensure sterility. If subsequently 

 mixed with agar care must be taken that it is not heated above 55° C, 

 and for as short a time as possible. 



Method of Preparing Media with Sterile Albuminous Fluids. — 

 1. Ascitic agar — ordinary lemco- (or meat-) pepton agar is prepared 

 containing 2^-3 p.c. agar. It is measured into 200 c.cm. flasks in 

 •quantities of 150 c.cm. and autoclaved. When required for use a flask 

 of agar is melted and treated in one of two ways : (a) It is poured into 

 a sterile distributer, maintained in a water bath at 59" C, and a flask of 

 ascitic fluid (50 c.cm.) is added. The contents are mixed and then tubed 

 through a hooded pipette, {b) The flask of ascitic fluid may be poured 

 directly into the melted agar in its flask and mixed, and then rapidly 

 poured into Petri dishes or tubes. The agar should be mixed with the 

 ascitic fluid at a temperature as low as possible. This medium is 

 admirable for primary throat cultures of the meningococcus. 2. Serum 

 agar. This medium is prepared in exactly the same way as ascitic 

 agar, using serum. Meningococci sometimes fail to grow on this 

 medium. 3. Blood agar. An excellent transparent blood agar may be 

 prepared by adding 25 p.c. of sterile laked blood to2|-3 p.c. agar. The 

 finished medium thus contains 12-5 p.c. of blood. 4. Blood serum agar. 

 This is the medium the author uses for all routine work with the 

 meningococcus, except the primary cultures from the throat. It 

 contains a small but sufficient quantity of laked blood. He uses one 

 part of blood in 400 of medium, 1 c.cm. of the laked blood (diluted 

 1 in 2) being added to each 50 c.cm. flask of the serum, or the blood may 

 be added in bulk to the bottle of serum before this is distributed into 

 flasks. In order to reduce the colour, neither lemco nor meat is used 

 in the preparation of the agar ; merely salt solution and pepton 

 (Morson's). The growth of the meningococcus on this medium is 

 profuse. Other delicate pathogenic organisms, such as the pueumococcus 

 and streptococci, also develop abnormally large colonies upon it. 



War Media— Snail Bouillon.* — P. RemHnger states that various 

 varieties of snails (" abundant in certain gardens to the point of consti- 

 tuting a regular plague " !) can furnish a nutrient broth capable of 

 being used for most bacteriological purposes. It is prepared in the 



* C.R. Sdc. Biol. Paris, Isxx. (1917) pp. 1109-10. 



