172 BACTEEIOLOGICAL METHODS 



trifugalizing or by filtration, but the titer must again be tested. 

 Preservatives such as carbolic acid, etc., should not be added to 

 the sera. Sterile sera are obtained by filtration through Berke- 

 feld filters. Drying of the sera on filter paper is the best method 

 known for preserving them {Jacohsthal und v. Elsler). 



2. The Preparation of the Meat Extract. — To make the bio- 

 logic test for horse or deer meat, remove from the deeper parts 

 of the specimen, by means of a flamed or boiled knife and through 

 a fresh opening, a piece of muscle of about 30 grams weight. 

 It should contain as little fat as possible. On a sterilized tile 

 (best covered with unused writing paper) chop the meat carefully. 

 The finely minced meat is placed in a sterilized 100 cc. Erlenmeyer 

 flask and spread out with a sterile glass rod and covered with 

 50 cc. sterile saline solution. Salted meat is washed for 10 

 min. in a large flask with distilled water, renewing the water 

 several times, without shaking the flask. 



The mixture of saline and meat is kept for about 6 hr. 

 at room temperature, or over night in the refrigerator. To 

 obtain a clear solution the flask should not be shaken. 



Since the presence of fat interferes with the reaction, it is 

 advisable to remove it by means of ether and chloroform. To 

 make the extraction, take 75-100 grams of the minced meat, 

 place in a large Erlenmeyer flask and cover with equal parts of 

 ether and chloroform. After 24 hr. the ether and chloroform are 

 poured off, the meat is washed once or twice with sahne solution 

 and then extracted, as stated above. 



To determine whether a sufficient quantity of protein sub- 

 stances has passed into solution, place 2 cc. of the extract in a 

 test-tube and shake vigorously. If a fine foam develops and 

 persists for some time, the extraction may be said to be sufficiently 

 complete. The protein solution must be perfectly clear and must 

 therefore be filtered. With extracts from fresh meat this is 

 usually accomphshed by filtering through a firm filter paper 

 previously moistened with saline solution. If it is not crystal 



