PRECIPITINS 147 



an animal with horse serum, or, if we prefer, with 

 an extract of horse-flesh. The serum derived from 

 this animal will then produce a precipitate in the 

 aqueous extract of the meat if this be horse-flesh, 

 but not if it be beef. Animals treated with dog 

 serum yield a serum which precipitates an aqueous 

 extract of dog-flesh, etc. The method of examina- 

 tion consists in scraping the meat and extracting it 

 with water or normal salt solution. It takes a long 

 time to extract the meat in some cases. An extract 

 is suitable for testing when it foams on being shaken. 

 If the extract is very cloudy it should be cleared by 

 filtration through a Berkfeld filter. In testing, add 

 ten to fifteen drops of antiserum to 3 cc. of the 

 saline meat extract. 



Neisser and Sachs l have recently described a 

 procedure for the forensic diagnosis of blood stains. 

 The principle of this is the same as the Wassermann 

 reaction. If human blood serum is mixed with a 

 specific human precipitin serum derived from rab- 

 bits, it will be found that the mixture binds com- 

 plement. Haemolysin subsequently added is unable 

 to dissolve its specific red blood cells, owing to this 

 locking up of the complement. Only the serum of 

 monkeys has a similar effect. The amount required 

 is extremely minute, .0001 to .00001, human blood 

 or monkey blood sufficing. Extracts of human blood 

 stains will also produce the desired effect. The authors 

 1 Neisser and Sachs, Berliner klin. Wochenschrift, 1905. 



