THE PRECIPITINS 237 



complement. According to Neisser and Sachs, however, this 

 power is destroyed if the serum solution is boiled, but is unaltered 

 in the case of non-specific substances. Another serious objection 

 is that a similar deviation may be brought about by means of 

 sweat, so that if the reaction were obtained in a stain on body- 

 linen it would be of little value. 



The precipitin reaction has also been used for determining the 

 nature of meat (whether fresh, as in the case of beef suspected to 

 be horse-flesh, or prepared, as in sausages, etc.). The serum is 

 prepared by injecting meat-juice or an (unheated) watery extract 

 of the meat, and the test is carried out on lines similar to those 

 described above. It has also been employed to determine the 

 nature of bones, i.e., whether they are human or otherwise. 



