PRINCIPLES OF VETERINARY SURGERY 173 



ten c.c, then 1-5 c.c, or about three drops, would he the 

 amount. The next step is. to place the test-tube in the in- 

 cubator at 2,7° C or in room temperature for eighteen hours : 

 then examine : If the test is positive, i. e., if the animal is 

 infected with bacillus dysenteric, the bouillon has lost its 

 opacity: the bacteria will have agglutinated, and will form 

 clumps at the sides and bottom of the test-tube which are 

 visible to the naked eye. 



Care must be taken to dilute the blood, as normal serum 

 undiluted will also cause agglutination. The amount of 

 dilution differs with different species. With some bacteria 

 the reaction is positive with a dilution of one-thousand. 



The agglutination not only takes place with bacteria, 

 but also with red blood corpuscles and other animal cells. 

 Pathologists are beginning to explain thrombosis and em- 

 bolism by this phenomenon. 



PRECIPITINS: — The precipitin test is being- used in 

 biology to classify the different species of animals. Its 

 practical application in veterinary science lies in the differ- 

 entiation of bloods, meats, and albumins. In the chapter 

 on Hsematology, the test is applied to the blood, It may 

 become necessary sometime to decide whether a piece of 

 meat is that of beef, of a horse, or of some other animal. 

 Neither anatomical, nor histological, nor chemical examina- 

 tion can decide. It is necessary to resort to the precipitin 

 test. 



If we wish to determine whether a given sample of 

 meat is beef or not, we inject a little ox serum into a rabbit, 

 (about 5 to 10 c.c.) twice a week for a month. Then take 

 some of the rabbit's serum and place in a test-tube; make an 

 aqueous extract of the sample of meat and add about i c. c. 

 of it to the ox-serum. Put in the incubator for a few hours. 

 If the meat in question be beef, we shall get a precipitate, 

 a marked, floccnlent, clouding. But, if the meat be from 



