IMMUNITY 27 



only at low temperatures — probably in the capillaries 

 during exposure to the cold — and hemolysis sub- 

 sequently resulted in the blood stream by the action 

 of complement. In this way probably azoturia is 

 caused ; the tissues of the body, which have become 

 over-rich in proteid material by high feeding and rest 

 of the animal, may during work liberate a proteolytic 

 toxin, formed by the breaking up of the protein 

 elements. These toxins probably have a hemolytic 

 action on the red cells of the body, the hemoglobin 

 being excreted through the urine. 



Tests for Differentiation of the Various Organisms 



causing Disease. 



By reviewing the preceding sections we observe that 

 various phenomena are established in the serum of an 

 animal suffering, and which has suffered, from a disease. 

 By a practical application of each phenomenon, we 

 have various means for determining the nature of the 

 micro-organisms which produce the disease. 



Ag-g-lutination Test.— This is extensively used in 

 human medicine in making an early diagnosis of 

 typhoid fever, and in veterinary medicine in diagnos- 

 ing animals infected with contagious abortion. If we 

 know the dilution at which organisms are agglutinised 

 by a serum containing the specific immune bodies for 

 the particular bacteria, this test has a wide range of 

 application. 



Precipitin Test. — This is used chiefly in human 



