428 STATE BOARD OF AGRICULTURE. 



1. The nature of the .substance or agglutinogen introduced into the 

 body, 



2. The amount of agglutinogen introduced. 



3. The number of injections and the length of time required to in- 

 troduce the total amount of agglutinogen, 



4. The method of introducing the agglutinogen. 



5. Idiosyncrasy or individual variation in the body receiving the 

 agglutinogen. 



There may be many other influencing factors. The agglutination 

 titer of any sample of blood serum depends to a great extent upon the 

 time it is drawTi relative to the time of treatment of the animal. Other 

 factors influence the agglutinative power of a sample of serum after 

 it is drawn, such as age, temperature and light. These can be easily 

 controlled. 



Of the factors above enumerated which influence the production of 

 agglutinins in the body the first four are subject to control, the individual 

 variation in animals only, being beyond our control. As an illustra- 

 tion of this last point we may say that if we take two pigs of the 

 same sex and litter and as nearly alike as conceivable and subject these 

 pigs to identical treatment in so far as factors 1, 2, 3, and 4 are con- 

 cerned, we may not get identical results when we test samples of their 

 blood for agglutinative power. 



The 19 pigs furnishing the basis of the work outlined in Tables IV 

 to XXII varied greatly in weight, breeding and other characteristics. We 

 could not expect them to respond identically to identical treatment 

 even were there no question of idiosyncrasy. As a matter of fact, the 

 treatment of these pigs has been variable both as regards factors, 1, 2, 

 3 and 4 (considered above) and as regards withdrawal of blood for 

 agglutination tests or other purposes. A comparison of the results 

 secured from a studv of Tables IV to XXIII is, therefore, verv diffi- 

 cult. 



There is a considerable variation in the maximum dilutions at which 

 agglutination occurred. 



Of the 19 cases studied, 



1 or 5.26 per cent gave a maximum reaction at 1 — 2,000. 

 7 or 36.85 per cent gave a maximum reaction at 1 — 4,000. 



1 or 5.26 per cent gave a maximum reaction at 1 — 8,000. 



2 or 10.52 per cent gave a maximum reaction at 1 — 12,500. 

 1 or 5.26 per cent 'gave a maximum reaction at 1 — 25,000. 

 7 or 36.85 per cent gave a reaction at 1 — 50,000. 



It is apparent that a little less than half of the maximum reactions 

 are at one extreme, 200 to 4,000; and a little less than half at the 

 other extreme, 25,000 to 50,000, with a few cases between these ex- 

 tremes. 



A study of one case will illustrate what might be called a typical 

 response to several influencing factors, such as increasing the total 

 of vims injected and repeated bleedings. 



Serum hog 145 (Table XIII) wt. 56 lbs.. July 17. 1909, received 30 

 CO, mixed serum, 30, and 1 cc. virus 107. The weight increased to 150 

 lbs. during the following treatment: 



