QUESTION^ 493 



investigated was remarkably uniform, while in a considerable number 

 of cases the results varied greatly. The more uniform results were 

 found in cows with no previous history of udder trouble of any kind. 

 Some cows of this kind, however, also showed great variations in 

 the count. Eighteen animals in a perfectly healthy group showed 

 in 537 tests a leukocyte contents of 500,000 or less in 90 per cent, of 

 the cases; however, in 16 tests in this group over 1,000,000 were 

 found. The authors state that it is apparent from their studies that 

 the leukocyte content of normal milk drawn from apparently normal 

 animals is quite often so high that the milk would be classed as 

 coming from diseased animals when judged by the standards that have 

 heretofore been proposed and that therefore complete reliance cannot 

 be placed upon quantitative leukocyte standards alone. Stone and 

 Sprague made 1167 leukocyte counts in two perfectly healthy cows 

 during a period of about ten months, examining each day both the 

 morning and the evening milk. These counts varied from 2,110,000 

 to 10,000. The highest counts of over 2,000,000 occurred the first 

 two days of lactation, but counts between 100,000 and 500,000 were 

 found in 29 per cent, of all counts. The authors state that their con- 

 fidence in an arbitrary numerical leukocyte standard as the reliable 

 criterion of the sanitary fitness of milk has been very much shaken; 

 but they believe that the physiological average is considerably below 

 500,000. Ward, likewise, is of the opinion that a leukocyte count alone 

 does not generally furnish data from which the presence or absence 

 of inflammatory conditions in the udder can be diagnosticated. 



QUESTIONS. 



1. Discuss the presence of tubercle bacilli in milk. In what form of tuber- 

 culosis are they most frequently found in milk? 



2. In what percentage of market milk have they been found? 



3. Is every milk containing tubercle bacilli likely to produce tuberculosis 

 in man? 



4. What is the procedure for discovery whether samples of milk contain live 

 virulent tubercle bacilli ? 



5. Give in detail the method of searching for tubercle bacilli in butter. 



6. How can typhoid bacilli get into milk? 



7. What is known about milkborne typhoid epidemics? 



8. How may the diphtheria bacillus get into milk? 



9. What is known about milkborne scarlet fever epidemics? 



10. What other cattle diseases, aside from tuberculosis, may be transmitted 

 through milk? 



11. What are the most common bacteria in mastitis in cows? 



12. Discuss the number and significance of leukocytes in milk? 



13. What is a colostrum corpuscle? Where does it come from? 



14. What is Stokes' method of estimating leukocytes in cow's milk? 



15. What is Stewart's method? 



16. What is Trommsdorf's method? 



17. Which is the most accurate method of estimating leukocytes in milk? 

 Describe its details. 



18. Describe a Thoma-Zeiss blood-corpuscle counting chamber. 



19. Describe the method of calculating the result of a leukocytic count in milk. 



20. What effect has heating the milk upon the leukocyte count, and why? 



21. Describe the variability of the leukocyte count in the milk of normal cows. 



