358 VETEEINARY STATE BOARD 



ide, and then one drop of a 2 per cent, solution of hydrogen dioxide. 

 Unheated milk gives a blue color when thus treated, but milk heated 

 to 170° F. gives no color. 



Arnold's guaiac test: Add, drop by drop, a little tincture of 

 guaiae to a small amount of milk in a test-tube. If the milk has not 

 been heated to 80° G. (170° F.), a blue zone is formed between the 

 two fluids ; heated milk gives no reaction, but remains white. 



Give a test for formaldehyde in milk. 



Place about 20 c.c. of milk in a small glass vessel, dilute with 

 an equal volume of water, and add, by pouring slowly down the 

 inside of the vessel, a small amount of 90 per cent, commercial sul- 

 phuric acid. If formaldehyde is present, a purple or bluish zone will 

 appear at the junction of the acid and milk. If no formaldehyde is 

 present, a faint, slightly greenish ring forms. This test will detect 

 formaldehyde even if present in as small proportion as 1 in 200,000. 



Name the common preservatives used in milk. 



Boric acid, salicylic acid, formalin, benzoic acid, potassium 

 bichromate. 



Give the cause for: (a) ropy milk, (b) bitter milk, (c) blue milk, (d) 

 red milk, (e) suppression of the milk, (f) pus in the milk. 



(a) Inflammation of the udder may cause ropy milk, but in the 

 majority of cases it is due to B. lactus viscosus. 



(b) Eating of certain foods by cows (lupines, ragweed, cab- 

 bages, Swedish turnips) ; it occurs in old milk due to growth of 

 germs. 



(c) Bacillus cyanogenus. 



(d) A mixture of blood: B. prodigiosus. Rarely due to eating 

 of pigmented plants. 



(e) Mastitis, severe febrile diseases, certain drugs such as bella- 

 donna, idodine, camphor, alum, etc. 



(f) Mastitis. (A small number of leucocytes is often found in 

 milk from apparently healthy cows.) Prolonged retention of milk 

 in the udder gives rise to an increased leucocyte content. 



Describe briefly: (a) sanitary farm, (b) sanitary barn, (c) sanitary 

 milk-house. 



(a) A sanitary farm is one that is located sufficiently high to 

 have good drainage, and that is free from germs of infectious 

 diseases. 



(b) A sanitary barn is one provided with good drainage, venti- 

 lation, and light, and pure water supply; it has the necessary 



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