Hoyberg's Test. 215 



lactic acid. In spite of this, the degrees of acidity of Henkel- 

 Soxhlet cannot be computed into the degrees of acidity of Pfeifer 

 because through dilution with water the solution of slightly soluble 

 phosphates decreases the degrees of acidity obtained, and, there- 

 fore, the degrees of acidity of Thorner and Pfeifer show lower 

 values than those of Henkel-Soxhlet. 



Milk from individual cows often have greatly decreased or 

 increased degrees of acidity. The decreased, or, more rarely, in- 

 creased degree of acidity of a single sample creates the suspicion 

 that the cow is suffering from udder disease. High acidity of all 

 four quarters is present with colostrum and in milk of fresh cows. 

 The milk from cows at later periods of lactation is frequently 

 alkaline and has a lower degree of acidity. 



Dropped on litmus paper, market milk shows an amphoteric 

 reaction. Alkaline reactions of single samples must be judged 

 the same as low degrees of acidity. If market milk shows an alka- 

 line reaction, an alkali may have been added for preservation. 

 The reaction of market milk is acid to rosolic acid. On the addi- 

 tion of alkali to milk, the milk, upon adding rosolic acid-alcohol, 

 turns rose red. With fresh single samples of milk the red color 

 after the addition of rosolic acid-alcohol is an indication of the 

 presence of inflammation of the udder; cows in the late periods 

 of lactation may also show red coloring of the milk. 



To lacmoid the milk is alkaline, and also to dimethyl orange. 

 The so-called Hoyberg test to determine "fibrin and pus" in 

 samples of milk from individual cows is based on the difference 

 in the reaction of the milk. 



The test is conducted so that 5 c. c. milk (individual cows or 

 quarters) are mixed with 5.5 c. c. solution of rosolic acid, which 

 is prepared from 0.45 c. c. of a 1% solution 5 c. c. plus alcohol. 



A positive reaction to the test creates suspicion while a nega- 

 tive result does not exclude it. 



As the reaction of milk from diseased quarters frequently is 

 perfectly normal or acid, the test does not compare with the 

 Trommsdorff test, and especially the microscopical examination. 

 Besides, it is very difficult to distinguish the fine differences in the 

 color shades. 



The determination of the alkalinity of milk with -fa normal 

 acid has so far not been adopted in practice. 



The dirt content of milk should not be weighed, as recom- 

 mended by Renk, since the amount of visible foreign material 

 should not determine the disposition, but rather its quality 

 should be considered. Besides, much dirt is dissolved in the milk, 

 which neither can be determined through filtration nor through 

 weighing the filters. The amount of dirt is estimated in degrees, 

 through the sedimentation method or through filtration, and the 

 quality is thus determined; as a rule it represents remnants of 

 feed, feed dust, portions of litter, manure of cows, cow hairs, etc. 



