DAIRYING. 131 



change in form, is not known. The Ufe history of the bacillus 

 is therefore an urgent problem requiring solution, and for that 

 reason the Institute has been for some time, and is at present, 

 engaged upon it. One practical fact, however, emerges from 

 what has already been discovered ; namely, that a farmer cannot 

 assume that he has got rid of tuberculosis when he has drafted 

 affected cows out of his herd. All the cow buildings should be 

 thoroughly disinfected and finally limewashed. 



A Test for Abnormal Milks. — This account of recent investiga- 

 tions on the subject of clean milk may be concluded by reference 

 to some work on a method suggested by American research workers 

 for distinguishing between normal and abnormal milks. The 

 method consists in adding i drop of a solution of brom-cresol 

 purple to 3 drops of milk in a sterilised tube. With ordinary 

 milk a pale blue colour results. Acid milk gives a yellow colour ; 

 alkaline milk gives a violet colour ; and the degree of intensity 

 of the colour is some measure of the degree of acidity (or alka- 

 linity) of the milk. If a cow's udder is diseased, or if disease 

 organisms have entered the udder through the teat, the milk 

 from that udder will usually be either acid or alkaline, and a 

 small quantity of it may affect the whole bulk of milk produced 

 from the dair}^ herd and render it unsaleable. Diseases of the 

 udder are referred to at some length in the chapter on Animal 

 Diseases (see page 138), and as the brom-cresol test is being 

 examined at the Royal Veterinary College, as described in the 

 chapter, it is unnecessary to refer to it here in further detail, 

 beyond sajang that the Reading Research Institute has been 

 investigating the possibility of producing from it a simple test 

 which would be more within the range of the farmer. The liquid 

 test requires the use of a sterilised test tube, and this is a practical 

 difficulty on the farm. Brom-cresol papers have therefore been 

 made, consisting of absorbent paper soaked with the liquid and 

 dried, and work is in progress to see whether by the use of these 

 papers a farmer will be able to detect abnormal milk from any 

 cow by the simple process of soaking the paper in the milk and 

 observing the colour produced. 



Milk Products. 

 Cheese. — Milk which is not consumed whole is usually made 

 into butter or cheese. About butter-making we know a good 

 deal ; the standard reached in the farm dairy is often very high. 

 Cheese-making, on the other hand, is a subject on which there is 

 very insufficient information, and a great deal of the cheese on 

 the market to-day is a low-grade product, which, however, finds 



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