CONTENTS 



FAGB 



HISTORICAL 17 



THE PHYSIOLOGY OF LACTATION 32 



Definition of milk, 32 Location of mammary glands, 33 Develop- 

 ment of the mammary gland, 34 Formation of the secretion, 34 

 Relation of colostrum to secretion, 36 Theories of lactation, 37 

 The secretion of milk, 40 Duration of the lactation period, 43 

 The total quantity of milk produced during a lactation .period, 44 

 The cow's udder, 45 The quantity and quality of milk produced by 

 cows, 49 Bibliography, 50. 



THE PHYSICAL PROPERTIES OF MILK 51 



Microscopic study of milk, 51 Creaming, 52 Cellular elements in 

 milk, 57 The nature of the fat globules, 60 Colostrum, 62 Proper- 

 ties of normal milk, 63 Odor and taste, 64 Viscosity and cohesion, 

 64 Specific gravity, 65 Freezing-point, 67 Electric conductivity, 

 67 Refractivity, 67 Specific heat, 68 Bibliography, 69. 



GENERAL CHEMISTRY OF MILK 70 



Composition of milk, 70 Composition of colostrum, cream, skimmed 

 millc, whey, buttermilk, 73 The physiologic origin of milk constit- 

 uents, 75 Origin of casein, lactalbumin, and globulin, 75 Origin 

 of butter-fat, 76 Origin of milk-sugar, 78 Origin of mineral con- 

 stituents, 78 The chemistry of butter-fat, 78 The decomposition 

 of butter-fat, 81 The chemistry of casein, 82 Properties of bovine 

 casein, 88 Rennet coagulation, 90 Conditions governing rennet 

 action, 93 Lactalbumin, 97 Lactoglobulin, 9& Mucoid protein 

 or lactomucin, 98 Other proteins in milk, 98 Lecithir and cephalin, 

 99 Nitrogen-containing extractives, 99 Milk-sugar, 99 The min- 

 eral constituents of milk, 101 Gases in milk, 102 The reaction of 

 milk, 104 Variability in the composition of milk, 105 Difference 

 in composition due to breed, 106 Difference due to individuality, 110 

 Variation in composition during the lactation period, 114 Influ- 

 ence of food on milk, 123 Influence of weather and temperature on 

 milk, 126 Exercise and nervous influences, 127 Influence due to 

 the skill of the milker, 127 Changes in composition of milk, 128 

 Spontaneous changes, 128 Freezing of milk, 128 Influence of heat 

 on milk, 131 Centrifugation of milk, 132 Dilution of milk, 133 

 Dialysis, 133 Electricity, 133 Bibliography, 134. 



THE PHYSICAL AND CHEMICAL EXAMINATION OP MILK 136 



Sampling, 136 Composite samples, 140 The specific gravity, 141 

 The determination of fat, 147 Ether extraction of fat, 147 

 Refractometer method, 148 The Babcock method, 155 Modifica- 

 tions of the Babcock test, 164 Testing cream by the Babcock method, 

 167 Testing skimmed milk, buttermilk, and whey by the Babcock 

 method, 173 Determination of total solids and plasma solids, 175 



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