"Ci^'Jarrisra'] of Milh under certain Conditions. 37 



owing to this state of the mUk, To prevent these evil consequences, 

 M. V. Esshng recommends the milk to be drunk as soon as possible 

 after extraction, and at all events to keep it closely bottled during 

 the interval, so as to keep out the smallest particle of air. More- 

 over, the temperature should be kept as nearly as possible the same 

 as that which the milk had in the teats." 



Having for many years been famihar with the microscopical 

 appearance presented by milk and cream, and not haviug seen the 

 changes as described by M. V. Essling, I was desirous of satisfying 

 myself on this point, more especially as it affected a very important 

 article of food. The composition of ordinary milk, as stated by 

 Fownes, is as follows : — 



Water, 873- 00; butter, 30 30 ; casein, 48 • 20 ; milk sugar, 

 43*90; phosphate of hme, 2' 31 ; phosphate of magnesia, • 42 ; 

 phosphate of iron, • 07 ; chloride of potassium, 1 • 44 ; chloride of 

 sodium, • 24 ; soda in combination with casein, • 42 : total, 

 1000-00. 



Composition of casein in 100 parts : — Carbon, 53 • 83 ; hydrogen, 

 7 • 15 ; nitrogen, 15 • 64 ; oxygen and sulphur, 23 • 37 : total, 100 • 00. 



Composition of albumen in 100 parts : — Carbon, 53 • 5 ; hydi'ogen, 

 7"0; nitrogen, 15-5; oxygen, 22-0; phosphorus, • 4 ; suljDhur, 

 1-6 : total, 100-00. 



Casein and animal albumen are remarkably similar in compo- 

 position; casein differs in not being coagulated by heat, and is 

 precipitated by acetic acid. Certain animal substances cause its 

 coagulation, such as the dried stomach of the calf, known as rennet, 

 used in the manufacture of cheese. 



When a thin film of milk is examined with the microscope, it is 

 found to be a transparent fluid, in which are floating numerous 

 transparent globules of fat ; these are surrounded by a thin pellicle, 

 and when this pellicle is broken mechanicaUy, as by churning, the 

 fat is liberated and forms butter. The fluid part consists of casein, 

 saccharine matter, and salts in solution. The proportion of these 

 organic principles varies in different animals, and also in the same 

 animal when well fed under diflferent conditions. Human milk 

 usually contains a larger proportion of sugar than cow milk, and is 

 coagulated with greater difficulty. It is well known that the secre- 

 tion and quality of milk is influenced by the mental emotions. 

 Milk as obtained in towns is frequently adulterated, and as foreign 

 matter would alter its microscopical characteristics, it was neces- 

 sary to procure pure milk. One of the members of the Literary 

 and Philosophical Society of Manchester, Mr. Kipping, kindly 

 supplied me with a bottle of fresh-drawn milk. The cow had 

 calved about three months previously, and had been fed on grass, 

 bran, and bean flour. This milk was examined soon after I 

 received it, and was found to be very rich in oleaginous globules, 



