May 15, 1891.] 



SCIENCE. 



275 



etc., are not common in the dairy, and they may be kept out of 

 the milk by using sufficient care. Their home is in filth, and they 

 are usually troublesome because of uncleanness. Go to an ordinary 

 cow shed and look at the conditions surrounding the cows. The 

 cows are usually covered with filth, and are practically never 

 clean. They wander at will through the day in swamps, or any 

 muck that they may happen to find, and have every facility for 

 dragging their teats through the mire, or they lie in the mud, and 

 thus insure the fouling of the bag and teats. At night they have 

 no choice except to lie in filth. The farmer goes to the milking 

 in a condition frequently almost as dirty as the cow, and uses 

 vessels which are never thoroughly cleaned. What better chance 

 could there be for filth bacteria to grow? If there are any trouble- 

 some bacteria around, they will be sure to get into the milk in some 

 way, and the wonder is not that milk sometimes undergoes trouble- 

 some fermentations, but that we ever succeed in getting milk fit 

 to drink. These are usually the causes of the troubles that the 

 farmer has with his milk. 



I have in mind now a cheese factory which was at a certain 

 season troubled with a badly-tainted milk, and this finally became 

 so troublesome as to interfere with its business. A man with a 

 pair of bright eyes was set to work to discover the cause of the 

 trouble. He soon succeeded in tracing it to the milk of a single 

 customer. If the milk brought by this man were kept away, the 

 rest remained all right. Examioing into the conditions of this 

 patron's farm, he found that the cows were in the habit of wander- 

 ing through a slimy swamp, and that the material from the swamp 

 would get into their hair and teats, and hence in the milk. This 

 was the sole cause of the trouble, for as soon as the cause was re- 

 moved, the milk was good again. 



I repeat, then, that the abnormal fermentations of milk can be 

 prevented by using sufficient care. The time is coming when the 

 farmer will be ashamed to own that he is troubled with slimy or 

 bitter milk, for it will be regarded as indicating a lack of sufiicient 

 care and cleanliness in the arrangements of his barn. Keep your 

 cow sheds clean, clean the cows themselves, give them clean beds 

 to lie on, wash their teats, sand the floor, let a little of the first 

 milk that runs out of the teat fall to the floor instead of into the 

 milk vessel. If you want to convince yourself of the value of this 

 last procedure, try the experiment of letting the first milk run into 

 a separate vessel, and then see how much sooner it will sour than 

 the rest. The first milk that comes out partly washes the milk 

 duct, and hence contains the bacteria in great numbers. Clean 

 your hands before you milk, and, above all, exercise more care in 

 cleaning the vessels in which you milk. These cannot be suffi- 

 ciently cleaned by a simple short scalding with hot water. Boil 

 them once in a while for a long time on the stove, and you will 

 find the time well spent. 



These, then, are the remedies for all of the unusual fermenta- 

 tions, and every one must apply them for himself. It is impossi- 

 ble to tell beforehand where the trouble lies in your special case. 

 It may be in the condition of the cow, or in the condition of the 

 food, or the milker, or in the dairy itself; but, if you only look 

 carefully for it, you will always find the mischief lies somewhere, 

 and can be avoided by the exercise of sufficient care. 



It is as important to make a careful toilet for the milking shed 

 as for the supper table. Indeed, is it not more so? At the table 

 a little dirt will produce no special trouble, but in the milking 

 yard it may entail much trouble on yourself, and all using your 

 milk in any form. 



All of this will not, however, prevent the ordinary souring of 

 milk. In spite of the greatest care, the bacteria which cause the 

 lactic fermentation will get into the milk, and there is no practical 

 way of avoiding them. Is there, then, any way by which the 

 souring of milk may be prevented ? 



We may first ask if we cannot kill the bacteria after they get 

 into the mUk, for if this can be done, of course the milk will not 

 sour. The simplest suggestion is to find some chemical which will 

 kill them. It is easy enough to find such a chemical. Corrosive 

 sublimate will poison them, and will also poison any one who may 

 subsequently drink the milk. Of com-se such a violent poison 

 will not answer. It is necessary to find something that will poi- 

 son the bacteria and at the same time be harmless to man. One 



of the first substances ever used for this purpose was horse-radish. 

 More than fifty years ago it was stated that horse-radish would 

 prevent milk from souring. But when we drink milk we want it 

 to taste like milk, and not like horse-radish. The poison used for 

 preserving milk must, then, not give a taste of its own to the 

 milk. 



Within the last few years several chemicals have been tried for 

 this purpose with some little success. Those most used are car- 

 bonate of soda, borax, boracic acid, salicylic acid, quick-lime, and 

 some others not so common. In regard to these, we may sum- 

 marize the results of recent experiments briefly as follows: Sali- 

 cylic acid is of the most use in delaying the souring of milk. It 

 can be used in proportions of 1-1000, about a teaspoonful to a gal- 

 lon of milk. Borax comes next in value. It may be used in pro- 

 portions of 3-1000, about Ihree spoonfuls to a gallon. When 

 used in these proportions, the two preservatives mentioned will 

 assist the milk in keeping sweet for a short time longer than if 

 they were not used. None of the others seem to be of any value, 

 or at least of not enough to make it worth while to use them. 

 Most of the preservatives sold in the market to-day are some com- 

 pounds of these chemicals, and it is just as well for the farmer to 

 buy the borax or salicylic acid pure, as to buy the patent mixture, 

 and pay the price of the patent. At best, however, the use of 

 chemicals for preserving milk is very limited, and it is not recom- 

 mended today by any who have made a study of the fermentation 

 of milk. 



The method of milk preservation most commonly in use is that 

 of heat. It is well known that high heat will kill all living things, 

 and, of course, if milk be heated hot enough, the bacteria in it will 

 be destroyed. It is found, however, that a temperature of boiling 

 is not sufficient to kill all of the bacteria in milk. The bacteria in 

 milk are in two diflierent conditions. Some of them are active, 

 perhaps swimming around in the milk, and are always rapidly 

 growing. Others are in a dormant condition, which is known as a 

 condition of spores. The spores correspond in a measure to seeds, 

 and although they are dormant, each one has in itself the power 

 to germinate and produce anew the active form of bacteria. Now 

 it is found, that, while the temperature of boiling will kill all of 

 the active forms, it will not kill the spores. To kill these by heat, 

 the milk must be heated under pressure, since this renders it possi- 

 ble to obtain a higher temperature. A temperature of 230° F. 

 will destroy these spores, and render the milk absolutely without 

 life, absolutely sterile. Such milk will keep indefinitely without 

 souring or undergoing other fermentation. 



Of course it is not an easy matter to heat milk under pressure, 

 and some other method of accomplishing the same purpose is de- 

 sirable. It is found that a long continued boiling at the ordinary 

 pressure of the air will sterilize the milk. It is also found that 

 sterilization may be accomplished by what is called discontinu- 

 ous heating. This is simply heating the milk to a temperature 

 of boiling for a short time on several successive days. If milk be 

 placed in a bottle and boiled a few minutes upon three successive 

 days, it will be sterilized and remain subsequently without bac- 

 teria growth. 



Based upon these facts regarding sterilization, a large number 

 of forms of apparatus have been invented for conveniently accom- 

 plishing the heating. Several sterilizers of milk are on our mar- 

 kets, and still others in Europe. One of the simplest methods of 

 sterilization is within the reach of every one. Place some milk in 

 bottles with long necks and plug the neck with a wad of cotton 

 wool. Then place the bottles in a common steamer, with which 

 almost every house is provided, and steam the milk for an hour. 

 This may not absolutely sterilize the milk, for a very few bacteria 

 in the form of spores may be left alive. But it will so nearly 

 accompHsh the purpose that the milk will keep perfectly sweet for 

 many days, and may be carried on a journey with impunity, pro- 

 vided the cotton plug is not removed. If desirable, a common 

 cork can be put in the bottle on top of the cotton plug, to prevent 

 the spilling of the milk. 



The use of sterilized milk is rapidly becoming common. A few 

 years ago no one ever heard of it, but now, especially in the cities, 

 where it is impossible to get fresh milk, its use is growing x'apidly. 

 In the case of sickness affecting the digestive organs, doctors are 



