Show Yl t r I THE PRESENCE OF 4 BACTERIA IN MILK I Facts Regarding Their Development and How Milk May Become Contaminated r Bacteria are so email that It Is difficult dif-ficult to form n conception of their dimensions di-mensions it Is only when wo consider con-sider them In tho i aggregate that c + they reach units of measure with which we are familiar fa-miliar It Is estimated esti-mated that If 25 000 average sized rod slhaped baclerh were placed mil to ° 01 end thelrcomhtncd length would equal an Inch The weight of nn average bacillus Is so small that it has been estimated It would take over 600000 000000 of them to influence of Tern equal ono gram perature on sac or IG800000000 terla Ordinarily 000 10 weigh one Found In Milk ounce i What the bacteria lack In size Is made up In their great numbers and powers of reproduction A cubic centimeter centi-meter of milk which contains about 25 drops frequently contains thousands sometimes millions even hundreds of millions of bacteria A single drop of sour milk may contain 40000000 bacteria Bacteria reproduce themselves by u very simple process known as fission Tho cell becomes elongated and a partition par-tition wall Is formed across the middle mid-dle Thotwo cells thus formed separate sepa-rate and we have two bacteria Higher plants may take weeks and months ore or-e o 0 0 o c O I Fig 1Bacterla of the Spherical or Coccus Type oven many years to grow to maturity These simple plants known as bacteria bac-teria however under favorable conditions condi-tions may complete their growth and reproduce themselves In less than an hour Tiierelation of bacteria to temperature tempera-ture is most Interesting und Important A certain amount of heat Is essential and a certain amount Is fatal Each particular variety of bacteria has an upper and a lower temperature limit beyond which It does not grow and a certain temperature called the optimum op-timum at which It grows best Most forms occurring In milk find their optimum temperature between 80 and 98 degrees Fahrenheit Few bacteria bac-teria grow at all above 100 degrees and at 125 degrees the weaker ones soon die An exposure of ten minutes at 160 to 160 degrees Fahrenheit is fatal to nearly all bacteria which do not form spores Spores as previously mentioned are destroyed only by prolonged pro-longed boiling exposure to steam under un-der pressure or to a high degree of dry heat With dry heat such as Is obtained in an oven much higher temperature tem-perature and longer exposures are necessary nec-essary to secure the same results In the laboratory small flasks of milk ari sterilized by holding them In a small steam boiler at a temperature of 248 degrees Fahrenheit for 15 minutes See Fig 5 If the milk Is cooled and held at 50 degrees Fahrenheit or better still 40 degrees growth Is checked at once end multiplication is very slow fit C J o ee e 8 I Fig 2 Bacteria of the Coccus Type Hanging Together In Chains It has been assumed by many wrl ters that milk is formed in the udder entirely from bacteria This has frequently fre-quently been disputed and Is still n matter of some doubt However the best authorities agree that milk Is bacteria lieu when fanned unless the udder Is so Injured or diseased that there is u direct passageway from the blood vessels to mill ducts It should bo remembered that an Injury so alight that It would escape the most careful examination might be sufllclent to allow the passage of bacteria Even If the milk Is secreted bacteria free It Is very dllllcnU to obtain It perfectly sterile Bacteria work their way Into the milk cistern through the opening In the tent and find there conditions under which they can grow and multiply This growth is ordln arlly confined to the lower part of the udder and the greater number of the bacteria are washed out with the firs a few Ktiooins of milk Sometimes 1iaw li ec the growth tuny extend Intolfao I i I smnllei milk duct and the last nor n-or the mill will contain nearly as many bacteria us the first 1 Inflammation of the udder or fcrws tntlon of the milk In the udder rarely < < i occurs because there Is only a very a small amount of milk held In I the alder al-der and most of the bacteria found there havo little or no effect on milk It Is also trim that fresh milk like UM blood contains saute substance which I has an Inhibiting Itilliiciico on bacteria j This liilluGiirt Is so slight Unit It fa j b 1 I f + Fig 3 Typical RodShaped Bacteria Bacillus Type In Some ofTheM Spores Are Shown as Clear Areas probably of little practical Importance but It may have some relation to the + comparatively slow development of S macterla In the udder The real contamination occurs after the milk has left the udder In spilo of careful milking dirt particles of dust hairs oven bits of manure from the flanks or udder of the cow may full Into the milk All of these things Invariably carry more or less bacterial contamination Manure usually contains con-tains large numbers of bacteria many t of them being kinds which produce very undesirable changes In milk and the dry dust of the stable floor contains con-tains great numbers and varieties cf bacteria This dust soon settles and an open milk pall catches a surprisingly surpris-ingly large amount But the contamination does not end here The palls or the cans may not be propel cleaned and tho corners or 1 seams may hold small particles of dirt or sour milk These Impurities are full of bacteria whicH quickly ODd their way Into the milk The cloUt through which the milk Is strained may not have been properly scalded and the bacteria lire not only pot all destroyed but have actually multiplied In the damp cloth When the strainer Is used again many of those bacteria are washed out by the milk If a cooler Is used It may add to the contamination if it is placed so that It catches the dust Finally the bet Z Fig 4 Bacteria with HairLike Appendages Ap-pendages Which Enable Them to Swim About In Water or Milk ties In which the milk Is distributed may not have been properly washed and steamed and thus may become another an-other source of contamination The contamination from each individual indi-vidual source may be small but taken all together It has a serious influence on the quality of tho milk If extraordinary ex-traordinary precautions are taken la prevent contamination the number of bacteria In the fresh milk may be kept t down to n few hundred per cubic centimeter cen-timeter with careful milking it may easily be kept within a few thousand with careless milking and handling the number will vary greatly with circumstances circum-stances and may exceed 100000 The bacteria in milk from cown kept in stables may be different from tho bacteria from cows on pasture Bacteria which occur rarely In milk during the winter months may become numerous in the summer and specific II fermentations which are almost unknown un-known III tho summer may appear In r the autumn or winter It should not be assumed that all bacteria are harmful either to milk or to the human system In fact many kinds of bacteria will grow In milk for a long time without changing its taste n or appearance while many of tho fermentations fer-mentations which make milk multsir able far direct consumption arc used fI In making butter and various kinds ol cheese Very few of the bacteria tIi < cause disease or produce poisonous byproducts by-products f t + |