Fn er re a = SSeS Copyright N° COPYRIGHT DEPOSE: agli " ae oh i iS a seni el) atari Ha tate nf PAS ia) SUaTen Aan Rae NA Nie Re nh aa i ; EN ga a ike slits ee RA a AN r Re FAG me i) os DTS Saati th Miaka aA ECLA a Gs iis stp ie One Metis Any * i “Au HI nD * en EA AEA NTC HI ; My We AYN ayy Ay i N Uy f 1 iy AS fy uh ASE Unes hal) Roars QBN E i iy ihe We St uaa ifs HK wa RE eC HAVA SH sea ee Aine iy Pea as ets } ; : ; AIH Hi Ry a ee Kil EVO Ae it Nal me te ; [ xi ie ena Peat a ahs Horie a i ine aii i i ri A A | v4 4 i Y 5 ee y FATEH Vat a HST a HY i = Wei eae ice (4 he) gig 5 Teas Nee Pst, als eine Aer AL Oe Pita UAL REIN y thy, ao i t hy } ves a ue { 4 an Nay ) Pah ah i : j y ii Ni PRINCIPLES AND PRACTICE OF MILK HYGIENE BY LOUIS A. KLEIN, V.M.D. PROFESSOR OF PHARMACOLOGY AND VETERINARY HYGIENE IN THE SCHOOL OF VETERINARY MEDICINE AT THE UNIVERSITY OF PENNSYLVANIA, AND DEAN OF THE FACULTY 41 ILLUSTRATIONS IN THE TEXT ° D a PHILADELPHIA AND LONDON J. B. LIPPINCOTT COMPANY COPYRIGHT, I9I7, BY J. 8S. LIPPINCOTT COMPANY PRINTED BY J. B. LIPPINCOTT COMPANY AT THE WASHINGTON SQUARE PRESS PHILADELPHIA, U.S.A. tf OCT 29.1917 Oca477228 PREFACE In this book an effort has been made to present systematically, in concise form, the facts and principles which are of importance in the practice of milk hygiene and to describe how they may be applied in the inspec- tion of dairy farms and in the examination of milk. The material has been obtained from various sources. Jen- sen’s “ Milk Hygiene,” Savage’s “ Milk and the Public Health,” Conn’s “ Practical Dairy Bacteriology,” Swith- inbank and Newman’s “ Bacteriology of Milk,’ King’s “ Ventilation,” Van Slyke’s “ Modern Methods of Test- ing Milk and Milk Products,” Grimmer’s “ Chemie und Physiologie der Milch,” Rievel’s “‘ Milchkunde,” Weig- mann’s “ Mykologie der Milch,” Ernst’s “ Milchhygiene fiir Tierdrzte,’’ Sommerfeld’s “ Handbuch der Milch- kunde,” and Barthel’s “ Methoden zur Untersuchung von Milch und Molkereiprodukten ” have been freely drawn upon, while articles by numerous research workers which have appeared in the various journals and official reports have furnished many important facts. To all of these authors and investigators due acknowledgment is made. The book is intended primarily as a text for students taking a course in milk hygiene, but it is the hope of the author that it will also prove of service to dairy mspec- tors, milk examiners, public health officials, dairymen, milk distributers, and others interested in the production of wholesome milk. Louis A. KLEIN PHILADELPHIA, Pa. SrertemBer 15, 1917. Ang Chia) Hae MY Ae ate DH Hi AS WEN aL 7; SR TN Mab KAN FN) Ny ai AN Heh US RNG by Ne NEN a ua) DANN ui ’ Wi Res Oath tye ( LY Kies ra) OWN} NEN UAV AD a ie i ays wy Airieay WAS! Wi) ad) Hae Ahinih neh UMP DARIN ANNE ray ti Aycan way sii MRS CR DON A i HANH Wah i HA) | t : " IN Ny, Nn SW ep iN Ney REID NN DTaP RiLe yh Ness aN } Way yy) Ha htt } Mas ny A LEX h RR Cn wa) HD ii PRONE aa WANT \ Hii ye Ve Peery, CHAPTER CONTENTS I. Paystotocy or Mik SECRETION................... Udder Structure and Cell Activity. Stages of Lactation. Phases of Milk Secretion. EG OOS TRUM Ren Ree perte Ape ek ce trxtl ANIC RUA eARA NB eG a (ATA 2 Physical Properties; Chemical Properties; Micro- scopic Appearance; Ferments or Enzymes; Change from Colostrum to Milk; Judgment of Colostrum as a Food for Man. FREDO meV Ticrisrceer rere PRI UI nC EAC ATOR SUSI LH AMA MMU ED SAG U8 Chemical Properties: Constituents; Variations in Composition; Reaction. Physical Properties: Color; Odor and Taste; Specific Gravity; Refrac- tion; Viscosity; Freezing Point. Microscopical Appearance of Milk and Milk Sediment: Cellular Content; Number of Cells. Biological Properties of Milk: Ferments or Enzymes; Original and Bacterial Ferments; Diastase; Peroxydase; Cata- lase; Reductase; Antibodies or Immune Bodies; Germicidal Action of Milk; Toxins; Aggressins. Classes or Grades of Market Milk: Certified Milk; Inspected Milk; Pasteurized Milk; Grade A; Grade B; Grade C. TONY A BY Cor ohh O56 65 GOING O05 < Qh na, ON ye NE a a Common Milk Bacteria: Acid-forming Bacteria; Gas-forming Bacteria; Peptonizing or Casease Bacteria; Alkali-forming Bacteria; Inert Bacteria. Variations in Number and Kind of Bacteria: Original Contamination; Temperature; Age of Milk; Proportion of Different Groups of Bacteria. OA RY Gerdace's 8 Dhan at bY og We tue aUMr iad UE Ay Tt Ae Rae ute OST uae SRC RRe MKS a Milk Defects Which are Present in Milk when it Comes from the Udder: Cow-like, or Salty, Cow- like Taste; “Fishy”? Milk; Rancid Milk; Slow- creaming Milk; Premature Curdling; “Gritty” or “Sandy” Milk. Milk Defects which Appear After the Milk is Drawn from the Udder: Bitter Milk; Viscid, “Ropy,” or “Stringy” Milk; “Soapy” Taste; Failure to Sour and “Butter;’’ Stable-like, Vv 11 14 50 66 vi CONTENTS Turnip-like and Beet-like Tastes, and a Burnt or Malt-like Taste and Odor; Blue Milk; Red Milk; Yellow- or Orange-colored Spots; Yellowish-green Discoloration; Greenish-Yellow Spots; Violet- colored Spots. VI. InFuveNcre or Disease Upon Mirk................ 72 Diseases of Cattle Transmissible Through Milk: Tuberculosis; Aphthous Fever or Foot and Mouth Disease; Cow-pox; False Cow Pox; Furunculosis of the Udder; Anthrax; Rabies; Actinomycosis; Milk Sickness or Trembles. Diseases of Cattle which may Render Milk Harmful to Man: Inflammation of the Udder (Mastitis); Blood in Milk; Gidema of the Udder; Indigestion; Spoiled Feed; Septic or Hemorrhagic Enteritis; Septic Metritis; Retained Placenta; Infectious Abortion; Other Diseases; Excretion of Medicines Through the Udder. Diseases of Man Transmissible Through Milk: Typhoid Fever; Paratyphoid Fever; Diphtheria; Septic Sore Throat; Scarlet Fever; ‘Tuberculosis. VIE Datey Harn JINSPECTION ee a a evans 126 Stable: Exterior; Interior. Cows: Examination for Cleanliness; Stage of Lactation; Examination for Symptoms of Diseases. Stable Practices: Method of Cleaning the Stable; Cleaning the Cows; Methods of Milking; Feeding; Bedding. Milk House: Location; Construction; Apparatus; Water Supply. Score Cards. MERE OP ASTHOREZATION CC) MOVE WG ONE Tage tea NS A 203 Principles of Pasteurization: Effect of Heat on Pathogenic Organisms; Effect of Heat on the Common Milk Bacteria; Toxins and Decomposi- tion Products; Nutritive Properties; Ferments or Enzymes; Taste; Cream Line. Methods of Pas- teurization: ‘“‘Flash”? or Continuous Process; ““Holder’”? Process; Pasteurization in the Final Container; Types of Pasteurizers; Biorization; Ultra-violet Rays; Electricity; Ozone. IX. Meruops or Examinina MILK.................... 223 Collecting Samples; Preserving Samples; Stable or Herd Samples; Individual Samples; Mixing the Milk Sample; Color, Consistency; Odor and Taste. Determination of Specific Gravity; Determination of the Per Cent. of Fat; Determination of Total APPENDIX CONTENTS Solids; Determination of Solids Not Fat; Deter- mination of the Specific Gravity of the Solids; Determination of the Per Cent. of Fat in the Total Solids; Determination of the Degree of Adultera- tion; Tests for Nitrates and Nitrites; Detection of the Usual Adulterations; Determination of the Re- fraction Number; Determination of the Reaction; Tests for Preservatives; Standard Methods of Counting Bacteria; Examination for Streptococci; Examination for Coli; Examination for Tubercle Bacilli; Fermentation Test; Estimation of the Number of Leucocytes; Boiling Test; Alcohol Test; Catalase Test; Reductase Test; Fermentation Reductase Test; Diastase Test; Tests for Heated Milk; Examination for Dirt; Test for Lactose; Ex- amination for Coloring Matters. Silelie! lee, ee) 0) @))\e\\0)\e Jollee) ele ©) |e) 10,6. || 9, \0\)e) 16) 0) 0)) e) <0)\\e| @) 10 0/10) 0! «| ©] a0 (8), 0) 0 e610, Methods and Standards for the Production and Distribution of “Certified Milk”: Organization of Medical Milk Commissions; Hygiene of the Dairy; Transportation; Veterinary Supervision of the Herd; Bacteriological Standards; Chemical Standards and Methods; Methods and Regula- tions for the Medical Examination of Employees, Their Health and Personal Hygiene, Vii 303 ANE i a Mi Wi a aye Sie Mia hey pet) Aah fit irae le Nea i ILLUSTRATIONS HALFTONES PAGE . Alveoli of the Udder in Cross-section.................. Q . Cross-section of an Alveolus of the Udder at the Time OMATLITICIOME teers ie aa yee ds ieee Cm AT Sas 1 ACS Q Involution of the Udder of an Old Cow................ 3 mrxtremity ol the Maik @istern:, 0.0605 set4 0 doe 3 meeolonres! of ‘ColavAcrovenes. 4) 3) oe ey 54 ME OlOMieskOlee Toles VULGarUs 8 and Salekic ke wes se eel 54 mineral or ouble-tube’ Cooler... fa. 0 ese. cee)! 186 MeV arious by pes| or Wirt esters.) yy les) qe ee 300 TEXT CUTS . Preparation Showing Streptococcus Lacticus or Bacterium ER CHIS PA CTO Ur ee bike Oe a 53 . Preparation from Sediment from a Cow Affected with Catarriralel Vita Stitiss sae ie ee et Lande 53 9. Inlet in a Wall Already Constructed; Inlet in a Wall Being Built, and an Outlet Shaft with Two Openings.. 132 10. An Outlet Flue Hinged at the Ceiling................. 134 Memeross-sectiomolyotabley Bloor ee yo ee wae 142 12. Window Arranged to Act as Fresh Air Inlet............ 147 EomOpenior Wneovered balbyne set w ol Te Gay 2 ia 14. Covered-top Pail with Opening Nearly Horizontal...... 171 15. Covered-top Pail with Vertical Opening............... 172 16. Another Variety of Covered-top Pail.................. 173 17. Floor Plan of Conveniently Arranged Milk House...... 181 ie Cooleriot Conical Mype ree eins eae ile eo Mics Seas LN 183 Hom Courugated by peo Cooler yi nie as aes oka 184 20. Tubular Cooler, with Continuous Surface.............. 185 22. Section Showing Relation of Water Table to Surface Irreg- IAEIEIES AM ee eee U ae On Guna e en? Cong. U0 UAC ute 194 23. How Springs May be Polluted by Subsurface Drainage.. 195 AAU hasteurizer/OL DIMplewDypen isis) bk os de eld es 216 eM LASLCUITI ZED pho Nae Nel oleae oe He ada Alig Al Q17 ILLUSTRATIONS SPaste uri zeny. iio nen ma SMV Ge Ciules ae Te Nast a aa Page 218 w Regenerative Cooler ie ns Aas 219 A; Stmple Holding Tanke ein Us nae 220 wiRetarderiof the Dank Type niece ay in) a eae Q21 . A Combined Pasteurizer and Holder.................. 221 “'@uevenne’s actometer sci ices eT ADn 0a ae 228 wiWestohal Balance sie i OQur iss Auk aioli cuatn Lule ie 232 . Modern Type of Babcock Milk-testing Bottle .......... 234 . Pipette Used in Babcock Test for Measuring Milk...... 234 . Cylinder Used in Babcock Test for Measuring Acid..... 235 . Bottle and Pipettes Used in Gerber Test............... 237 UM eser’s (uactoscopes sii UNM aD TUT A enn UN Sse 239 . Zeiss Dipping Refractometer.....................00.5 251 . Sediment Tube Used in the Trommsdorff Test.......... 283 . Gerber-Lobeck Catalase Apparatus................... 288 PRINCIPLES AND PRACTICE OF MILK HYGIENE CHAPTER I PHYSIOLOGY OF MILK SECRETION CrrTAIn facts concerning the physiology of milk secretion are of importance in milk hygiene. These will, therefore, be briefly presented. Udder Structure and Cell Activity—The udder or mammary gland of the cow consists of a large number of alveoli or acini arranged in lobules or groups and held together by connective tissue. The alveoli of each lobule communicate with a common duct which, after emerging’ from the lobule, continues its course in the interlobular connective tissue toward the milk cistern. The ducts from the several lobules unite to form the larger milk canals. The latter increase in size as they approach the milk cistern, in which they terminate. From the bottom of the milk cistern, a short, narrow canal, called the teat canal, extends through the lower end of the teat to the exterior. The udder of the cow contains four of these glandular systems, one for each teat. Each glandular system is spoken of as a “ quarter.” The alveoli are lined with glandular epithelial cells which, in the actively secreting udder, are separated from the capillaries by only a thin basement membrane. These cells select from the blood circulating in the capillaries certain materials which they convert into those substances 1 2 PRINCIPLES AND PRACTICE OF MILK HYGIENE which are peculiar to milk. They also take from the blood, water and other substances which are common to milk and blood. In histological sections, the milk fat may be observed within the actively secreting cells in the form of small fat droplets (Fig. 1). The other con- stituents of milk, being without form, cannot be seen, but their presence in the cells is indicated by a granular or turbid condition of the protoplasm. When the cells of an alveolus become filled with secretion, the cell-pro- toplasm contracts and the contents is discharged into the lumen of the alveolus, after which secretion again begins. The different stages of cell activity do not occur in all of the alveoli at the same time; different alveoli in the same lobule may show various stages. Secretion continues until the cells are exhausted, and it then ceases until the cells can recuperate. In the course of time, after repeated periods of activ- ity, exhaustion and rest, the epithelial cells of the alveoli are worn out and secretion stops in one alveolus after another. This change is called involution. In young cows the worn-out cells are regenerated. The alveoli then present the same appearance microscopically as is observed at the time of parturition (see Fig. 2). The interalveolar connective tissue is increased in volume and contains many leucocytes. Leucocytes are also numer- ous in the alveoli, together with exfoliated epithelial cells, free nuclei, parts of disintegrated cells, fat globules, and coagulated casein. Fat droplets may be observed within some of the leucocytes. By their amoeboid move- ment the leucocytes migrate from the interalveolar con- nective tissue into the interior of the alveoli, passing between the epithelial cells; and the same movement enables them to take up fat droplets and carry them Fria. 1.—Alveoli of the udderin cross-section, showing: (A) fat-droplets in the epithelial cells, (B) division of the nucleus, (C) a leucocyte in an epithelial cell, (D) epithelial cell with protoplasmic projection, alveolar content with (Z) cells and (F) free fat, and (G@) interalve- olar connective tissue. (From Chemie und Physiologie der Milch, by Dr. W. Grimmer.) _ Fie. 2.—Cross-section of an alveolus of the udder at the time of parturition. (A) epithelium, (B) basket cells, (C) leucocytes, (D) nuclei of connective-tissue cells, (£) blood capillary. (From Chemie und Physiologie der Milch, by Dr. W. Grimmer.) Fic. 3.—Involution of the udder of an old cow. (A) epithelium, (B) leucocytes, (C) blood capillary, (D) interalveolar connective tissue. (From Chemie und Physiologie der Milch, by Dr. W. Grimmer.) B Fre. 4.—(A) Funnel-shaped, (B) bell-shaped extremity of the milk cistern. (From Chemie und Physiologie der Milch, by Dr. W. Grimmer.) PHYSIOLOGY OF MILK SECRETION 3 out of the alveoli. An alveolus which has undergone involution and regeneration remains inactive until the next parturition. As the period of the secretory activity of the udder advances, the number of alveoli in this con- dition increase and the quantity of milk secreted con- sequently decreases. ‘This change occurs slowly in some cows and rapidly in others, and is commonly spoken of as “going dry.” Usually the secretion decreases until it stops altogether; the cow is then said to be “dry.” As the termination of secretory activity in the udder ap- proaches, the composition of the milk is considerably changed. Secretion of milk is also called “lactation,” and the period during which a cow produces milk is called ‘‘a lactation period.” As the cow advances in age, usually beginning with the fifth lactation, some of the worn-out alveoli are not regenerated. With each succeeding lactation an increas- ing number remain permanently inactive or break down, and the quantity of milk produced is consequently de- creased. The interalveolar and interlobular connective tissue gradually increases in volume, while the gland tis- sue decreases. (See Fig. 3.) Finally the udder becomes firm and hard and is said to be “fleshy.” A similar change is sometimes caused by disease in young as well as in old cows. Stages of Lactation.—The function of milk secre- tion is intimately related to the function of reproduction. Pregnancy stimulates the development of the gland tis- sue of the udder and secretion begins a few days before or at the time of parturition. Why the udder begins to secrete at this time is not known. Of the many the- ories advanced, that of Schein appears to be the most plausible. According to this theory, the blood of the 4 PRINCIPLES AND PRACTICE OF MILK HYGIENE pregnant cow contains certain substances called “milk- forming substances.” During pregnancy the greater portion of these substances is required for the nourish- ment and development of the foetus, but sufficient is left over to stimulate the development of the glandular tissue in the udder. When the foetus is developed, all are available for action upon the udder and secretion is stimulated. At the time of parturition the udder does not secrete milk, but a substance called colostrum. The alveoli at this period contain many cells, entire and disintegrated, and leucocytes are also numerous in the interalveolar connective tissue. The secretion is therefore rich in cells. It also contains comparatively large, round bodies which have the appearance of masses of fat grobules. ‘These are the so-called colostrum corpuscles, which are re- garded by some as leucocytes which have taken up a large number of fat globules, and by others as exfoliated epi- thelial cells containing masses of fat globules. A. cow in this stage of lactation is said to be “fresh.” During the first week the secretion gradually changes to milk. The alveoli of the udder are not all active at this time, but those which are inactive and which have not undergone permanent involution resume their func- tion within the succeeding two or three weeks, when the secretion of milk reaches its highest point. Usually by the end of the first week the leucocytes have disappeared from the alveoli and interalveolar tissue and very few cells are present in the milk. But if milking is delayed or is incomplete at any time, or if stasis of milk occurs from any cause, leucocytes again invade the alveoli and interalveolar tissue in large numbers and become nume- rous in the milk. Their appearance under these condi- PHYSIOLOGY OF MILK SECRETION 5 tions seems to be for the purpose of preventing stag- nation of milk in the alveoli; they take up the fat glo- bules in the alveoli and carry them off to the lymph stream (Czerny). leucocytes and exfoliated epithelial cells are also present in the milk in large numbers in in- flammation of the udder. Under natural conditions, the secretion of milk con- tinues only until the offspring is able to masticate and digest solid food. But in the highly specialized dairy cow, in which the function of the udder has been greatly developed, lactation may continue for as long as one to two years if rempregnation does not take place, pro- vided the milk is regularly withdrawn. When the cow is reimpregnated, lactation usually ceases within a few weeks of parturition, but in some individuals it continues without interruption from one parturition to the next. In these latter animals, the secretion changes to colos- trum a few days before parturition. Cows in which lac- tation is about to cease are called “strippers.” Near the end of lactation the milk changes very much in composi- tion and the cellular content again increases. Quite fre- quently it has a salty or bitter taste, or an animal-like taste and odor which are unpleasant. It is considered good. practice to give the udder and the organs of diges- tion an opportunity to rest and recuperate before a new lactation period begins, and “ persistent milkers ” are frequently “dried off’ about a month before the suc- ceeding parturition is due. This can usually be accom- plished by reducing the feed and gradually stopping milking. Periodical emptying of the udder is necessary for the continuance of milk secretion, and the opposite effect is produced when milking is incomplete or is omitted. 6 PRINCIPLES AND PRACTICE OF MILK HYGIENE Phases of Milk Secretion.—All of the milk obtained from the udder at one milking is not secreted before the withdrawal of the milk is begun. The average vol- ume of the cavities of the udder is 3,000 c.c., or about 3 quarts, while the average yield of milk at one milking is from 4,000 to 6,000 c.c., or about 4 to 6 quarts (F leisch- mann). A large part of the milk obtained at a milk- ing is secreted while the cow is being milked. As much milk is secreted in ten to fifteen minutes during milking as is formed during the entire period between milkings. The secretion of milk may be divided into two phases (Zietzschmann). The first phase occurs during the intervals between milkings. Following the completion of a milking, the gland remains at rest for a short time until the exhausted secretory cells can recuperate; then secretion is resumed, and gradually increases in intensity up to a certain point. The udder gradually becomes larger and firmer, but the teats remain relaxed and pendulous and contain only a small quantity of milk. The greater part of the milk secreted during the first phase remains in the alveoli and the large milk canals. There are two reasons for this: (1) the horizontal direction of the large milk canals does not favor the flow of milk into the cistern, and (2) the inward pressure of the erectile tissue in the teat causes the mucous membrane to project into the cistern in folds, filling up the cavity and opposing the flow of milk into it. When the alveoli and the milk ducts and canals be- come full, secretion decreases in intensity. Under ordi- nary conditions the pressure in the alveoli, ducts, and canals does not become sufficient to overcome the coun- terpressure exerted by the erectile tissue in the teats, PHYSIOLOGY OF MILK SECRETION 7 and consequently the milk cistern remains practically empty. The second phase of milk secretion begins when the udder is stimulated reflexly by manipulation of the teats. The udder becomes fuller and more tense, the gland sub- stance firmer. The teats lengthen and become rigid and divergent, while the wrinkles disappear from the skin covering them. The udder is distended and the cisterns are full of milk. The milk has been “let down.” All these changes are brought about by the downward stroking of the teats, which causes reflexly (1) dilation of the blood vessels and an increased flow of blood to the udder, (2) contraction of the walls of the alveoli and ducts, which forces the milk down into the cisterns, and (8) increased secretion of milk. The same effect may be produced reflexly by an irritation of the inter- nal genital organs such as may result from irrigation of the uterus or vagina, or manual removal of the pla- centa, and also by psychic influences like the sight of the calf, the clatter of the milk vessels, the sound of milk drawn from another cow into a pail, etc. When the interval between milkings is too long the milk is “let down” spontaneously, but in this case it occurs grad- ually. As soon as the milk is sufficiently “let down” the withdrawal of milk may be begun. The descending pres- sure exerted by the hand upon the contents of the milk cistern in the operation of milking opens the sphincter between the teat canal and the cistern, permitting the milk to escape. This pressure operates perpendicularly to the wall of the cistern, and when the bottom of the cistern is pointed or conical the sphincter is opened more readily than when the bottom is flat (see Fig. 4). The 8 PRINCIPLES AND PRACTICE OF MILK HYGIENE manipulation of the teats in milking causes the hyper- zemia and increased secretion set up by stroking the teats to continue until the secreting cells are exhausted, when the flow of milk ceases and the udder becomes smaller in size and relaxed. ‘The manipulation of one teat pro- duces hyperemia and stimulates secretion in all four quarters of the udder. ‘The second phase of milk secre- tion is therefore due to the mechanical stimulation result- ing from the manipulation of the teats in milking. The stimulating apparatus is in the teats, but it is not clear how the stimuli are transmitted. The udder is richly supplied with nerves from the sympathetic system and from the lumbar plexus, and yet secretion can go on after the greater part of the nerve apparatus is discon- nected. Three factors are concerned in the second phase of milk secretion: (1) The vasodilator nerves are stimu- lated reflexly by the mechanical manipulation of the teats in milking, producing a hyperemia and bringing a rich supply of milk-forming material to the secreting cells. (2) The operation of milking stimulates also the secretory and the motor nerves; stimulation of the secre- tory nerves accelerating the secretory processes in the cells of the alveoli, and stimulation of the motor nerves causing a contraction of the alveoli and ducts and forcing the milk into the cistern. (3) The “ milk-formers,” which circulate in the blood, stimulate the secretory cells (Zietzschmann). Under certain abnormal conditions the secretion of the second phase stops before the usual amount of milk is obtained. This may result from fright, sudden anx- iety, and in sensitive animals from unusual manipulation of the teats (strange milkers), from sore teats, etc. The PHYSIOLOGY OF MILK SECRETION 9 distended udder is suddenly reduced in size and becomes relaxed. This is due to a reflex contraction of the blood vessels, which reduces the blood supply, and to the empty- ing of the milk cisterns. Contraction of the blood-vessels slightly enlarges the alveoli and ducts, creating a va- cuum, and the milk in the cisterns is drawn up into the alveoli and ducts. It is then said the cow “draws the milk up,” or “will not give down.” In these cases the physiological effect of the manipulation of the teats in milking is overcome by a stronger impulse. If these impulses are repeated frequently, or are due to more or less permanent conditions, like chronic sores on the teats, the shortening of the second phase may become habitual or permanent. The secretion of the first phase is passive and slow. According to Zietzschmann, it is due to the stimulant effect upon the gland cells of the “milk-formers” cir- culating in the blood. The secretion of the second phase is active and rapid, and is instituted and continued by the manipulation of the teats in milking. Within certain limits, increasing the number of milk- ings, thus shortening the period between milkings, will increase the total daily yield of milk. If milked three times in twenty-four hours, a cow will usually yield a greater total quantity of milk per day than when milked twice in twenty-four hours. The composition of the milk is different in the first and second phases. The first milk drawn from the udder at any milking will contain a smaller proportion of solids, especially fat, than the succeeding milk. This is not due to the fat rising to the top of the fluid in the udder, nor to the adhesion of the fat globules to the walls 10 PRINCIPLES AND PRACTICE OF MILK HYGIENE of the alveoli and ducts, as has been suggested, because when milk is drawn from the udder at the end of the first phase with a milk tube or catheter the composition of the first and last milk is about the same; but as soon as the teats are manipulated, thus beginning the second phase, the per cent. of fat is increased. The milk se- creted during the first phase contains a lower per cent. of fat than that formed in the second phase. The per cent. of other solids is nearly the same in the milk of both phases. The original ferments or enzymes, except oxydase, are present in greater quantity in milk of the second phase than in that of the first. The first milk drawn from the udder contains more oxydase than the end milk. CHAPTER II COLOSTRUM Beginning a few days before and continuing for sev- eral days after parturition, the udder secretes a substance called ‘“‘colostrum,” which differs in many respects from milk. This fluid is intended for the nourishment of the ealf during the first days of life outside of the uterus of the mother. It contains a very high per cent. of albumi- nous compounds in a form in which they can be readily ab- sorbed from the digestive tract of the young animal. It also contains protective substances from the mother (Engel), which are of value in maintaining health (Im- misch), and it has a laxative action upon the bowels of the calf, which results in the removal of the meconium. Physical Properties—Colostrum is of a yellowish, reddish-yellow, or brownish color; of a thick, slimy, sticky or “stringy” consistency, with a peculiar unpleasant odor and a salty taste. The yellowish color is due to the pres- ence of fat globules, which are frequently clumped to- gether, while the reddish or brownish tinge is due to the presence of red-blood cells or blood. Containing a much greater per cent. of solids than milk, its specific gravity is naturally much higher, ranging from 1.040 to 1.080 and even up to 1.090. Chemical Properties—Albumin and globulin are present in colostrum in considerably greater quantity than in milk. Nuclein compounds are also to be found in larger proportion. There is less casein and sugar, about the same per cent. of extractives, but a greater proportion of mineral salts, The analysis, as given by 11 12 PRINCIPLES AND PRACTICE OF MILK HYGIENE Eugling, is as follows: Casein 2.65 per cent., albumin and globulin 16.55 per cent., sugar 3 per cent., extrac- tives 3.54 per cent., ash 1.18 per cent., and water 73.07 per cent. The high content of albumin and globulin is due to the presence of the colostrum bodies and nume- rous other cells. The sugar is not lactose, as in milk, but glucose, or perhaps a mixture of glucose and galac- tose (‘Tereg). Of the extractives, about 78.2 per cent. is fat, 13.8 per cent. cholesterin, and 8 per cent. leci- thin. The fat differs from that of milk and is apparently similar to the fat of the tissues. The mineral salts are rich in magnesia, to which is attributed the laxative ef- fect of colostrum. The reaction is acid to litmus. For two to four days after parturition the secretion coagulates when boiled (see boiling test), on account of the large quantity of albumin and globulin present, while it curdles for four to twelve days after parturition when mixed with an equal volume of 68 per cent. alcohol (see alcohol test). Microscopic A ppearance.—Viewed under the micro- scope, colostrum is seen to contain free fat globules, which are not uniform in size like those seen in milk; colostrum bodies or corpuscles, which are comparatively large, round or mulberry-shaped masses, containing fat globules; lewcocytes, some of which contain fat globules, and, in fresh colostrum, show amoeboid movement; and epithelial cells, which are more or less disintegrated. ‘The colostrum bodies are cells which contain large masses of fat globules within their protoplasm, but opinions differ as to whether they are leucocytes or epithelial cells. Ferments or Enzymes.—Catalase and diastase are present in colostrum in greater amount than in milk, but at the end of the first week after parturition they are COLOSTRUM 13 reduced to the amount normally found in milk. Oxydase and peroxydase may be absent for thirty hours or less following parturition, but after that time they are usually present (Gruber). The bactericidal power of colostrum is greater than that of milk. Change from Colostrum to Milk.—The secretion of the udder changes gradually in appearance and com- position until, in about a week after parturition, it be- comes milk. According to Weber, the consistency is changed to that of milk by the second to the fifth day, usually by the third; the color by the third to the eighth day, usually by the fifth, and the reaction by the seventh day, although this is variable. The colostrum bodies persist for variable periods. In some cows they continue to be present indefinitely in small number, while in others they are absent even in the first days of secre- tion. Shortly before the lactation ceases they again be- come numerous. Judgment of Colostrum as a Food for Man.—While colostrum is of great value to the new-born calf, it is not considered desirable as human food. It has not been proven to be injurious to the health of man, but the odor and taste are obnoxious, and its appearance is unap- petizng. Regulations of local health authorities for the control of milk supplies, therefore, forbid the sale of the product of a cow for food purposes usually for one week after parturition, and also for fifteen days before. It has been proposed by Weber that the use of the udder secretion be prohibited for general food purposes as long as it coagulates when boiled (2 to 4 days), and that its use for children be forbidden as long as it continues to react to the alcohol test (4 to 12 days). CHAPTER III MILK The fluid known as “milk” consists of water and certain solids. The latter are in solution, in suspension, and in emulsion. In order to comprehend the various changes which may occur in milk and to understand the different methods for its examination, it is necessary to have some knowledge of its physical and chemical prop- erties, its microscopic appearance, the ferments or enzymes it contains, and the bacteria with which it may be contaminated. These points will therefore be given consideration. CHEMICAL PROPERTIES Constituents.—The principal chemical constituents are casein, lactalbumin, lactoglobulin, fat, lactose, mineral salts, and water. Casein is a nucleo-albumin and therefore contains phosphorus. It is insoluble in water when free and un- combined. But in milk it is combined with calcium in the form of dicalcium caseinate. This compound, which is neutral to litmus and acid to phenolphthalein, is re- sponsible for the white color of milk, and in part for its opacity. It is not in solution in milk, but in suspension. When milk is exposed to a low temperature the calcium caseinate forms flakes, which, when the temperature is sufficiently low, are visible to the eye; it is also more readily precipitated. This must be kept in mind when the alcohol test is used (page 285). If an acid is added to milk the casein is precipitated. 14 MILK 15 The same thing occurs when the lactose in the milk is fermented by bacteria and a sufficient quantity of acid is produced. ‘The calcium caseinate is split up. The acid combines with the calcium, while the free casein, being insoluble, is precipitated in the form of a firm, jelly-like white curd. Subsequently this curd contracts and expresses a fluid called whey, which contains some of the milk fat, the albumin and globulin, the milk sugar, the mineral salts, and the calcium salt formed by the combination of the acid with the calcium. Most of the fat remains in the curd with the casein. This is the com- mon sour curdling of milk. If lime water or a dilute solution of an alkali is added, the casein will be redis- solved and the acidity reduced. Rennet or chymosin also causes curdling of milk. In this case the calcium caseinate is split up by the rennet into calcium paracaseinate and a substance known as whey-proteid. Calcium paracaseinate, being insoluble, is precipitated and forms a curd, while the whey-proteid is held in solution in the whey. Certain bacteria produce a rennet-like ferment, which splits up the casein com- pound of milk in the same manner. This is the sweet curdling of milk, so called because the milk curdles with- out souring. The curd produced in this way cannot be redissolved by lime water or a dilute solution of an alkali. Curdling of milk may occur from the joint action of acids and the rennet-like ferment. The blood contains a ferment, called anti-rennet, which inhibits the action of rennet. This ferment is not present in normal milk, but when inflammation occurs in the udder and there is a transudation of serum from the blood-vessels into the udder tissue the anti-rennet ferment is present in the udder secretion, which is then not coagulated by rennet 16 PRINCIPLES AND PRACTICE OF MILK HYGIENE at all, or only after several times the usual amount of rennet is added. A method based upon these facts has been proposed by Schern for detecting milk from cows affected with mastitis, but the test has not come into very general use, because it has not been found possible to obtain a standardized rennet solution which will not deteriorate. Fresh milk may be heated to boiling without coagula- tion occurring. A thin membrane, which consists prin- cipally of casein, forms on the surface, but real coagula- tion does not take place. After a certain degree of acid- ity has been reached a temperature of 75° C. (167° F.) is sufficient to coagulate the casein. Casein is formed by the secreting cells of the alveoli of the udder from the circulating albumin of the blood (Rievel). Lactalbumin.—The albumin of milk is in solution. It is similar to the albumin of the blood, but differs slightly in its chemical composition and polarization. It begins to coagulate at 65.6° C. (150° F.), and the coagulation increases with the temperature (Rupp). Whether the albumin originates from the breaking down of cells or is derived from the blood is not known. Lactoglobulin—The globulin of milk originates from the disintegration of cells, and is present in milk in solution. It coagulates at 75° C. (167° F.). Fat.—The fat is present in milk in an extremely finely divided condition—7.e., in an emulsion. Under the microscope it can be observed in the form of small globules. The specific gravity of the fat is lighter than that of any of the other milk constituents, including the water, being only 0.98. Consequently the fat globules in milk are buoyant, and when the milk is permitted MILK 17 to stand undisturbed they rise to the top and in a very short time form a layer on the top of the fluid, which is known as the cream layer or the cream line. By many consumers the quality of milk is judged solely by the thickness of the cream layer. When the cream is re- moved the remaining fluid is called skim milk; or it is called separator milk when the cream is removed by a centrifugal apparatus known as a separator. The fat globules vary in size with the breed, the stage of lactation, the feed, at different periods of the same milking, and with the individual. In the milk of Jersey and Guernsey cows the fat globules are larger than they are in the milk of Holsteins and Ayrshires. The cream rises more rapidly when the globules are large than when they are small. Moderately high temperatures alee, favor the sepa- ration of the fat feiapules from the remainder of the milk; therefore when milk is to be run through a sepa- rator it is usually warmed to 32° C. (90° F.). On the other hand, higher temperatures delay or entirely pre- vent the formation of a cream layer. Temperatures above 70° C. (158° F.) destroy the cream line entirely. A temperature of 65° C. (149° F.) for ten minutes has no effect, but as the time of exposure at this tempera- ture is increased the formation of the cream layer is delayed more and more, until finally, after forty min- utes’ exposure, it does not form at all. Milk may be heated at 63° C. (145.4° F.) for thirty minutes and at 60° C. (140° F.) for as long as fifty minutes without affecting the cream line. The cream does not rise in homogenized milk because the fat globules have been broken up into fine particles. Such milk is said to be more palatable and more digestible than ordinary milk, 2 18 PRINCIPLES AND PRACTICE OF MILK HYGIENE but these advantages are overbalanced by the expense of the process. When milk is shaken or agitated the fat globules gradually unite and form flakes or lumps—.e., butter. Small clumps of butter fat may form in milk during transportation when the container is not full. This change may affect the test for fat. If milk or cream is slightly acid and warm, the clumping of the fat glo- bules is facilitated. Hence cream is usually churned after it has attained an acidity 0.4 per cent., and at a temperature of 21° C. (70° F.). Cream from a cow near the end of lactation may not “butter’’ because of its alkalinity. The fat of milk differs in its chemical and physical properties from both the fat of the tissues and the fat of the food. It consists of a mixture of fats, princi- pally olein, stearin, and palmatin, together with some butyrin and other fats. Its composition varies, being influenced by the breed, feed, external conditions, etc. Cotton-seed meal, for example, increases the olein and raises the melting point. When milk fat decomposes, butyric acid is liberated and produces a rancid odor and taste. The color of the milk fat is more or less yellow. The fat globules, by reflecting the light, are partly re- sponsible for the opacity of milk. In regard to the origin of the milk fat, it appears most probable that it is derived in part from the splitting up of albuminous compounds in the udder or in another part of the body, or in both places. It may also be formed from the carbohydrates which are carried to the udder by the blood (Rievel). Lactose.—This substance, also known as “milk 99 sugar,” is in solution in milk. It is a disaccharid and MILK 19 may undergo different varieties of fermentation when acted on by microdrganisms. Certain bacteria split up lactose into lactic acid and certain by-products (carbon dioxide, hydrogen, formic acid, butyric acid, etc.). These organisms are the cause of the common “souring” and curdling of milk. ‘The bacteria of the coli-aerogenes group ferment lactose and form acids and gases (lactic, acetic, and succinic acids, carbon dioxide, carburetted hydrogen, oxygen, and nitrogen). Under normal conditions, lactose is found only in the milk. If milk is retained in the udder from any cause, as incomplete milking, omission of milking, udder disease, etc., then lactose appears in the urine. When a secreting udder is completely extirpated, glucose is tem- porarily present in excess in the blood and appears in the urine, while lactose appears in the urine if the udder tissue is not completely removed. These latter facts are taken to indicate that milk sugar is formed in the udder from the glucose carried to it by the blood. Salts.—The salts of milk, which are in solution, are very largely inorganic. Calcium, potassium, and sodium, together with small quantities of magnesia and oxide of iron, are present in combination with phosphoric acid, sulphuric acid, chlorine, and carbonic acid. A small por- tion of the basic substances is in combination with citric acid and probably with other organic acids. W ater.—The water of milk is derived from the blood. The milk constituents, except the water, are referred to as the milk solids, total solids, or dry matter. The casein, albumin, globulin, lactose, and salts are desig- nated as solids not fat. Variations in Composition.— While normal milk always contains the same chemical constituents, the proportions 20 PRINCIPLES AND PRACTICE OF MILK HYGIENE in which they are present vary very much. 'The fat shows a greater variation than the other solids. In milk rich in total solids, the fat content is frequently considerably above the average, while the per cent. of solids not fat only slightly exceeds the average. On the other hand, in thin, poor milk the fat per cent. may be far below the average, while the per cent. of solids not fat is not very far from the average. Milk from individual cows shows a greater variation in composition than different samples of market milk, which is a mixture of the milk from a number of cows. Individual milk may show the following variations in the proportion of the different constituents: fat, 2.5 to 7.5 per cent.; lactose, 4 to 5.8 per cent.; casein, 2 to 5 per cent.; albumin, 0.39 to 0.95 per cent.; globulin, a trace; salts, 0.35 to 1.21 per cent.; water, 83 to 89 per cent. The fat content shows the greatest range of varia- tion and the lactose the least. These variations must be taken into consideration in collecting samples of milk for certain tests and in judging the results of tests for adulteration and skimming. They are due to a number of causes. Some of these causes, such as the breed, individuality, and stage of lactation, are more or less regular and con- stant in their operation. As a rule, cows of the Jersey and Guernsey breeds give milk richer in fat than Hol- steins and Ayrshires, but some individuals of the Hol- stem and Ayrshire breeds give milk with a higher fat content than some Jerseys and Guernseys. Early in the stage of lactation, when the milk flow is most abundant, the proportion of solids, especially the fat, is less than it is later, when the milk flow has decreased. Instances MILK 21 are known where the addition of several “fresh” cows to a small herd at the same time has reduced the fat per cent. of the mixed milk below the standard formerly maintained. In the last month of lactation, when the secretion decreases rapidly, the proportion of solids usually increases, especially the fat. At the same time, the secretion reacts decidedly alkaline to litmus paper and usually has a salty taste; sometimes it has an animal- like odor and taste. Cows in this stage of lactation are called “strippers.” In exceptional cases the milk does not show any noticeable change in chemical composition during the entire period of lactation, while in rare cases the per cent. of solids may decrease at the end of lacta- tion. At different stages of the same milking the milk also shows a regular and constant variation in composi- tion, the first milk drawn containing a lower per cent. of fat than the last or “end” milk. Incomplete milking may lower the per cent. of fat, because the end milk is much richer in fat than the first milk. Transitory and irregular variations in composition may be observed in the milk of the same cow from day to day, or even in the milk drawn at different milkings on the same day. The fat content may show a difference of as much as one per cent. These variations are attrib- uted to change in the character of the feed, or in the time of feeding and watering, change of milkers, the weather, change of stable, and unusual occurrences (storms, stran- gers, etc.). The quantity of milk secreted is also affected by the same causes. While the feed has no pronounced permanent effect on the composition of the milk, a change from dry to green feed may cause a temporary increase in the fat of from 0.5 to 1 per cent., while distillery slops 22 PRINCIPLES AND PRACTICE OF MILK HYGIENE or other very watery feed may cause a temporary de- crease of from 0.25 to 0.5 per cent. The tame of milking will influence the composition of milk. When the intervals between the milkings are equal and the feed, amount of water, etc., are the same, there is no difference between the composition of the morning and evening milk; but in practice the periods are usually unequal, ihe shorter interval preceding the morning milking in the summer and the evening milking in winter. At the milking following the shorter interval the quantity of milk obtained is less and the fat per cent. is greater than at the other milking. Hence it fol- lows that in summer the morning’s milk is richer in fat but of lesser quantity than the evening’s milk, while in winter the reverse is true. The age of the cow has no appreciable effect on the composition of milk. Volun- tary ewercise in the open air increases the fat per cent. as well as the quantity of milk yielded; forced exercise decreases the water in the milk and consequently de- creases the volume of the milk flow, but the per cent. of fat is increased, while violent exercise reduces both the volume and the per cent. of solids. The effects of @strum are not uniform; the fat may be increased or decreased, the albumin may be increased to such an extent that the milk will curdle when boiled, or there may be no change in the composition. In one test of milk from a cow with nymphomania the proteids were increased to 5.72 per cent. Weaning, or removing the calf, when it causes the cow to become restless and fretful, is attended with a decrease in the fat per cent. The variations in quantity and composition caused by disease will be considered in the chapter on the “ Influence of Disease on Milk.” Market Milk varies less in composition than indi- MILK 23 vidual milk, because the different variations in the milk of individual cows balance one another more or less. Under certain conditions, milk from different herds, 7.e., herd milk, may show a greater variation in composition than the mixed milk of several herds. For example, milk from a Jersey or Guernsey herd will usually show a higher fat content than milk from a Holstein or Ayr- shire herd. ‘The presence of a large proportion of “fresh” cows in a herd at one time may cause the mixed milk of the herd to be low in solids, especially fat, while a large proportion of “strippers” may have the opposite effect. The per cent. of fat in market milk may range from 3 to 5 per cent., and the per cent. of solids not fat from 8.5 to 10.5 per cent. The average composition, as reported by Flieschmann, is: fat, 3.4 per cent. ; lactose, 4.6 per cent.; casein, 3 per cent.; albumin, 0.5 per cent.; globulin, a trace; salts, 0.75 per cent.; water, 87.75 per cent. Over 5000 samples of milk examined at the New York State Experiment Station at Geneva, N. Y., were found to contain an average of 3.9 per cent. of fat, 5.1 per cent. of lactose, 2.5 per cent. of casein, 0.7 per cent. of albumin, 0.7 per cent. of salts, and 87.1 per cent. of water. Although it is unusual, normal market milk may fall below the usual limit for solids, especially fat, particu- larly milk from a single herd, under some of the condi- tions mentioned above. For this reason, difficulty has at times been experienced in legally proving that milk has been skimmed or diluted with skimmed milk or water, and this has led to the adoption of legal standards for milk and other dairy products by different states, the United States government, and some municipalities. 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The standards for milk and other dairy products adopted by the various states and territories, as reported by the United States Bureau of Animal Industry, will be found on pages 24 and 25. Reaction.— The reaction of milk is amphoteric to lié- mus—t.é., it turns blue litmus red (acid monobasic phos- phates) and changes red litmus to blue (alkaline di- basic phosphates). To phenolphthalein solution it is acid. When phenolphthalein solution is added to milk, no color reaction occurs, because the color of phenol- phthalein solution is not changed by acids. But if, after the addition of phenolphthalein solution, sodium hydrox- ide solution is added to the milk in excess of the amount necessary to neutralize the acidity the fluid assumes a pink color, which is permanent. This reaction is made use of in determining the degree of acidity of milk and cream. To neutralize the acidity in 100 c.c. of normal, fresh market milk, 18 to 19 c.c. of a one-tenth normal solution of sodium hydroxide are required. This represents an acidity of 0.16 to 0.17 per cent. The acidity of milk when it is drawn from the udder is less than 0.1 per cent. This original or native acidity is due to the casein and acid phosphates. The fermentation of the milk sugar by bacteria increases the acidity. Lactic or other acids formed in this manner are present whenever the acidity is over 0.1 per cent. Market milk with an acidity of 0.1 to 0.2 per cent. is considered fresh and good. In some MILK 27 cities the legal limit is 0.2 per cent. A sour taste is not present until the acidity exceeds 0.3 per cent. The acidity of colostrum is about three times as great as that of milk. As the colostrum changes to milk, the acidity gradually decreases until it reaches the point normal for milk. ‘Toward the end of lactation the acidity is further decreased, and in “strippers” is very low, or the reaction may even be alkaline. The reaction of the milk of individual cows is usually below normal in acidity, or may even be alkaline, in ordi- nary inflammations of the udder, tuberculosis of the udder, and probably also when the udder is eliminating abnormal substances, as in cowpox; but this is by no means always the case. In streptococcic mastitis the milk may be more acid than normal. The reaction alone of the milk of individual cows cannot therefore be relied upon to discover diseased conditions. It is hardly neces- sary to mention that nothing can be learned on this point from determining the reaction of market milk. High acidity in market milk is usually the result of excessive fermentation of the lactose, and is an indication that the milk is stale, or was produced under unclean conditions, or was not properly cooled and cared for. The addition of boric acid or formaldehyde also increases the acidity. Salicylic acid has less effect on the reac- tion because it is usually not added in very great quan- tity. The acidity may be reduced by the addition of alka- lies (bicarbonate of soda, chalk, potash), but the addition of these substances to milk is illegal. Addition of water and heating (loss of CO:) also reduce the acidity. (For methods of determining acidity, see pages 254 to 257.) 28 PRINCIPLES AND PRACTICE OF MILK HYGIENE PHYSICAL PROPERTIES The physical properties of milk which are of great- est importance in milk hygiene are the color, odor and taste, specific gravity, and refraction. Other physical properties which have been extensively studied are the viscosity, surface tension, freezing point, and electrical conductivity. Color.—Miulk is a white, opaque fluid, sometimes with a yellowish or bluish tinge. The white color is due to the calcium caseinate, while the opacity is due in part to the same substance and in part to the fat. Not only the quantity of fat, but also the size of the fat globules, affects the opacity, the opacity being less when the glo- bules are large than when they are small. Since opacity does not depend entirely on the quantity of fat, tests for fat based upon transparency, such as the lactoscope test (p. 239), are not accurate. The yellowish tinge of milk is due to a pigment in the fat (carotin) ; it is more pro- nounced in milk from cows of certain breeds, as the Guernseys. A bluish tinge indicates that the milk has a low fat per cent., and is sometimes associated with skim- ming and watering, but it must be remembered that any milk in a thin layer has a bluish tinge. Odor and Taste——Normal milk has a slight odor, resembling the exhalations from the cow’s skin, and a slightly sweetish taste. During the colostral period and near the end of lactation, individual cow’s milk may have a salty, bitter, or a rancid, animal-like taste. A large proportion of “strippers” in a herd may give the mixed milk a similar taste. The milk of the individual cow may also be salty or bitter in advanced pregnancy, after abor- tion, in mastitis, and when digestion is disturbed. Milk with a certain degree of acidity will acquire a bitter, MILK 29 astringent taste in rusted vessels in consequence of the formation of iron lactate. A “fishy” taste may also be present when the milk vessels are rusty or when they have not been rinsed free of soap powder. Certain aromatic feeds impart a characteristic odor and taste to the milk. Among these are ensilage, rape, cabbage, and beets, turnips, rutabagas, carrots, and their tops. This is not ordinarily due to the ingestion with the feed of substances responsible for the taste and odor and their elimination with the milk through the udder, but to the absorption by the milk of the odor of the feed from the air of the stable. ‘This is demonstrated by the fact that when these feeds are fed in ordinary quantity and after milking, and not immediately before or during milking, the odor and taste of the milk are not affected. If these feeds are given in large quantity, it is probable that some of the aromatic substances may be excreted through the udder. In the case of garlic, however, the volatile oil to which the odor of that substance is due is eliminated through the udder in the milk. Odors are readily absorbed by milk, especially when it is warm. Milk drawn and allowed to stand in an unclean or poorly ventilated stable will acquire a stable-like odor and taste. It has been demonstrated experimentally that if milk at a temperature of 14 to 22° C. (57 to 72° F.) is ex- posed to the odor of ensilage or horse manure for a half hour to an hour and a half it will acquire an odor and taste resembling these substances (Russell). Abnormal odors and tastes result also from the growth of bacteria in milk. The activity of the pepton- izing bacteria may produce first a bitter taste, due to the production of peptone, and later a foul and unpleas- ant odor and taste, the result of decomposition processes. 30 PRINCIPLES AND PRACTICE OF MILK HYGIENE Bacilli of the coli-aerogenous group may produce an unclean, even nauseating, taste with a stable or manure- like odor, while the lactic acid bacteria give to milk a sour odor and taste. Specific organisms have been iden- tified which produce bitter, soapy, oily, and burnt tastes and a stable-like odor and taste. Other bacteria produce a rancid odor and taste, and some produce an wnclean odor and taste. While some of the peptonizing bacteria (udder cocci) are normal inhabitants of the udder, the other bacteria usually enter the milk after it is drawn from the cow. Sometimes, however, bacteria which are the cause of abnormal odors and tastes become estab- lished in the udder. Odors and tastes of bacterial origin are often not apparent until a certain period after the milk has been taken from the udder and usually become more pronounced as the milk increases in age. Milk acquires a cooked taste when heated above 68 to 71° C. (155 to 160° F.) Heating in open vessels has a more pronounced effect on the taste than heating in closed vessels or bottles. The senses of smell and taste tire very quickly and cannot be depended upon to judge many samples of milk, Odors and tastes are more apparent when the milk is warm. Specific Gravity—As would naturally be expected from the statements made in regard to the variation in the composition of milk, the specific gravity or density of different samples of milk varies considerable. The range of variation is greater for individual milk than for market milk. The specific gravity of the milk of individual cows will range from 1.027 to 1.040, while that of market milk will fluctuate between 1.028 and 1.034, with an average of 1.032, at the standard tempera- MILK 31 ture of 15° C. (60° F.). At higher temperatures the specific gravity or density is decreased, and at lower tem- peratures it is increased. The specific gravity depends not only upon the total quantity of solids contained in the milk, but also upon the relative proportion in which the individual solids are present, because the individual solids are of different spe- cific gravity. Eat shows the greatest difference, being much lighter than the other solids; it is even lighter than water. ‘The solids not fat are all heavier than water, the specific gravity of the salts being 4.12, lactose 1.666, and proteids 1.346 (Richmond). Therefore the removal of fat, z.e., skimming, increases the specific gravity, and the addition of skim milk has the same effect, while the addition of water reduces the specific gravity. But the specific gravity has such a wide normal variation that it is possible to remove a small amount of fat from milk with a normally low specific gravity without causing the specific gravity to rise above the normal range, and, conversely, a certain amount of water may be added to milk with a normally high specific gravity without lower- ing the specific gravity below the normal limit. How- ever, in the first case the per cent. of fat will be decreased, and in the second there will be a decrease in both the per cent. of fat and of solids not fat. When the specific gravity of milk is raised above the normal by skimming it may be brought within the normal range by the addi- tion of water, but the per cent. of fat and of solids not fat will be decreased. Therefore, in examining market milk to detect skimming or the addition of skimmed milk or water, the per cent. of fat and of solids not fat must always be considered in connection with the spe- cific gravity. (For method of determining the specific 32 PRINCIPLES AND PRACTICE OF MILK HYGIENE gravity, see page 228.) Determination of the specific gravity of the milk solids and of the per cent. of fat in the milk solids will assist in detecting milk which has been skimmed or skimmed and watered. (See page 246 for methods.) The milk solids of normal market milk have a specific gravity of 1.31 to 1.36, and the per cent. of fat in the milk solids is 20 to 34. When milk is skimmed or skimmed and watered, the specific gravity of the milk solids is increased, while the per cent. of fat in the solids is decreased. The influence of disease on the specific gravity of individual milk is not constant, but the specific gravity is usually lowered. However, the specific gravity of individual cow’s milk cannot be made use of to discover diseased conditions, because milk from different cows shows such great variations under normal conditions. The specific gravity of milk is lower when it is drawn from the udder than it is several hours later. Refraction. Rays of light passing through one me- dium into another of different optical density, as through air into milk, are broken or refracted at the point of con- tact of the two media. The degree of refraction, or the refractive power compared with that of air, is called the refractive index. Since the calcium caseinate and fat contained in milk prevent the light rays from passing through it, these substances must be removed before the refractive index can be determined. ‘The refractive index of milk, so-called, is really the refractive index of the milk serum or whey, z.e., the milk minus the calcium caseinate and fat. The refractive power of the milk serum depends upon the quantity of lactose or of lactose and salts present. Adding water to milk reduces the proportion of these MILK 33 substances, and therefore reduces the refractive index. Hence the refractive index may be used to detect watered milk. (See method on page 249.) The refractive index of normal market milk ranges from 1.3429 to 1.3445. On the scale of the Zeiss dipping refractometer, the reading for normal milk ranges from 87.8 to 41.5. Viscosity is manifested by the adherence of milk to the sides of a glass vessel. It increases as the tempera- ture of the milk is lowered, and vice versa. It is de- creased by skimming and by the addition of water. Dur- ing the colostral period and near the end of lactation it is greater than at other times during the lactation period; it is also increased in disease or injuries of the genital organs, especially the udder. Boiling momentarily, or heating for a longer time at lower temperatures, decreases the viscosity of milk, causing it to appear thinner than normal raw milk. Cream heated at 60° C. (140° F.) for twenty minutes appears thinner and less viscous than raw cream with the same fat per cent. and will not “whip” readily. Vis- cogen, a mixture of cane sugar and lime, has been added to heated cream to overcome this change. This prepara- tion has also been used to increase the viscosity of raw cream of low fat per cent., and also to increase the con- sistency of skimmed or watered milk. The addition of viscogen to cream or milk is illegal unless the product is sold as visco-cream or visco-milk. The specific gravity of watered or skimmed milk is increased by the addition of viscogen, and the per cent. of solids not fat, especially the salts, is also increased. The acidity is reduced. Starch is also added to cream to increase the body or consistency. Freezing Point—The freezing point of milk is 3 34 PRINCIPLES AND PRACTICE OF MILK HYGIENE —0.54 to —0.57° C. (31.02 to 30.9° F.). It varies with the amount of the dissolved substances contained in the milk, especially the salts. When water is added to milk the freezing point rises, while in disease it is sometimes lowered and sometimes raised. The determination of the freezing point has as yet proven of no practical value in routine milk examination. Surface tension and elec- trical conductivity are likewise of no practical impor- tance. MICROSCOPICAL APPEARANCE OF MILK AND MILK SEDIMENT When examined under the microscope, milk is found to contain numerous fat globules with a few cells, cell fragments, and free nuclei scattered among them. If a small quantity of milk is placed in a sediment tube and centrifugalized, only a part of the cells and cell remnants are thrown down to the bottom of the tube with the heavier constituents of the milk; many adhere to the fat globules and are carried to the top, while the others remain in the intermediate fluid. According to Prescott and Breed, only about one-fourth is contained in the sediment, one-half being in the cream and the remainder in the milk. Heating the milk to 60° C. (140° F.) or above before centrifugalizing will increase the cellular content of the sediment. If some of the sediment is spread out in a thin layer on a glass slide, dried in the air, fixed by heating, and stained, the cellular bodies can be more readily studied. Cellular Content.—It will then be observed that the cells are of two principal kinds: leucocytes and epithe- lial cells. The leucocytes are of the polymorphonuclear and lymphocyte varieties, while the epithelial cells are of the pavement, cuboidal and cylindrical types. Fre- MILK 35 quently the epithelial cells are folded on themselves, when they appear as rounded, oval, or irregular shapes, and sometimes they are arranged in groups like the petals of a flower. Degenerated and disintegrated cells, free nu- clei, bacteria, and vegetable cells and fibres may also be present. Number of Cells——The number of cells in different samples of milk will vary very much. Milk from indi- vidual cows in normal condition may contain from 50,000 to 1,000,000 and over per c.c. (Savage). Milk from the same cow may show considerable differences when examined at intervals of a week or a month, and varia- tions may also be found in the milk from different quar- ters of the udder of the same cow. The number of cells may differ at different stages of the same milking, being much greater in the end milk than in the first milk. The cellular content is very high for a few days after calving. Near the end of lactation the cells again in- crease in number, and they are also present in excess after incomplete or delayed milking. In mastitis there is usually a pronounced increase in the number of cells, particularly the leucocytes. In some cases the number is as high as 200,000,000 to 300,000,000 per c.c. (Sav- age), but in others it is as low as 500,000 per c.c. The cell content of milk from an udder affected with mastitis exhibits two other features which are important, viz: the cells are clumped or grouped together, and 75 to 80 per cent. are polymorphonuclear leucocytes. Red-blood cells may also be present in the milk when the udder is very much congested, as may occur at the beginning of lactation and in acute inflammation, and also following traumatic injuries. The differences in the cell content of the individual 36 PRINCIPLES AND PRACTICE OF MILK HYGIENE milk of normal cows are likely to balance one another when the milk of several cows is mixed together; con- sequently different samples of market milk show less variation in the number of leucocytes than individual milk. On the other hand, when the milk from one cow affected with mastitis is mixed with the milk of other cows in the herd which are in normal condition, the cell content of the mixed milk is not likely to be very much increased unless the herd is a very small one or the milk from the diseased cow contains an enormous number of cells. Several methods have been devised for detecting an excessive number of cells in milk (see pages 281 to 284). When used to examine the milk of individual cows, these methods are of great assistance in discovering cases of mastitis before clinical symptoms or visible milk changes appear, but when applied to samples of mixed market milk they cannot be depended upon entirely for the purpose of detecting mastitis in the herds supplying the milk. BIOLOGICAL PROPERTIES OF MILK Ferments or Enzymes.—Milk contains a number of ferments or enzymes. Some of them resemble the di- gestive ferments in their action. ‘This class includes a proteolytic ferment called galactase, and diastase, an amylolytic ferment. These ferments are believed to assist in the digestion of milk. A tripsin-like ferment and fat-splitting ferments or lipases have been reported, but their existence is questioned. There are also oxidiz- ing ferments: the oxydases and peroxydase, and reduc- ing ferments: catalase and reductase. The diastase, MILK 37 peroxydase, catalase, and reductase reactions have been made use of in milk control work. Original and Bacterial Ferments.—In milk hygiene it is important to distinguish between original and bac- terial ferments. An original ferment is one which is secreted by the cells of the udder, or which is contained in cells like the leucocytes and becomes free in the milk when these cells disintegrate. A bacterial ferment is secreted by the bacteria which gain access to milk after it is formed in the udder. A bacterial ferment increases in quantity after milk is drawn from the udder as a result of the growth of bacteria, and if it is destroyed by heat it will again appear unless the bacteria are all killed and the milk is not reinfected. On the other hand, an original ferment cannot increase in quantity after the milk leaves the udder, and if it is destroyed by heat it does not reap- pear in the milk. Diastase and peroxydase are original ferments, catalase is both an original and a bacterial ferment, and reductase is a bacterial ferment. Diastase.—One hundred c.c. of normal milk will di- gest 0.015 to 0.02 gramme of starch in thirty minutes. This action is due to an amylolytic ferment contained in the milk, which has been called diastase. This ferment operates best at a temperature of 45° C. (113° F.) and is destroyed by a temperature of 65 to 68° C. (149 to 154° F.) for thirty minutes. It is present in the milk when it is formed in the udder, and is therefore an orig- inal ferment. It is not produced by bacteria. Colostrum is richer in diastase than ordinary milk, and the ferment is also present in greater quantity near the end of lac- tation. The end milk contains more diastase than the first milk drawn from the udder. (See diastase test on page 297.) 38 PRINCIPLES AND PRACTICE OF MILK HYGIENE Peroxydase.—If paraphenyldiamin or tincture of guaiac is added to milk with a little hydrogen peroxide, the milk at once assumes a blue color. This change occurs because the ferment contained in the milk called “ peroxydase”’ splits off oxygen from the hydrogen peroxide and this free oxygen oxidizes the paraphenyl- diamin or the guaiac to a colored compound. If the milk is heated to 80° C. (176° F'), the reaction does not occur because the ferment is destroyed. ‘The reaction occurs best at 40 to 50° C. (104 to 122° F.). Peroxydase is present in milk when it is formed in the udder and it is not secreted by bacteria. It is therefore an original ferment. (See tests for heated milk on page 298.) Catalase —This ferment, which is also known as superoxidase, possesses the specific property of splitting up hydrogen peroxide into water and oxygen. The re- action which occurs is as follows: 2H2O2 = 2H2O + Oz. Catalase is both an original and a bacterial ferment. It is secreted with the milk and is contained in leucocytes and in blood. It is also secreted by many of the bacteria found in milk, but the various species differ in their capacity to produce the ferment. The putrefactive or- ganisms appear to produce it in the greatest quantity. The ability of the lactic acid bacteria to produce catalase is in dispute. The amount of catalase in milk as it comes from the udder varies at different stages of lactation. The cata- lase content is high during the colostral period and this condition usually continues for three weeks, although in exceptional cases it falls to the amount normal for milk by the fourth or fifth day after parturition. Near the end of lactation, when the milk has fallen to about a quart per day or less, the catalase again increases. Some MILK 39 observers report that no increase occurs duing cestum, but others state that when the cow is nervous and excitable the catalase is sometimes increased. Pronounced changes in the feed may affect the quantity of catalase. The first milk drawn at a milking contains less catalase than the end milk. When milk is separated, the greater portion of the catalase passes over into the cream. Skim milk, there- fore, has a very low catalase content. After milk has reached a certain degree of acidity (about 0.36 per cent.), the acid begins to exert an inhibitory influence on the activity of the catalase. Up to this point the catalytic activity is increased because the amount of catalase is increased by bacterial growth. In milk which has under- gone “sour curdling,” the catalase is paralyzed by the acid and is inactive. The catalytic activity may be re- stored to such milk by neutralizing it with lime water. When milk is exposed to a low temperature in winter or to prolonged refrigeration, the catalase is partially or completely destroyed. Catalase operates best at a tem- perature of 37° C. (98.6° F.). The lethal temperature is around 68° C, (154° F.), but varies within wide limits according to the source of the catalase. Heated milk may be reactivated, since catalase is a bacterial as well as an original ferment. (See catalase test on pages 287 to 294.) Reductase.—If a small quantity of methylene blue solution is added to milk, the mixture will be colored blue, but the blue color will disappear after a time because the methylene blue is reduced and converted into its leuco-base. This change is brought about by a ferment in the milk called reductase. If formalin is added to the methylene blue solution, forming what is known as Schar- 40 PRINCIPLES AND PRACTICE OF MILK HYGIENE dinger’s reagent, and a little of this solution is added to milk, the mixture will also be colored blue, but the color will disappear more rapidly. At first the difference in the time of reduction was attributed to the difference in the composition of the solution, but further research demonstrated the presence in milk of two different re- ducing agents. The ferment which reduces the methylene blue solution is cailed ‘“ M-reductase,” while the one which reduces the formalin-methylene blue solution has been named “ FM-reductase.” M-Reductase—This ferment is not secreted in the udder with the milk. It is generally regarded as of bacterial origin, although the opinion has been expressed (Burri and Kiirsteiner) that the cellular elements of milk, like all living protoplasm, have a reduction power and that the high reduction power of colostrum during the first day after parturition and of mastitis milk is due to the rich cellular content of these secretions. It has been well established, however, that the capacity of milk to reduce methylene blue increases with the number of bacteria. The different species of bacteria vary in their reduc- tion power. Reduction power appears to depend first upon the species, then upon the number of bacteria, and, finally, upon the media in which the organisms are grow- ing. 'The anaerobic organisms usually have a greater reduction power than the aerobes, while the facultative anaerobes act more powerfully in the absence of oxygen than when it is present. The colon bacilli belong to the facultative anaerobes of high reduction power. On the other hand, the reduction power of the lactic acid bacteria is weak. Different samples of fresh milk containing about the same number of bacteria may differ greatly in MILK 41 reduction power because of the difference in the species * of bacteria present. But, according to Barthel and O. Jensen, when milk is stored under suitable conditions, the relative proportion of the different species of bac- teria present is almost always changed in favor of the lactic acid organisms, so that in the case of market milk there is usually correspondence between the reduction time and the number of bacteria. The reduction power of a microdrganism is not con- stant, but depends upon the vitality of the organism; it will therefore decrease with the age of the organism and also when nutritive conditions are unfavorable. Hence, the reduction activity of milk rich in bacteria is relatively less than milk containing fewer bacteria. These factors render the reductase test less exact than the plate method for estimating the number of bacteria in market milk, but not for judging the “keeping qualities” of the milk, since the more vitally active the contained bacteria the more rapidly will the milk undergo bacterial decom- position. The reduction power of cream is greater than that of skim milk. The reduction power is greatest just be- fore curdling. In curdling, the ferment is precipitated with the curd. The ferment operates best at a tem- perature of 40 to 55° C. (104 to 131° F.) and is destroyed by a temperature of 70 to 80° C. (158 to Hie ¥.). F'M-Reductase—The knowledge concerning this ferment is not sufficiently definite at this time to be of any value in the practice of milk hygiene. FM-reductase is present in colostrum on the first day after parturition and is then absent from the udder secretion for two to three weeks, when it again appears in the milk. Schern 42 PRINCIPLES AND PRACTICE OF MILK HYGIENE therefore proposed the F M-reductase test as a means of determining whether or not a cow is “fresh.” FM- reductase is absent, or present only in very small quan- tity, in the first milk drawn at a milking, but it is always present in the end milk. After stasis of milk, it is absent. The reaction cannot be used for the detection of mastitis, because while reduction occurs rapidly in some cases, in others it occurs more slowly than in normal milk or may not occur at all. Antibodies or Immune Bodies.—Antibodies are sub- stances which are produced in the animal body to pro- tect it from the action of bacteria or their toxins. The term includes antitoxins, agglutinins, precipitins, op- sonins, lysins (amboceptors), complement, ete. Comple- ment is always present in the blood and the other kinds of antibodies are also contained in the normal serum in a non-specific form, but these antibodies do not appear in the blood in a specific form until after the body is invaded by pathogenic organisms or their toxins. It has been demonstrated that antitoxins, agglutinins, and opsonins pass over from the blood into the milk when the udder is in a normal condition. Bacterio-lysins are eliminated in the milk when the udder is affected with mastitis and during the colostral stage, but it is doubtful if they pass over from the blood into the milk under nor- mal conditions at other times. Complement is present in colostrum and also in milk when the udder is affected with mastitis. It may be present in normal milk for as long as twenty-six days after parturition, but after that time it is absent, according to some observers. The com- plement demonstration test has not come into general use for the detection of mastitis principally because cer- MILK 43 tain investigators have reported that complement is always present in milk from apparently normal cows. The quantity of antibodies in the milk compared with the quantity circulating in the blood is not definitely known. The question has been more extensively studied in connection with antitoxins than with the other anti- bodies, and it was found that the milk contains only one- thirtieth to one-fifteenth of the quantity of antitoxin circulating in the blood. Agglutinins may be present in the milk in the same quantity as in the blood, or in greater or less amount. The immunizing value of the milk has not been completely determined. It has been demonstrated that antibodies in milk ingested by suck- lings are absorbed through the intestines into the blood when the suckling and the animal from which the milk is obtained are of the same species. There is no direct evidence, however, that the antibodies are absorbed into the blood of the young animal when the milk is from a different species, as when a child ingests cow’s milk, al- though many observations have been made which indicate that antibodies are absorbed under such circumstances, if only to a limited extent. It would therefore appear that antibodies in cow’s milk are of more value to the calf than to a child ingesting such milk. The absorption of antibodies from the intestines is greatest during the first few days after birth and decreases with age. In older animals, the antibodies are split up by digestion like other proteids. Germicidal Action of Milk.—Milk from cows in normal condition always contains antibodies which destroy many of the bacteria commonly present in milk. The intensity and duration of this germicidal action varies with the temperature. If the milk is kept at 37° C. (98.6° F.), 44 PRINCIPLES AND PRACTICE OF MILK HYGIENE there will be a decided decrease in the number of bacteria for the first six hours after the milk is drawn from the cow; at 26 to 29° C. (79 to 84° F.) the decrease is less rapid, but continues for eight to ten hours, and at 15° C. (60° EF.) itis still further reduced in rate but continues for about twenty-four hours (Rosenau and McCoy). The effect of the same milk on-different species of bacteria is different, and the effect of different milks on the same species of bacteria also varies, showing that the antibodies are specific for certain species of bacteria. ‘The germic- idal power of milk is not capable of destroying all bac- teria which may gain access to milk during milking and the subsequent handling; hence precautions against bac- terial contamination together with proper cooling are none the less necessary. It is also incapable of always preventing the development of pathogenic bacteria. These organisms may enter the teat canal and milk cistern and even invade the gland alveoli. Heating milk for thirty minutes to 56° C. (133° F.) considerably weakens the germicidal property, and it is entirely destroyed by a temperature of 70° C. (158° F.), or above, for thirty minutes. Bacteria, therefore, grow more rapidly in heated milk than in fresh raw milk. The germicidal power of colostrum and of milk from cows affected with mastitis is greater than that of normal milk. Toxins.—It has been demonstrated that tetanus toxin may be eliminated in the milk of a cow affected with tetanus, and in sufficient quantity to kill mice fed with the milk (Miessner). ‘There is, therefore, reason to be- lieve that other bacterial toxins are also eliminated in the milk, although there is no direct proof. However, the quantity of toxin circulating in the blood is very small, even in severely infected animals, and only a MILK 45 minute quantity could be eliminated in the milk. When it is considered in addition that the milk secretion ceases in severely affected animals, the danger from toxins eliminated in the milk is very slight. Toxins may be produced by bacteria growing in milk after it is drawn from the udder. There is evidence to show that toxins are very readily absorbed through the gastro-intestinal mucous membrane of young animals. Toxins in milk from a different species are absorbed with much less facility than when the milk is from the same species. Diphtheria and tetanus toxins have been given to adult animals by the mouth in large quantities without any harmful effect, the toxins apparently being split up in the process of digestion like other proteids. These, how- ever, are soluble toxins (exogenous) which are more susceptible to chemicals and ferments than endotoxins. What may happen when the digestive processes are de- ranged, or when wounds are present in the mucous mem- brane, is not known. Milk from animals affected with rabies contains the virus of the disease, but such milk does not produce rabies when ingested if the mucous mem- brane of the digestive tract is intact and the gastric secre- tion is normal. Aggressins and other substances which inhibit the protective reaction of the body against the action of bac- teria and their toxins have also been demonstrated in milk. CLASSES OR GRADES OF MARKET MILK Until quite recently no effort was made to establish uniform grades or classes of milk. In some instances, the terms sanitary milk, hygienic milk, aérated milk, baby’s milk, nursery milk, etc., have been applied by dis- tributers to some of the milk sold by them, but these 46 PRINCIPLES AND PRACTICE OF MILK HYGIENE terms are very indefinite and have been frequently used indiscriminately. Since 1893, milk produced under the supervision of a medical milk commission has been sold under the name of certified milk, but the term has also been applied to milk which was not produced under these conditions. ‘The desirability of defining the special names used for milk, and the advantage to both the pro- ducer and consumer of grading or classifying market milk according to its hygienic quality, has long been recognized, but no definite steps were taken in the matter until 1907 when Melvin’ proposed that market milk be graded in three classes, as follows: Class 1. Certified Milk.—This may be briefly defined as milk produced in accordance with the requirements of the American Association of Medical Milk Commissions (see Appendix). Class 2. Inspected Milk.—This term should be limited to clean raw milk from healthy cows, as determined by the tuber- culin test and physical examination by a qualified veterinarian. The cows are to be fed, watered, housed, and milked under good conditions, but not necessarily equal to the conditions provided for Class 1. All persons who come in contact with the milk must exercise scrupulous cleanliness, and must not harbor the germs of typhoid fever, tuberculosis, diphtheria, and other in- fections liable to be conveyed by the milk. This milk is to be delivered in sterilized containers, and is to be kept at a tempera- ture not exceeding 50° F. until it reaches the consumer. It shall contain not more than 100,000 bacteria per cubic centimetre. Class 3. Pasteurized Milk.—Milk from the dairies not able to comply with the requirements specified for Classes 1 and 2 is to be pasteurized before being sold, and must be sold under the designation “ pasteurized milk.” Milk for pasteurization shall be kept at all times at a temperature not exceeding 60° F. while in transit from the dairy farm to the pasteurization plant, 124th Annual Report, U. S. Bureau of Animal Industry, pp. 179 to 182. MILK 47 and milk after pasteurization should be placed in sterilized con- tainers and delivered to the consumer at a temperature not exceeding 50° F. All milk of an unknown origin should be placed in Class 3 and subjected to clarification and pasteuriza- tion. No cow in any way unfit for the production of milk for use by man, as determined upon physical examination by an authorized veterinarian, and no cow suffering from a com- municable disease should be permitted to remain on any dairy farm on which milk of Class 3 is produced, except that cows which upon physical examination do not show physical signs of tuberculosis may be included in dairy herds supplying milk of this class. This milk is to be clarified and pasteurized at cen- tral pasteurization plants, which shall be under the personal supervision of an officer or officers of the health department. These pasteurizing plants may be provided either by private enterprise or by the municipality, and should be located within the city. A further attempt at classification was made in 1911 by a commission on milk standards appointed by the New York Milk Committee. This commission recommended that milk be graded in four classes, viz.: Class A, certi- fied milk or its equivalent; Class B, inspected milk; Class C, pasteurized milk, and Class D, milk not suitable for drinking purposes. A year later, however, the commis- sion presented a second report! in which the following classification was recommended: GRADE A Raw Milk.—Milk of this class shall come from cows free from disease as determined by tuberculin tests and physical examinations by a qualified veterimarian, and shall be produced and handled by employees free from disease as determined by 1 Reprint No. 141 from the Public Health Reports, Aug. 22, 1913. 48 PRINCIPLES AND PRACTICE OF MILK HYGIENE medical inspection of a qualified physician, under sanitary con- ditions such that the bacterial count shall not exceed 100,000 per cubic centimetre at the time of delivery to the consumer. It is recommended that dairies from which this supply is obtained shall score at least 80 on the United States Bureau of Animal Industry score card. Pasteurized Milk.—Milk of this class shall come from cows free from disease as determined by physical examinations by a qualified veterinarian and shall be produced and handled under sanitary conditions such that the bacterial count at no time ex- ceeds 200,000 per cubic centimetre. All milk of this class shall be pasteurized under official supervision, and the bacterial count shall not exceed 10,000 per cubic centimetre at the time of delivery to the consumer. It is recommended that dairies from which this supply is obtained shall score at least 65 on the United States Bureau of Animal Industry score card. The above represents only the minimum standards under which milk may be classified in Grade A. The commission recog- nizes, however, that there are grades of milk which are produced under unusually good conditions, in especially sanitary dairies, many of which are operated under the supervision of medical associations. Such milks clearly stand at the head of this grade. GRADE B Milk of this class shall come from cows free from disease as determined by physical examinations, of which one each year shall be by a qualified veterinarian, and shall be produced and handled under sanitary conditions such that the bacterial count at no time exceeds 1,000,000 per cubic centimetre. All milk of this class shall be pasteurized under official supervision, and the bacterial count shall not exceed 50,000 per cubic centimetre when delivered to the consumer. It is recommended that dairies producing Grade B milk should be scored and that the health departments or the con- trolling departments, whatever they may be, strive to bring these scores up as rapidly as possible. MILK 49 GRADE C Milk of this class shall come from cows free from disease as determined by physical examinations and shall include all milk that is preduced under conditions such that the bacterial count is in excess of 1,000,000 per cubic centimetre. All milk of this class shall be pasteurized, or heated to a higher temperature, and shall contain less than 50,000 bacteria per cubic centimetre when delivered to the consumer. Whenever any large city or community finds it necessary, on account of the length of haul or other peculiar conditions, to allow the sale of Grade C milk, its sale shall be surrounded by safeguards such as to insure the restriction of its use to cooking and manufacturing purposes. In 1917 the commission published a third report? in which the above-mentioned grades were again recom- mended with the same specifications for each grade ex- cept that the bacterial limit for Grade A, raw milk, was reduced from 100,000 to 10,000 bacteria per c.c. This is an extremely low bacterial limit for market milk to be used for general purposes and it is very doubtful if it can be adopted by any community without consider- ably reducing the supply of raw milk and increasing its cost to the consumer. Certified milk meets the demand for a milk of low bacterial content for special purposes, such as infant feeding, etc. 1 Public Health Reports, Vol. 32, No. 7, Feb. 16, 1917. CHAPTER IV BACTERIA OF MILK Un tess drawn under special conditions, which are not obtainable in dairy practice, milk always contains bacteria. Some of them come from the udder; others are derived from the cow’s skin, the dust of the fodder and litter, the milk vessels and utensils, the person and cloth- ing of the milker, etc., and enter the milk during the process of milking and in the subsequent handling of the milk. They are, under normal conditions, non-patho- genic organisms, and, since they are always present in milk, are called the common milk bacteria. Under cer- tain conditions, which are discussed in another chapter, milk contains also pathogenic bacteria. COMMON MILK BACTERIA Some of the non-pathogenic bacteria do not bring about any perceptible change in milk. Many of them, however, produce marked alterations, and it is because of their presence that milk is so extremely perishable or unstable. In growing in milk, these organisms split up certain constituents, notably the lactose and casein, into various products, some of which are capable of exerting an injurious effect upon persons drinking the milk, par- ticularly children and invalid adults. Certain of these changes, including the more harmful kinds, may be con- siderably advanced before they are indicated by any alter- ation in the appearance, odor, or taste of the milk. There- fore, while the common milk bacteria are in themselves harmless, and while their growth in milk to a limited 50 BACTERIA OF MILK dl extent is not attended with any appreciable injurious effects, their presence in large numbers is not desirable because it may be accompanied by harmful results. There are numerous species of these organisms. For facility of study as well as for practical purposes, it is convenient to group them according to the changes which they bring about in milk. Although some of the species which ferment lactose produce both acids and gases, and although a part of those which act principally upon the lactose also operate upon the casein in a lesser degree and vice versa, nevertheless by grouping the different species according to their dominant effect a very clear conception is obtained of the important changes produced in milk by the organisms of each group. Following this plan, the numerous species of common milk bacteria may be classified in the following groups: 1. Acid-forming Bacteria——These organisms split up the lactose in milk and form acids. The milk first acquires a sour odor and taste and later curdles. This is the most quickly apparent change which occurs in milk. ‘The acids combine with the calcium of the calcium caseinate, and the casein, being thus set free, is precipi- tated in the form of a smooth, white jelly-like curd, which may contain a few gas bubbles or furrows made by ascending bubbles. In the beginning, the curd is dry and is equal in size to the original volume of the milk, but later on it contracts and expresses a fluid or serum which holds in solution certain of the milk constituents. The time required for milk to sour and curdle depends upon the number and kind of acid-forming bacteria it contains and the temperature at which it is kept. On the average, about 0.45 per cent. acidity is necessary to bring about curdling. The acid-forming bacteria con- 52 PRINCIPLES AND PRACTICE OF MILK HYGIENE tinue to grow and to ferment lactose until the acidity reaches 0.8 per cent., but the growth of other bacteria stops when the acidity exceeds 0.2 per cent. The acid- forming bacteria, therefore, perform the very important service of inhibiting the growth of the more harmful bacteria. If their development is interfered with, the milk will undergo putrefaction instead of souring. Sour milk is net harmful to healthy adults; on the contrary, in certain forms (curds and whey, buttermilk, kefir, etc.) it is a regular article of diet, and milk contain- ing certain acid-forming bacteria is beneficial in some diseased conditions. But, nevertheless, milk in which the fermentation is not sufficiently advanced to cause coagu- lation or even to produce an appreciable sour taste may cause vomiting and indigestion in small children and in persons affected with catarrh of the stomach. The usual cause of the spontaneous curdling of milk is the Bacterium lactis acidi (Fig. 5), also called Strepto- coccus lacticus, which occurs as a coccus or as a short oval or pointed bacterium, arranged in pairs, frequently in short and sometimes in long chains, and forms on solid media very small, white, circular or lenticular colonies, many of them being situated below the surface. In addi- tion to the difference in form, variations occur in the ability to ferment lactose and in other biological char- acters. These are regarded by some bacteriologists as changes due to environment, while others consider them a sufficient basis for recognizing the existence of different varieties or species. In general, however, organisms of the Streptococcus lacticus type ferment lactose more rapidly than the other species of acid-forming bacteria, forming principally lactic acid, with little or no gas. The milk has a clean, sour taste, while the fluid expressed from BACTERIA OF MILK 53) the curd is clear. Being commonly concerned in the souring of milk and producing principally lactic acid, the organisms of this type are known as the true lactic acid bacteria. ‘The Streptococcus lacticus must not be confused with the mastitis streptococci (Fig. 6), which also ferment lactose and have other corresponding char- acteristics. The latter organisms grow in long, inter- twined chains, the individual members of which are rec- tangular cr oval in form, with the long axis at right Des rattchews OF Bacterium Latin coat Be ed De ceniittealistagreiie On Shae ne angles to the length of the chain. On agar, they form extremely minute, punctiform, brownish colonies. The Bacterium acidilactici (Hueppe), also called the Bacillus lactis aerogenes, is frequently concerned in the spontaneous souring of milk, usually in association with the Streptococcus lacticus. ‘This is a short, plump, non- motile bacterium which is closely related to the coli-aero- genes group of bacteria and may be regarded as the most active acid-forming member of that group. It grows upon the surface of solid media, forming thin, partially translucent, leaf-shaped colonies, or round semi-globular o4 PRINCIPLES AND PRACTICE OF MILK HYGIENE colonies. It ferments lactose more slowly and requires a higher temperature than the Streptococcus lacticus. Acetic acid is the principal product of the lactose fermen- tation, although lactic and succinic acids and gas are also formed. Gas bubbles are rather numerous in the curd and the fluid expressed from the latter is not always clear. The sour taste of the milk is frequently un- pleasant. The Bacterium acidilactici is regarded by some bacteriologists as a distinct species with strains showing differences resulting from environment and by others as the type of a number of species or varieties. The mastitis organisms, Bacillus Guillebeaw (a and b), and some of the bacteria which produce slimy or viscid milk are closely related forms. Several varieties of long, thin, rod-shaped organisms, of which the Bacterium bulgaricus is a type, also form acid from lactose, but they operate so slowly at the usual temperatures that they are not a factor in the ordinary souring of milk. They are chiefly of interest because of their use in the preparation of the oriental milks (mazun, kefir, yoghurt). The organisms of the Bacteriwm bul- garicus group are usually present in ensilage and those found in milk are no doubt derived directly or indirectly from this source. The temperature at which the milk is kept has an important influence upon the character of the lactose fermentation. In milk kept at 15 to 20° C. (59 to 68° -F.), the organisms of the Streptococcus lacticus type will grow much more rapidly than those of the Bacterium acidilacticitype. The Streptococcus lacticus grows quite well at 15° C. (59° F.) and continues to grow at 10° C. (50° F.), while the Bacterium acidi lactici grows bet- ter at higher temperatures and practically stops grow- » bac Fig. 8.—Colonies of Proteus vulgaris, natural size (Weigmann). BACTERIA OF MILK 55 ing at 15° C. (59° F.). Keeping milk at a tempera- ture of 15° C. (59° F.) or below, therefore, inhibits the least desirable type of lactose fermentation. The Bacil- lus bulgaricus requires a temperature of at least 25° C. (aie) The acid-forming bacteria are widely distributed, but according to Esten* the chief primary source of those of the Streptococcus lacticus type found in milk is the cow’s mouth. The organisms are present in the manger and on everything within reach of the cow’s mouth, also in the faeces. The acid-formers of the Bacterium acidi lactici type are derived from sugar-containing grain and roots like corn, beets, and carrots, especially when they are cut into small pieces, packed and fermented (ensilage) ; they are also contained in the faeces of cows (Weigmann). Milk vessels and utensils, and other things and places with which milk comes in contact become seeded with acid-forming bacteria when not properly cleaned and sterilized, and are usually the principal sources of con- tamination when these organisms are present in milk in excessive numbers. 2. Gas-forming Bacteria.—Included in this group are the bacteria which ferment the lactose in milk and form gases in addition to acids. They also decompose the proteids to some extent, especially the casein (Fig. 7). Most of them belong to the large coli-aerogenes group of organisms. ‘The milk is curdled in the form of a smooth, white, jelly-like curd, which is more or less per- meated with gas bubbles and is associated with some fluid. The aerogenes organisms form a greater quantity of acids and gases than the coli and they also form more 1 Bacterium Acidi Lactici and Its Sources,” Storr’s Agr. Expt. Sta. Bull. No. 59. 56 PRINCIPLES AND PRACTICE OF MILK HYGIENE lactic acid than the coli, but the latter are more active in proteid decomposition. Carbon dioxide, hydrogen, car- buretted hydrogen, and nitrogen are the gases produced, while the acids formed are lactic, acetic, and succinic. In the early stages of this change, the milk has a sweetish- sour refreshing taste and an odor that is not unpleasant, especially when the aerogenes bacteria are operating, but later the taste is unclean, while the odor is stable-like, and finally the taste becomes nauseating and salty and the odor is like that of decomposing manure and urine. Milk undergoing this form of fermentation and decomposition may prove harmful to persons drinking it, especially in- fants and adults with weak digestion. The principal representatives of this group of bac- teria are the Bacillus coli and the Bacillus aerogenes, also called Bacillus lactis aerogenes and Bacteriwm acidi lac- tict (Hueppe). The Bacillus coli is a short, thick, oval organism, which is motile, and which forms on solid media colonies which are usually flat, leaf-shaped and partially translucent, sometimes moist and globular. Some vari- eties render the milk alkaline and do not curdle it nor produce any other visible change; others peptonize the casein. Several varieties of coli are pathogenic, e.g., the bacilli of calf cholera, the Bacillus enteritidis (Gartner) and the Bacillus phlegmasia iiberis, which is one of the causes of parenchymatous mastitis according to Kitt. The Bacillus lactis aerogenes or Bacteriwm acidi lactict (Hueppe), described previously in connection with the acid-forming bacteria, may be regarded as a type of the aerogenes bacteria, of which there are a number of varieties. The optimum temperature of the coli-aerogenes bac- teria is 87° C. (98.6° F.), but they grow quite well at BACTERIA OF MILK 57 lower temperatures down to 20° C. (68° F.). They do not grow as well as the Streptococcus lacticus between 15 and 20° C. (59 and 68° F.), and at lower tempera- tures the difference is still greater. These organisms are normal inhabitants of the in- testines of the cow and consequently are hardly ever en- tirely absent from milk. They are present in water pol- luted by drainage from barnyards, manure heaps and cesspools, and also on field crops, especially roots grown on manured ground. Their presence in milk in any considerable number indicates that it has been contami- nated with manure or with polluted water. Milk also contains anaerobic bacteria which ferment lactose and its salts, forming gas in large quantity and producing strong-smelling acids like butyric, valerianic and propionic. These organisms are present ordinarily in small number and their development is usually pre- vented by the acid-forming bacteria. When they grow in milk in large numbers, a curd containing many gas bubbles is formed. The milk has the odor of the acid produced and frequently an odor of putrefaction also. Because of the latter condition, these organisms are re- garded as putrefactive bacteria. The best known are those which produce butyric acid and are consequently called butyric acid bacteria. They are very large spore- forming bacilli which live in cultivated soil in symbiosis with the peptonizing bacteria. They are usually present in the spore-forming stage on the products of the field. Morphologically, they are distinguished from the other spore-forming milk bacteria by a change in form during spore formation, becoming shuttle-shape, drum-stick- shape, etc. Ayers and Johnson found gas-forming bacteria in 58 PRINCIPLES AND PRACTICE OF MILK HYGIENE milk which were not members of the coli-aerogenes group but which were apparently spore-formers, having sur- vived a temperature of 93.3° C. (200° F.) for thirty minutes." 3. Peptonizing or Casease Bacteria.—The bacteria of this group are also known as liquefiers and are the cause of decay and putrefaction in general. They secrete two enzymes or ferments which attack the proteids of milk, especially the casein. One is a rennet-like ferment which acts upon the calcium caseinate in the same manner as rennet, splitting it up into calcium paracaseinate and a substance called whey-proteid. The calcium para- caseinate being insoluble, it is precipitated and forms a curd. The whey-proteid remains in solution in the whey, hence the name. The other enzyme is casease, a proteo- lytic ferment resembling trypsin, which digests the pro- teids in the curd and whey, splitting them up into soluble compounds like albumoses and peptones (peptonization) and then again into simpler compounds like amino-acids and ammonium bases (decomposition). The two fer- ments are produced in varying proportions by different species of bacteria. When the rennet-like ferment pre- dominates a firm white curd is formed and is slowly digested. There is more or less fluid (whey) present. As digestion proceeds, the curd gradually disappears and is replaced by a turbid fluid. The surface of the curd in contact with the fluid has a rough or fuzzy appearance. When the proteolytic ferment (casease) is present in greatest quantity, the curd is soft, flocculent and “mushy,” or coagulation does not occur at all, while peptonization takes place rapidly. In the earlier stages 1B. A. I. Bulletin No. 161, pp. 47 and 48. BACTERIA OF MILK 59 of this type of decomposition, the milk acquires a bitter taste (peptones) and later the taste and odor are foul and unpleasant. Some of the decomposition products are capable of exerting an injurious effect upon persons drinking the milk. Nausea and vomiting may occur, even in adults, when the taste is only bitter and before it has become decidedly foul. ‘The reaction of the milk is usually alkaline, but some of the peptonizers are acid- formers and curdle milk by souring it. Included in this group are certain of the cocci which appear to be constantly present in the lower parts of the cow’s udder and are consequently called udder cocci. These organisms are to be found regularly in milk when it comes from the udder, especially in the fore milk. They are present in greater proportion in milk produced under good conditions than in ordinary milk. There are many varieties or species of these organisms which differ principally in their fermentative properties and in the color of their colonies. In milk hygiene, it is desirable to divide them into peptonizers and non-peptonizers. Part of the peptonizers first curdle milk and then digest the curd; others bring about digestion without previous cur- dling. Some of the organisms which curdle the milk do so by means of a rennet-like ferment; the others by means of acid resulting from fermentation of the lactose (acid peptonizers). The non-peptonizers are practically inert, producing no apparent change in milk. On agar plates, the udder cocci form small, irregularly round colonies which are usually white. The colonies of Staphylococcus pyogenes albus vary from white to cream color, while those of Staphylococcus pyogenes aureus are orange- yellow. The latter two organisms are peptonizers and also form lactic acid. The ordinary udder cocci and 60 PRINCIPLES AND PRACTICE OF MILK HYGIENE Staphylococcus pyogenes albus and aureus are similar in so many respects that all are regarded by some bac- teriologists as different varieties of the same species. The optimum temperature for the udder cocci is 35 to 37° C. (95 to 98.6° F.), but they grow well at much lower temperatures, development continuing down to freezing. The peptonizing action is exerted at these low temperatures. Many of the peptonizers are spore-forming bacteria. The most common representatives of this division are the hay bacillus (Bacillus subtilis) and the potato bacillus (Bacillus mesentericus vulgatus). ‘They belong to a large group of organisms which are very numerous in cultivated soil and are:consequently found on all products of the soil, especially hay, straw, roots, etc. They are large rod-shaped bacteria with rounded ends. 'The spores form in the middle or end of the organism without chang- ing its shape. On agar plates these bacteria form dry, thin, superficial skin-like colonies, with irregular borders. The colonies have a tendency to extend over the surface of the media and are consequently called “ spreaders.” These organisms are very numerous in the dust of hay and other dry fodder, also in straw, and they may get into the milk in large numbers if the fodder or litter is brought into the stable and distributed a short time before milking, or if dust from hay or other dry fodder is per- mitted to sift down into the stable through cracks in the ceiling. When a cow lies upon bedding or upon loose soil, these bacteria enter the folds and creases of the skin and become attached to the hair, and when the cow is milked those upon the udder, flanks and surrounding parts are dislodged and may fall into the milk pail. These organisms are especially numerous on the hair BACTERIA OF MILK 61 and skin of cows at pasture. The manure does not con- tain very many and few are carried into milk on this substance (Weigmann). The hay and potato bacilli grow best at 23 to 37° C. (73 to 99.6° F.), but will de- velop at any temperature between 10 and 45° C. (50 to 113° F.). The spores are very resistant to heat and will survive several hours boiling. Other peptonizers include the bacteria of the proteus group of putrefactive organisms, which are often present in milk, although more frequently found in water (Fig. 8). They are long, thin bacilli which grow in colonies of various forms. The most common representative of these organisms is the Bacillus proteus vulgaris, which grows in colonies with branches or ray-like projections. They get into the milk principally through the water used to wash the milk vessels and utensils. The Bacillus proteus vulgaris grows best at about 25° C. (77° F.) 4, Alkali-forming Bacteria—Some of the bacteria commonly found in milk render the milk alkaline without producing any change for a time in its appearance, taste, or odor. When the alkalinity has attained a certain degree, the fat is saponified and the neutral calcium caseinate compound becomes basic, in consequence of which the milk is changed to a yellow, translucent, whey- like fluid (Jensen). Within the ordinary life of milk, however, the bacteria of this group are practically without effect. Usually they get into the milk in the same man- ner as hay bacilli (page 60), their source being the soil, but occasionally they are derived from the feces (Rogers). 5. Inert Bacteria——A large number of the common milk bacteria produce no change in the appearance, odor, taste, or reaction of milk and are consequently said to 62 PRINCIPLES AND PRACTICE OF MILK HYGIENE be inert. Many bacteria belong to this group, which in- cludes some of the udder cocci. Many of the most im- portant pathogenic organisms are also inert in so far as their effect on milk is concerned, notably the tubercle bacillus, the bacillus of typhoid fever, paracoli or para- typhus bacilli, and the diphtheria bacillus. The presence of these harmful organisms is not indicated by any ap- parent change in the milk. VARIATIONS IN NUMBER AND KIND OF BACTERIA Different samples of market milk may show the greatest differences in the number and kind of bacteria present. One sample may contain much fewer than 1000 bacteria per c.c. and another may contain four or five million and even more. In one sample, the bacteria may be largely of the inert forms and in another the bacteria of the gas-forming group may predominate. Market milk containing not more than 100,000 bacteria per c.c. is considered of good quality. The limit for certified milk is 10,000 bacteria per c.c. The kind or species of the bacteria must be considered as well as the number. Generally, the smaller the num- ber of bacteria present the better the milk, but there are exceptions to this rule. A few pathogenic organisms would be more harmful than a much larger number of the common milk bacteria. Between the different groups of the latter there are also important differences. Milk containing a rather large number of bacteria the greater proportion of which belong to the inert or lactic acid groups is less objectionable than milk containing a smaller number of bacteria with the greater proportion belonging to the gas-forming or peptonizing groups. On the other hand, while milk containing a large percentage BACTERIA OF MILK 63 of peptonizing bacteria is not objectionable when the total number of bacteria is small, it is always objection- able when the bacterial count is high. The number of bacteria present in market milk de- pends upon (1) the original contamination, (2) the temperature at which the milk has been kept, and (3) the age of the milk, z.e., the time which has elapsed since the milk was drawn from the cow. 1. By original contamination is meant the bacteria which get into the milk during milking and the subse- quent handling of the milk. The extent of this depends upon the cleanliness and health of the cows, stable prac- tices, method of milking, cleanliness of the milk vessels and utensils, etc. 2. The temperature at which milk is kept affects not only the total number of bacteria but also influences the relative rate of increase of the different kinds or species. As a rule, the higher the temperature the more rapidly the bacteria multiply. For example, Conn found that when fresh milk contained 6525 bacteria per cc., after 25 hours at 10° C. (50° F.) it contained 6425 bac- teria per c.c., while after 25 hours at 21° C. (70° F.) it contained 6,275,000 bacteria per c.c. When milk is promptly cooled to 10° C. (50° F.) and held at that temperature, little or no increase of bacteria will occur for twenty-four to thirty-six hours, and even at 15° C. (59° F.) the increase will not be very great. At temperatures above 20° C. (68° F.), however, the bacteria increase very rapidly. As stated above, the temperature affects not only the number of bacteria but also the relative development of the different species. In other words, it determines the type of fermentation or decomposition which the milk 64 PRINCIPLES AND PRACTICE OF MILK HYGIENE will undergo with age. Most species of bacteria thrive best at about body temperature (37 to 38° C., 98.6 to 100.4° F.), but at lower temperatures some multiply more rapidly than others. At temperatures below 15° C. (59° F.), and especially below 10° C. (50° F.), the or- ganisms of the peptonizing group develop more rapidly than any of the other common milk bacteria. At 15 to 20° C. (59 to 68° F.), the true lactic acid bacteria in- crease faster than any of the others. At temperatures above 20° C. (68° F.), the acid-forming bacteria may continue to multiply more rapidly than the others, but the gas-formers are more likely to increase most rapidly. The higher temperatures are also favorable to the de- velopment of pathogenic organisms. 3. The age of milk has considerable influence on the number of bacteria. 'The longer the period which has elapsed since the milk was drawn from the cow the more time afforded for the multiplication of the bacteria in- cluded in the original contamination. (The method of determining the number of bacteria is described on pages 260 to 272.) Proportion of Different Groups of Bacteria.—The kind or species of bacteria included in the original con- tamination, and the relative proportion in which the different groups are represented, will vary with the con- ditions under which the milk is produced. In milk pro- duced under good conditions and examined shortly after it was drawn from the cows, Conn found that the greater portion of the bacteria are udder cocci, including both peptonizers and the inert variety. Usually 1 or 2 per cent., sometimes more, are lactic acid bacteria. A few gas-producing bacteria and hay and potato bacilli are likely to be present, but they should never be numerous. BACTERIA OF MILK 65 The kind of bacteria which will predominate in milk of this kind when it reaches the consumer will depend upon the temperature at which it is kept (see above). The fermentation test offers a rapid and convenient method of determining the kind of bacteria which predominates in a sample of milk (see page 278). A large percentage of the bacteria present in market milk belongs to the inert group. This is shown by the following table compiled from examinations reported by Ayers and Johnson?: No. samples Average Percent. Percent. Percent. Percent. Percent. examined. number bac- peptonizing. Alkali- inert. Acid, coag- Acid, non- teria per c.c. forming. ulating. coagulating. 12 32,950,000 17.31 6.47 29.381 36.17 10.71 17 3,451,000 14.10 19.66 43.51 12.98 9.74 24,700 12.81 3.33 43.13 33.85 6.85 1B. A. I. Bull. 161, pp.20-27. CHAPTER V MILK DEFECTS In addition to the changes in milk caused by the common milk bacteria and those occurring in the course of diseases of the cow, there are certain alterations in consistency, odor, taste, and color which are known as milk defects. Some of these defects make the milk re- volting, even nauseating, while a few render it harmful. They may be divided into two groups (a) those which are present when the milk is drawn from the udder and (b) those which appear shortly afterward. (a) Milk Defects which are Present in Milk when it Comes from the Udder.—The most important of these are named below, together with the causes, the latter being given because they indicate the measures to be taken for the correction or removal of the defects. 1. Cow-like or Salty, Cow-like Taste —The milk has a strong cow-like taste or a salty, cow-like taste, is of a gray color and may have the appearance of soapy water. This may be due to several causes. Milk from cows in the last stages of lactation has a mild, cow-like taste which is attributed to the relaxation of the gland tissue and fil- tration of blood serum between the epithelial cells of the alveoli. The cow-like taste also occurs when the cow has been incompletely milked at the previous milking, and it is claimed that the first few streams of every milk- ing have a similar taste. In these cases it is thought that the abnormal taste is due to bacteria which enter the teat canal. Certain staphylococci and streptococci and some 66 MILK DEFECTS 67 bacteria of the coli-aerogenes group give milk a cow-like, salty taste (Weigmann). 2. “ Fishy ” Milk.—Milk from cows near the end of lactation may have a “ fishy ” taste. This defect is be- lieved to result also from feeding fish meal and from graz- ing cows on marshes subject to overflow with salt water; but cows have been fed on large quantities of fish meal without affecting the taste of the milk or butter. In one instance, the milk of one cow in a herd had such a pro- nounced “fishy ” taste that it tainted the milk from the entire herd, although this cow was fed and stabled in exactly the same manner as the others. The cause in this case could not be determined. Milk may acquire a “fishy ” taste from milk vessels which are rusted and also from those which have not been rinsed clean of the soap powder used in washing them. 3. Rancid Milk.—A rancid odor and taste in milk as it comes from the udder may be due to the same condi- tions which give milk a cow-like taste. A rancid odor and taste may appear a short time after the milk is drawn from the udder as a result of the growth of butyric acid bacteria (page 57). On several occasions an unidenti- fied biscuit-shaped organism, growing in pairs, with the flat sides toward each other, has been found to be the cause of a rancid odor and taste. 4. Slow-creaming Milk.—The milk is thicker and more viscous than usual; the cream separates slowly and in less quantity than normal, sours slowly and does not “butter” readily. This defect has been observed in the milk from cows near the end of lactation and in milk from cows fed on beets, carrots, and turnips. Certain species of bacteria greatly increase the viscosity of milk, pro- 68 PRINCIPLES AND PRACTICE OF MILK HYGIENE ducing what is known as viscid, “ropy,” or “ stringy ” milk (page 69). 5. Premature curdling may occur in connection with disturbances of digestion, udder diseases, advanced preg- nancy, overexertion and feeding sour brewers’ grains and distillery slop; it may also result from the develop- ment of excessive numbers of the acid-forming and peptonizing udder cocci as a consequence of incomplete milking. In the latter case, sodium bicarbonate or sali- cylic acid internally is recommended. 6. “ Gritty” or “ Sandy” Milk.—Small granular particles, concrements of calcium and magnesium phos- phate, occur in milk when defects exist in the epithelium of the alveoli of the udder which permit the passage of the salts of the blood; also when salts are present in the blood in excessive quantity as a result of the feeding of substances containing a high percentage of mineral mat- ter (Weigmann). These granules may be increased in size by the adhesion of mucus, epithelial cells, salts, etc., and form milk stones or udder stones (calculi), which may make milking difficult or painful. The calculi are of various shapes and sizes and may be as large as a bean. “ Bloody ” milk, the “ flaky” milk occurring in mas- titis and the other changes associated with disease of the udder and other pathological conditions are considered in the chapter on the “ Influence of Disease Upon Milk.” For other defects, see also the remarks under odor and taste (page 28). (6) Milk Defects which Appear after the Milk i is Drawn from the Udder.—The greater part of these defects are caused by certain species of bacteria, yeasts and fungi which grow well at low temperatures. Spring- houses, cooling-rooms and other dark, damp places fur- MILK DEFECTS 69 nish an environment favorable to their development. Measures for the correction of these defects must be based upon the source of the organisms concerned. 1. Bitter Milk—Several species of bacteria, yeasts and fungi have been isolated at different times from bitter milk. In some instances the organisms responsible for the bitter taste were found in the udder. Milk may ac- quire a bitter taste from the action of the organisms belonging to the peptonizing and gas-forming groups of the common milk bacteria. This is especially true of heated milk, in which the spores of the soil bacteria (hay and potato bacilli )survive. The occurrence of a bitter taste in milk is often associated with the feeding of cer- tain substances, notably mouldy or decomposed fodder, beet and turnip leaves, and raw potatoes; also vetch, wild mustard and other cruciferous plants, leek, dog-fennel, tansy, etc. The use of mouldy or decomposed straw for bedding is accompanied by the same effect. It is believed that the bitter taste is caused by organisms which are present on these substances and which enter the milk after it is drawn from the udder, and it is recommended, therefore, that these feeds be given after milking, except- ing, of course, those which are mouldy or decomposed. Another theory is that the taste is due to a bitter sub- stance which is ingested with the food and eliminated through the udder. If milk is stored in rusted vessels until a certain degree of acidity develops, it acquires a bitter, astringent taste, due to formation of iron lactate or acetate. Milk may also have a bitter taste just before parturition and near the end of lactation. 2. Viscid, “ Ropy,’ or “ Stringy”’ Milk.—The milk is thick and viscid and when it is poured from one vessel to another strings are formed; it may also be drawn out 70 PRINCIPLES AND PRACTICE OF MILK HYGIENE into long strings with a rod or stick. The bacteria which cause this defect are frequently introduced into the milk by the water used to wash the milk vessels and utensils. Milk-houses, storage tanks, etc., may be infected by the same means. Water from streams and shallow wells receiving surface drainage, also from springs receiving surface or subsurface drainage, is especially likely to contain the organisms. They are also to be found on vegetation growing in low, damp places and on straw stored in a damp condition. In Sweden “ stringy ” milk is prepared artificially and is a popular article of food (tatmjolk), while, in Holland, Edam cheese is made from “ stringy ” milk produced by a certain organism. 3. “ Soapy”’ Taste—Milk may acquire a “ soapy ” taste from the action of bacteria which attack the proteids and fat of milk. Several species of these organisms have been found on straw and fodder. 4. Failure to Sour and “ Butter.’—Milk may not sour and cream may not sour and “ butter ” at all or only very slowly. This defect may be due to a deficiency in acid-forming bacteria or to an excess of peptonizers. In the latter case, the milk or cream usually has a bitter taste; occasionally a “ soapy ” taste. Alkali-forming bac- teria, butyric acid bacteria, some of the organisms of the coli-aerogenes group and certain yeasts and fungi may also delay or prevent souring and “ buttering.” In some cases the cream foams when churned, in consequence of the formation of gas. This defect is especially liable to occur when cows are pastured on low, wet land; also when the leaves of roots (beets, etc.), are fed, and in cold, wet weather. Cream from the milk of cows near the end of lactation will not “ butter” sometimes because of the alkalinity of the secretion. MILK DEFECTS 71 5. Stable-like, turnip-like, and beet-like tastes, and a burnt or malt-like taste and odor are each caused by cer- tain species of bacteria. 6. Blue Milk.—The Bacillus cyanogenus, also called the Bacterium syncyaneum, produces a grayish color on the surface of milk and, when the milk is sour, blue spots, which may become confluent. There are several other species of bacteria which produce a blue color in milk. 7. Red Milk.—Red spots or a diffuse red color on the surface are produced by the Bacillus prodigiosus, also by Sarcina rosacea and several other species of organisms. The Bacteriwm lactis erythrogenis curdles milk, then dissolves the curd and colors the fluid diffusely red. 8. Yellow- or orange-colored spots are produced usually by the Bacillus synaanthus; also by the Sarcina lutea, Sarcina flava and the Bacterium fulvwm. 9. A yellowish-green discoloration is produced by the Bacillus pyocyaneus. 10. Greenish-yellow spots and diffuse discoloration may occur in sour milk as a result of the growth of the Bacillus fluorescens. 11. Violet-colored spots are produced by the Bacillus violaceus, Bacterium janthinum, Bacillus lividus and Bacterium amethystinus. In some cases, although very rarely, these pigment- forming bacteria are present in the udder. Usually, they enter the milk after it is drawn from the udder. They can generally be excluded by sterilizing the milk vessels and cleaning and disinfecting the places where the milk is stored; sunning it also if possible. Sometimes it will also be necessary to clean and disinfect the stable and to see that the cows are thoroughly cleaned before milking. CHAPTER VI INFLUENCE OF DISEASE UPON MILK Man is susceptible to several of the specific infectious diseases of cattle viz: tuberculosis, aphthous fever or foot and mouth disease, cowpox, anthrax, rabies, and actinomycosis. Furthermore, mastitis, calf cholera, acute croupous and hemorrhagic enteritis (paracoli infection), septic metritis, and many suppurative conditions in cattle are caused by bacteria which are pathogenic for man. In certain non-bacterial affections, such as gastro-intestinal catarrh, the milk sometimes becomes unpalatable and, when ingested, may cause irritation of the gastro-intes- tinal tract, especially in children. The study of the conditions under which disease-pro- ducing organisms enter the milk and the effect of disease upon the milk secretion is one of the important divisions of milk hygiene. Bacteria or virus may be carried by the blood to the udder and be eliminated with the milk, or they may be excreted through one of the other normal open channels or discharged from wounds and enter the milk after it is drawn from the udder. The first method is called direct infection and the latter secondary infec- tion. ‘There is no doubt that bacteria circulating in the blood may pass over into the milk when the tissue sepa- rating the udder alveoli and tubules from the capillaries is broken down by disease. Some investigators are of the opinion that this may also occur when the udder tissue is intact, but this view is disputed by others. When bacteria invade the udder through the teat canal, as 72 INFLUENCE OF DISEASE UPON MILK 73 occurs in the non-tuberculous forms of mastitis, they are, of course, always eliminated in the milk. In considering the influence of disease of the cow on market milk, the effect of dilution must not be overlooked. Milk from a diseased cow may be injurious when ingested by itself, but when it is mixed with the milk from a num- ber of other cows in a normal condition it may be so diluted as to render it harmless. The character of the mixed milk in this respect will depend partly upon the proportion of diseased cows to those in health, partly _ upon the ability of the organism concerned to grow in milk, and the temperature at which the milk is kept. The diseased conditions affecting milch cows which are of importance in milk hygiene will now be considered separately. I. DiIsEAsEs oF CATTLE TRANSMISSIBLE TO MAN THroucH MILK TUBERCULOSIS In milk hygiene there are four points to be considered in connection with tuberculosis: (1) The frequency of tubercle bacilli in market milk, (2) the virulence for man of tubercle bacilli from cattle, (3) the conditions under which milk is infected with tubercle bacilli by tuberculous cows, and (4) how can contamination of market milk with tubercle bacilli be prevented. 1, The Frequency of Tubercle Bacilli in Market Milk.— In a number of cities in this country and abroad, samples of market milk have been collected and examined for tubercle bacilli. Anderson’ examined 233 samples in Washington in 1906 and found tubercle bacilli in 6.72 1 U.S. Hygienic Lab. Bull., No. 56, pp. 167-197. 74 PRINCIPLES AND PRACTICE OF MILK HYGIENE percent. In Philadelphia, in 1908, Campbell ? examined 130 samples of raw milk and found tubercle bacilli in 13.8 per cent.; twelve samples of milk sold as “ pasteur- ized ” were also examined by him and one sample, or 8.3 per cent., contained virulent tubercle bacilli. Hess * found tubercle bacilli in 16 per cent. of the samples he examined in New York in 1909, and of 144 samples ex- amined by 'Tonney in Chicago in 1910 10.5 per cent. were infected with tubercle bacilli. In Germany, from 16.5 to 27.1 per cent. of the samples of market milk examined in various cities contained tubercle bacilli; in England, 10 to 25 per cent.; in Paris, 20 per cent., and in Copen- hagen, 4 per cent.* Another evidence of the frequency of tubercle bacilli in milk is the general virulence of sep- arator milk from creameries. This milk has been found to be such a great factor in the dissemination of tubercu- losis among calves and hogs that several states, among them Pennsylvania, have passed laws requiring such milk to be pasteurized before it is removed from the creamery to be fed to cattle or swine. There are no statistics which show definitely the ex- tent to which tuberculosis exists among dairy cattle in the United States. The disease is found in less than 1 per cent. of the cattle slaughtered for meat under Federal inspection, but the greater proportion of these are beef cattle and many of them are of young age, a period when tuberculosis is not as frequently found as in later life. The proportion of dairy cows affected with tuberculosis is not known. The per cent. of infected animals varies 2 26th Annual Report, B. A. L., pp. 175-177. 3 The Incidence of Tubercle Bacilli in New York City Milk, Jour. Am. Med. Assoc., No. 13, Vol. 52. * Rievel, Milchkunde, pp. 99-100. INFLUENCE OF DISEASE UPON MILK 75 greatly in different localities and in different herds in the same section. The proportion of animals reacting to the tuberculin test ranges from none in herds which have been subjected to annual tests for several years to 30 per cent. and over in herds in which no effort has been made to control the disease. 2. Virulence for Man of Tubercle Bacilli from Cattle.— —Until 1901 it was very generally accepted that tuber- culosis in man and animals was the same disease, although Theobold Smith, in 1896, and, subsequently, others, pointed out important differences in virulence, morphol- ogy, and cultural characteristics between bacilli from human and bovine sources. In 1901 Koch announced that tuberculosis of cattle was so rarely transmitted to man that it could practically be disregarded in formulat- ing plans to protect man against the disease. This an- nouncement was based on the failure of Koch and Schiitz to infect calves and other animals with tuberculous ma- terial from man, and upon post-mortem statistics col- lected by them of a number of cases of tuberculosis in man which happened to include only a small proportion of in- dividuals showing primary lesions in the digestive tract or attached lymph glands. Koch’s announcement made a pronounced impression upon the general public, al- though his experiments were not original nor were his re- sults undisputed. ‘Theobold Smith, Frothingham, and Dinwiddie in this country, and Piitz, Gaiser, Nocard, McFadyean, Thomasson, Chauveau, Klebbs, Kitt, Bol- linger, and Crookshank abroad, had previously at- tempted to infect cattle with tuberculous material from man and had succeeded in doing so, although they found that these animals were less susceptible to human tuber- culous material than to that from bovine sources. Since 76 PRINCIPLES AND PRACTICE OF MILK HYGIENE Koch’s announcement was made, some thirty-five or forty investigators in different parts of the world have at- tempted to transmit human tuberculosis to cattle and all have succeeded but one. As to the other point upon which Koch based his views, the frequency of primary tuberculosis of the digestive tract or attached lymph glands, we learn from the in- vestigations of others that, while this form of tuberculosis is rare in adults, the proportion of cases found in children by different investigators is extremely variable, ranging from 14 to 87.8 per cent. ; consequently the statistics col- lected by any one or two men cannot be accepted as representing the percentage of cases in which the lesions are primary in the digestive tract or attached lymph glands. Evidence has also been produced by the experi- ments of Mohler, Ravenel, Calmette, and others that tubercle bacilli may be introduced through the digestive tract and primary lesions established in the lungs or thoracic lymph glands without producing any lesions in the intestines or mesenteric lymph glands. Koch’s views were not accepted by many of those who had made a special study of tuberculosis, and his an- nouncement instigated a vast amount of research work. Commissions were appointed by the British and German governments to investigate the relation of bovine to human tuberculosis, and other official bodies, and many individuals also took up the study of the subject. Koch contended that it could be assumed that the infecting material had been ingested with the food only when primary lesions were found in the digestive tract or its attached lymph glands, and that only those cases in which tubercle bacilli of the bovine type were demonstrated in the lesions could be regarded as having been infected by INFLUENCE OF DISEASE UPON MILK 77 the products (meat and milk) of tuberculous animals. The investigations were therefore largely directed along these lines. The present views of those who have studied the subject are fairly represented by the conclusions reached by the British commission and published in 1911 after a careful and thorough inquiry extending over ten years. These conclusions are as follows: “There can be no doubt that a considerable propor- tion of the tuberculosis affecting children is of bovine origin, more particularly that which affects primarily the abdominal organs and the cervical glands. ‘And, fur- ther, there can be no doubt that primary abdominal tuber- culosis as well as tuberculosis of the cervical glands is commonly due to ingestion of tuberculous infective material.” One hundred and eight cases of human tuber- culosis other than lupus were examined by the Commis- sion and bacilli of the bovine type were found in twenty- four, or 22 per cent. The latter included sixteen cases of primary abdominal tuberculosis, three of tuberculosis of the cervical lymph glands, two of pulmonary tubercu- losis, two of tuberculosis of the bronchial lymph glands and one of joint tuberculosis. Bacilli of the bovine type were found in nearly half of the fatal cases of primary abdominal tuberculosis. | The German commission made a study of fifty-six different cultures obtained from cases of tuberculosis in man and found six, or more than 10 per cent., to be of the bovine type. Park and Krumwiede ® determined the type of bacilli present in 487 cases of tuberculosis in man and collected from the literature the records of 1033 cases in which the 5 Journal Med. Research, pp. 109-114, vol. 27. 78 PRINCIPLES AND PRACTICE OF MILK HYGIENE type of the organism was determined by others, a total of 1511 cases. There were 955 cases in individuals over 16 years of age, 177 in children between 5 and 16 years, and 368 in children under 5. Tubercle bacilli of the bovine type were found in 35 per cent. of the cases in children between the ages of 5 and 16, and in 26 per cent. of the cases in children under 5. In addition to these, there were eleven cases in which both types of bacilli were found. It is usually difficult to discover the source of infec- tion in cases of tuberculosis in man because the disease does not become apparent for a long time after exposure to infection has occurred. Nevertheless, there are a number of cases recorded of tuberculosis in children and adults using milk from tuberculous cows for which no other source of infection could be found.® Regarding the evidence in these cases as generally incomplete, Koch, in 1902, suggested that a search be made for cows in which tuberculosis of the udder could be positively diagnosed and, when such cases were found, that it be ascertained how long the disease had existed, who consumed the milk or its products, whether the milk was used raw or cooked, and if the persons who used the milk or its products were infected with tuberculosis. Between 1905 and 1909 Weber and Ungerman’ found in Germany 69 cases of udder tuberculosis concerning which the information de- sired could be obtained. Three hundred and sixty per- sons, including 151 children, used milk from these cows. Two boys were affected with tuberculosis of the cervical lymph glands in which bacilli of the bovine type were 6 Rievel, Milchkunde, pp. 107-108. 7 Cited by Ostertag, Zeitschr. fiir Fleisch u. Milchhygiene, pp. 26 and 27, No. 2, vol. xxiii; p. 123, No. 6, vol. xxiv. INFLUENCE OF DISEASE UPON MILK 79 demonstrated. Six other children and one adult were found with swelling of the cervical lymph glands, four children and one adult showed symptoms indicative of abdominal tuberculosis and one child suffered from scrofula, but in these cases no material could be obtained for bacteriological examination. Forty-one other persons showed various symptoms of disease, but tubercle bacilli could be demonstrated in only 4, and these bacilli were of the human type. The other 304 individuals who had used milk from the tuberculous udders, or products made from such milk, showed no symptoms of disturbed health in 1910. Subsequently, one of these, a girl, developed a peritonitis for which the infected milk was probably re- sponsible. While in some instances the milk was heated, mixed with milk from apparently healthy cows, or only a small quantity was used in tea or coffee, nevertheless the results of this investigation would indicate that a con- siderable amount of infectious material and favorable accessory conditions are required to infect man with bovine tuberculosis. But, as Weber himself has pointed out, it must be remembered that it is not known positively that the individuals manifesting symptoms suspicious of cervical lymph gland and abdominal tuberculosis were not actually infected, nor how many of the apparently healthy persons concerned were affected with lat- ent tuberculosis which may later, under some debilitat- ing influence, become active and progress to a fatal termination. Furthermore, Weber’s observations are not confirmed by others who have studied the frequency of the trans- mission of bovine infection to man by milk. A comparison of the occurrence of tuberculosis in breast-fed children 80 PRINCIPLES AND PRACTICE OF MILK HYGIENE with the frequency of the disease in children receiving cow’s milk was made by Sobotta. Of 80 exclusively breast-fed children, 17.5 per cent. were infected with tuberculosis; of 57 children receiving cow’s milk in addi- tion to mother’s milk, 35.1 per cent. were infected, and of 30 fed exclusively on cow’s milk 41 per cent. became tuberculous.* Mitchell ® examined 72 cases of cervical gland tuberculosis in the Children’s Hospital in Edin- burgh and found tubercle bacilli of the bovine type in 65, or 90 per cent. These children came from districts in which the cattle are extensively infected with tuber- culosis and most of them had been nourished on cow’s milk. Of 70 cases of tuberculosis of the bones and joints in children examined by Fraser °® in Edinburgh, 41, or 60 per cent., were due to bacilli of the bovine type and in the greater number of cases the history indicated that the infection was introduced by cow’s milk. In 261 cases of bone and joint disease examined by Eastwood and Griffith,’® bacilli of the bovine type were found in 55, or 21.1 per cent. Of these latter, 29 per cent. were from patients under 10 years of age and 9.4 from patients over that age. Seventeen cases of genito-urinary dis- eases were examined. Bacilli of the bovine type were found in three cases of kidney disease in persons 25, 19 and 20 years old, respectively. Twelve and one-half per cent. of the fatal cases of tuberculosis in children under 5 years old studied by Park and Krumweide™ were 8 Cited by Rievel, Milchkunde, p. 110. ® Cited by Ostertag, Zeitschr. fiir Fleisch u. Milchhygiene, p. 69, No. 3, vol. 24; p. 118, No. 5. vol. 24. 10 Journal of Hygiene, pp. 257-309, 310-314, No. 2, vol. 15. 4 Jour. Med. Research, pp. 109-114, vol. 27. INFLUENCE OF DISEASE UPON MILK 81 due to bovine infection. They had nine cases in a found- ling asylum in children under 6 years who were nourished exclusively on cow’s milk and found bovine infection in five, or over 50 per cent. Of the fatal cases in the Babies’ Hospital in New York City 6% per cent. were due to bovine infection. These observations cannot be ignored in considering the results of Weber and Ungermann’s investigation, especially since they all indicate that bovine tuberculosis is a considerable source of infection for children and are also in accord with the results of other studies of the disease. 3. Conditions under which Milk is Infected with Tubercle Bacilli by Tuberculous Cows.—The milk of individual cows affected with tuberculosis in various forms has been tested for the presence of tubercle bacilli by injecting it into guinea pigs and by feeding it to these animals. Numerous experiments of this kind have been conducted, and upon the basis of these experiments tuberculous cows may be divided into three classes as regards the infectious- ness in their milk, viz: (a) Cows affected with tubercu- losis of the udder; (b) cows with apparently normal udders but showing clinical symptoms in other organs or parts, and (c) cows which do not show any clinical symp- toms but which have reacted to the tuberculin test. (a) Cows Affected with Tuberculosis of the Udder. —When the udder is tuberculous, tubercle bacilli are eliminated in the milk. In advanced or extensive cases of this form of the disease, the milk is very infectious; it contains from 50,000 to 100,000 and even 1,000,000 tubercle bacilli per c.c. (Ostermann), and remains viru- lent when injected into guinea pigs after it has been 6 82 PRINCIPLES AND PRACTICE OF MILK HYGIENE diluted one billion times (Ostertag).1* In the initial stages, when the tuberculous areas in the udder are small and isolated, the tubercle bacilli are less numerous, num- bering about 1000 per cc. While such milk must be diluted about 1000 times to render it non-virulent when injected into guinea pigs, it may be repeatedly fed to them undiluted without producing tuberculosis. As to the frequency of tuberculosis of the udder, in the post-mortem examination of 1200 cattle reacting to the tuberculin test, nearly all of which were dairy cows, Pearson found the udder tuberculous in 104, or 5.75 per cent. Ostertag estimates that the disease is present in the udder of 0.1 to 0.3 per cent. of all cows. In consider- ing the frequency of tuberculosis of the udder, the large number of bacilli present in the milk in advanced cases must be remembered. The milk of one cow affected with advanced or extensive tuberculosis of the udder can infect thousands of quarts of milk from other cows, if mixed with it, and may even render the entire supply of a small town infectious. (b) Cows with Apparently Normal Udders but Showing Clinical Symptoms in Other Organs or Parts.— Milk from cows in this condition frequently contains tubercle bacilli. It appears very probable that the udder is actually diseased when tubercle bacilli are eliminated in the milk of such cows. The udder may be tuberculous and yet be apparently normal. The disease is always extensive when clinical symptoms are present, and usually it is generalized—tubercle bacilli have repeatedly invaded the blood stream and have had abundant oppor- 12 Zeitschr fiir Fleisch u. Milchhy., pp. 26 and 27, No. 2, vol. xxiil. INFLUENCE OF DISEASE UPON MILK 83 tunity to locate in the udder and to produce small, fresh tubercles, too small to be discovered by palpation of the udder. Such lesions may even escape observation on post-mortem examination because of their similarity in appearance to the actively secreting udder tissue. Rick found the udder tuberculous in 17.6 per cent. of the eases of generalized tuberculosis examined by him. Joest and Kracht ** found the supramammary lymph glands tuber- culous, when tested by inoculation, in 50 per cent. of the cases examined by them of generalized tuberculosis in which the udder did not show any clinical symptoms or macroscopic lesions on post-mortem examination; some of the lymph glands were slightly enlarged but otherwise they were of normal appearance. In one-half of these cases the udder tissue was also infected. It would there- fore appear that the udder is much more frequently tuber- culous in cases of generalized tuberculosis than is gener- ally suspected. Contradictory views exist as to the possibility of tubercle bacilli passing through the sound udder. Oster- tag and Prettner injected tubercle bacilli intravenously into cows with sound udders and found the milk non- virulent when inoculated into guinea pigs. Milk may be infected secondarily with tubercle bacilli when open tuberculosis is present in the lungs, intestines, or uterus. Cows affected with open tuberculosis of the lungs swallow the greater part of the infected material coughed up, and it passes out with the feces; the tubercle bacilli are not destroyed by the digestive secretions and remain virulent. Schroeder ‘* and the British tubercu- pp. 315-316, vol. 12, No. 4, 1912. 14 Schroeder, p. 120, 25th Annual Report B. A. I. 84 PRINCIPLES AND PRACTICE OF MILK HYGIENE losis commission found the feces infectious from tuber- culous cows which did not show any clinical symptoms, but these results have not been confirmed by others. Titze, Thieringer and Jahn?® demonstrated tubercle bacilli in the faeces of cows affected with open pulmonary tuberculosis, but not in the feces of reacting cows which did not show clinical symptoms. Traum '® inoculated guinea pigs with fecal material from 36 cows, “ prac- tically all tuberculin reactors,” and none of the guinea pigs was infected with tuberculosis, although two of the cows exhibited physical symptoms of disease of the lungs. These results correspond with those obtained when samples of mixed milk from herds known to be infected with tuberculosis have been examined for tubercle bacilli. For example, O. Miiller examined samples of milk from 1598 herds in Kast Prussia and tubercle bacilli were demonstrated in the samples from only 97 herds, al- though non-clinical reactors were present in the other herds. In the 97 herds from which the samples contain- ing tubercle bacilli were obtained, cows were found which exhibited clinical symptoms of udder tuberculosis or other forms of the disease. Similar results could be cited. Reichel '’ found the faces infectious from cows which were not tuberculous but which were stabled with cows affected with open tuberculosis. It therefore ap- pears probable that the sputum coughed out by cows with open tuberculosis, or the fine spray expelled from the mouth in coughing, may contaminate the feed of other 18 Arbeit. K. Gesundheitsamt, pp. 1-34, No. 1, 1913. 16 Annual Report University of California Expt. Station, 1915, p. 40. 17 Verbal communication. INFLUENCE OF DISEASE UPON MILK 85 cows and that these cows may eliminate virulent tubercle bacilli in the faeces even when they are not infected with tuberculosis. The presence of the bacilli in the feces of tuberculous cows without open lesions in the lungs or intestines and without disease of the liver may be ex- plained on the same basis. 'Titze and Jahn found that in tuberculosis of the liver virulent tubercle bacilli may be excreted in the bile and eliminated with the feces, thus confirming the earlier findings of Joest and Kmshoff. The udder and posterior parts of the cows affected with open tuberculosis become soiled with the infected faces or vaginal discharges, and particles of this material drop off into the milk during milking, thus infecting the milk secondarily. ‘The demonstration of tubercle bacilli in the milk of individual cows does not therefore necessarily indicate that the bacilli were excreted through the udder. Milk from cows with open tuberculosis usually contains about 1000 tubercle bacilli per ¢c.c. While it does not always produce tuberculosis when fed to guinea pigs, or even when injected into them, it is often infectious and must therefore be regarded as dangerous. (c) Cows which do not Show any Clinical Symp- toms but which have Reacted to the Tuberculin Test (Non-clinical Reactors).—The experiments with indi- vidual milk from cows which had reacted to the tuberculin test, but which did not show any clinical symptoms of the disease, have given contradictory results. Ostertag, Brauer, Ascher, Miiller, Stenstrém, Bassett, and others have found the milk from non-clinical reactors to be free from tubercle bacilli, while Rabinowitch and Kempner, Schroeder, Ravenel, Mohler, Martel, Guérin, DeJong, Moussu, and Fay have found tubercle bacilli present in milk from such cows. Ostertag tested the milk of 49 86 PRINCIPLES AND PRACTICE OF MILK HYGIENE non-clinical reactors and not a single sample produced tuberculosis when injected into guinea pigs. Later,incon- junction with Brauer,’® he made a thorough test of the milk from 10 non-clinical reactors, inoculating guinea pigs, and feeding guinea pigs, calves and pigs. Not one of the experimental animals developed tuberculosis. Some of the guinea pigs in the feeding experiment re- ceived 66 grammes of milk daily for 5 months, or 33 times their body weight; 10 calves received 7 to 12 litres each day for 8 to 11 months and 20 pigs were given 1 to 6 litres daily for 4 months. O. Miller made inoculation tests on guinea pigs with the milk from 9 non-clinical reactors, and Ascher with the milk from 7, and tubercle bacilli were not demonstrated in a single case. Ostertag contends that in those cases in which tubercle bacilli were demonstrated in the milk from non-clinical reactors, the milk was infected secondarily, and in support of this view he points out that in some of the cases in which tubercle bacilli were demonstrated in the milk no lesions of tuberculosis could be found on postmortem, while in other cases lesions of open tuberculosis were present. At any rate, the evidence in its entirety indicates that the milk of non-clinical reactors is much less likely to contain tubercle than the milk of cows with tuberculous udders or which show clinical symptoms of the disease in other organs. Influence of Dilution —While these experimental re- sults indicate very accurately the conditions under which tuberculous cows contaminate milk, it must not be for- gotten that they relate to the milk of individual cows tested separately, while in practice the milk of tuber- 18 Zeitschr. fiir Fleisch u. Milchhy., p. 80, No. 4, vol. xxiv. INFLUENCE OF DISEASE UPON MILK 87 culous cows is diluted more or less with the milk of non- infected cows. The extent of the dilution will depend upon the method of handling the milk. Ordinary mar- ket milk, however, is frequently the mixed milk of sev- eral herds, but at any rate it is the mixed milk of a number of cows in the same herd. It has been demonstrated that the milk of cows affected with advanced or extensive tuberculosis of the udder may render the entire supply infectious when mixed with milk from other cows which are not tuberculous; but this is not true of milk from cows which do not show clinical symptoms of the disease. Miller and Hessler examined by inoculation samples of mixed milk from 2949 herds, each sample representing the milk from 30 to 200 cows. Tubercle bacilli were present in the samples from 156 herds. All of these herds except five were found to contain cows affected with udder tuberculosis or other forms of open tuber- culosis. In the five herds in which tuberculosis was not established clinically, Hessler is of the opinion that the tubercle bacilli were eliminated in the feces by cows with incipient cases of open lung tuberculosis which had not yet become perceptible. The other 2793 herds, in the milk samples from which tubercle bacilli were not demon- strated, certainly contained a considerable number of cows which would have reacted to the tuberculin test, judging from the extent to which tuberculosis was known to exist in the district in which they were located. Delépine examined the milk from 1385 farms and found tubercle bacilli in the samples from 294 farms. The cattle on 276 of these farms were examined and on 190 farms one or more cows were found affected with | tuberculosis of the udder, a bacteriological examination of the individual milk being necessary in some cases to 88 PRINCIPLES AND PRACTICE OF MILK HYGIENE discover the condition. After these cows were removed, the milk from these farms ceased to infect guinea pigs. No clinical cases of udder tuberculosis were found in the other 86 herds examined, but on these farms cows had been sold between the time the milk samples were col- lected and the herd was examined, or the farmer had been buying milk from other sources when the samples were collected. | Friis inoculated guinea pigs with samples of mixed milk from 28 dairy farms in and about Copenhagen and demonstrated tubercle bacilli in the samples from four farms. On one of these farms two cows with tuberculosis of the udder were found and one cow with udder tuber- culosis was found on another, while on the other two farms cows were found showing physical symptoms of tuberculosis in other organs. ‘There is no doubt that the other twenty-four farms contained cows which would have reacted to the tuberculin test. The milk from 12 non-clinical reactors was tested for tubercle bacilli by Klein and Campbell by injection into guinea pigs. ‘These cows were in a stable with 12 other non-clinical reactors which were not included in the ex- periment because they were approaching the end of the lactation period. The stable was light, well-ventilated, of suitable size and clean. ‘The cows were cleaned with a curry-comb and brush and the udders wiped with a damp cloth before each milking. All the cows in the stable were examined by inspection, palpation and auscultation when the experiment began and no symptoms indicating tuber- culosis were found. They were all in a good, thrifty condition and none had a chronic cough. (ALI suspici- ous animals had been previously removed.) 'The 12 cows used in the experiment were arranged in groups of three INFLUENCE OF DISEASE UPON MILK 89 each according to the stage of lactation and once each week the milk from each group was put into a separate can, the cows being groomed and milked in the usual manner by the regular attendants. A sample of milk was taken from each can for examination. Two guinea pigs were inoculated from each sample—one with the cream and one with the sediment. 'This was repeated each week for six weeks. Then the cows in the stable were again examined in the same way and, no symptoms indi- cating tuberculosis being found, samples of milk were collected and examined as before once a week for another period of six weeks. Altogether, 96 guinea pigs were inoculated. Thirty died of intercurrent disease and the other 66 were chloroformed two months after inoculation. A. post-mortem examination was made of every animal, but in no instance were any lesions of tuberculosis found. One of the cows in the experiment had reacted to tuber- culin over 8 years before, one 7 years, two 6 years, two 4 years, two 3 years, two 2 years, one 1 year and one 4 months before. These observations show that non-clinical reactors play a minor role in the infection of market milk with tubercle bacilli, even when the virulence of the milk is tested by the delicate inoculation test. That there is a vast difference between the number of tubercle bacilli necessary to produce infection by the mouth and by in- oculation has been demonstrated by a number of investi- gators. Ostertag and others have shown that two and a half million times more material is required to infect an animal by feeding than by inoculation. Schroeder and Cotton found that milk which would produce tubercu- losis in guinea pigs when 5 e.c. was injected into the peritoneal cavity could be fed 30 days without producing 90 PRINCIPLES AND PRACTICE OF MILK HYGIENE the disease. Findel, Reichenbach and Alexander’ found that at least 400,000,000 tubercle bacilli are necessary to produce infection when only a single dose is fed to guinea pigs and that 800,000 tubercle bacilli given fifty times by the mouth are not certain to produce infection. Ostermann *° reports that milk containing 1000 bacilli per cc. may be repeatedly ingested without effect. Fliigge and his co-workers also found that while a very few tubercle bacilli are sufficient to produce a severe tuberculosis when injected into a guinea pig, 200 are necessary when the bacilli are inhaled and 140,000,000 when they are ingested. 4, How can Contamination of Market Milk with Tubercle Bacilli be Prevented?—The information at hand shows that cows with tuberculosis of the udder are by far the greatest factors in infecting market milk with tubercle bacilli and that next in order are those with ap- parently healthy udders but showing clinical symptoms of the disease in other organs. Compared with these two classes, cows which present no evidence of tubercu- losis except a reaction to the tuberculin test are a rather insignificant source of contamination. The contamination of milk with tubercle bacilli can be most thoroughly and most certainly prevented by re- moving from the herds concerned in a milk supply the cows belonging to all three classes. This could only be accomplished by making a tuberculin test and physical examination and repeating them at certain intervals. A 19 Cited by Ostertag, Zeitschr. fiir Fleisch u. Milchhy., p. 27, No. 2, vol. xxiii. 20 Cited by Klimmer, Osterreich. Wochenschr. fiir tierheilk. 4. Tierzucht, No. 45, 1912. INFLUENCE OF DISEASE UPON MILK 91 physical examination in addition to a tuberculin test is necessary because the tuberculin test alone will not detect all cases of tuberculosis. Ostertag, for instance, tested with tuberculin nine cows affected with udder tubercu- losis and two failed to react. The adoption of such a plan, however, immediately upon the introduction of dairy inspection in districts in which tuberculosis is com- mon will meet with many practical difficulties. Few dairymen in such districts are able to bear the expense of disposing of non-clinical reactors as well as clinical eases and of replacing them with healthy cows, even with state assistance; and the state would not have suffici- ent funds to render the assistance provided by present laws if such a plan was generally adopted. Difficulty would also be experienced in replacing the reacting cattle with animals free from tuberculosis, and this would in- crease with the number of herds included in the inspection. The opposition of the dairymen concerned would be very generally incurred and there would not exist that friendly codperation between the inspector and dairy- man which is necessary to insure the most satisfactory results. .A careful and thorough physical examination repeated at intervals is next in the order of effectiveness. By this method those cows can be discovered which are the most concerned in the contamination of milk with tubercle bacilli. Such an examination should include a careful inspection and palpation of the udder and supra- mammary lymph glands; inspection of the milk in each quarter; palpation of the other superficial lymph glands; examination of the general condition of the animal; in- spection for nasal discharge; examination for cough; examination of the respiration; auscultation of the lungs; examination of the digestive tract, especially for chronic 92 PRINCIPLES AND PRACTICE OF MILK HYGIENE tympanites and diarrhoea, and inspection for vaginal discharge. In some cases it will also be necessary to take the temperature and pulse and to examine the lungs and pleura by percussion as well as auscultation, and in suspi- cious cases, when a definite decision cannot be made, it may be necessary to apply the tuberculin test to the ani- mal under examination or to collect sputum from the trachea or cesophagus, secretions from the vagina, scrap- ings from the rectum, and milk, and submit them to a microscopic examination and inoculation test (see p. 275). In tuberculin-testing such animals, a large dose of tuberculin must be used, from two and one-half to five times the ordinary dose. When the microscopic examina- tion of material from an animal of this kind gives a nega- tive result it cannot be accepted as final, but guinea pigs must be inoculated. If death does not occur earlier, the guinea pigs must be held for two months after inoculation before they can be killed for post-mortem examination. Most owners would prefer to dispose of an ordinary cow on suspicion rather than feed it for this length of time and keep it isolated and not be permitted to use the milk without heating it. It is usually more satisfactory to apply the tuberculin test in such cases. Clinical cases of tuberculosis are usually unthrifty and are generally not good milkers and the owner can usually be convinced that such animals are unprofitable. Another reason for disposing of such cows, which will appeal to the owner, is that they are sources of infection for the other cattle in the herd. As a rule, the removal of animals of this kind, advice and assistance in securing healthy cows to replace them, and proper attention to the other features of dairy inspection will gain the confidence of the owner rather than his opposition, and after a system of inspec- INFLUENCE OF DISEASE UPON MILK 93 tion of this character has been in operation for several years the tuberculin test may be added with very little objection. Fewer reactions will then be obtained and the reacting animals can be more readily replaced with non-tuberculous animals. When milk is produced especially for children’s use, however, the greater susceptibility of children to tubercle bacilli of bovine origin must be taken into account, and the most thorough methods for protecting milk from con- tamination with tubercle bacilli should be applied. Children’s milk should therefore be obtained only from herds which are tuberculin-tested at least once a year and which are subjected to a physical examination at least once each month. The efficiency of the clinical examination of dairy cows in preventing the contamination of a milk supply with tubercle bacilli as compared with the bacteriological examination of the milk for the presence of the bacilli is fairly presented in the following statement from the report of the British Commission on tuberculosis: “The presence of tubercle bacilli in cow’s milk can be dis- covered, though with some difficulty, if proper means be adopted,” but “it is much easier to demonstrate with certainty by clinical examination that a cow is affected with tuberculosis and will in consequence perhaps pro- duce tuberculous milk.” Furthermore, milk from a cow eliminating tubercle bacilli is not constantly infected. On certain days, the organisms may be absent entirely or present in only small numbers. A single examination may therefore give misleading results. The destruction of tubercle bacilli in milk by heat is considered in the chapter on pasteurization (page 203) . 94 PRINCIPLES AND PRACTICE OF MILK HYGIENE Diagnosis of Tuberculosis of the Udder.—For a time after the disease has been established in the udder, the tubercles are not large enough to be discovered by palpation and the milk retains its normal appearance, but during this initial stage of the disease symptoms are usually present in other organs which enable one to discover the presence of the disease by physical examination. In 119 cows affected with tuberculosis of the udder, Lungwitz 7! found tuberculosis in other organs in every one. The observations of Rick and of Joest and Kracht, already quoted, show that the disease is usually gener- alized when the udder becomes infected. Tuberculosis of the udder runs a slow, insidious course. The perceptible changes in the udder which indicate its presence are firm nodules, which are neither hot nor painful, or a rather diffuse painless induration without local increase of tempera- ture, in one or more quarters. Later, abscesses may form and rupture (mixed infection); atrophy may also occur. The posterior quarters are most commonly affected. The supra- mammary lymph glands may be enlarged, while the udder is of normal appearance, but in these cases the udder is usually also infected. In rare cases, the disease runs an acute course, the udder showing the symptoms of acute inflammation. In contrast with what occurs in other forms of udder disease, the milk remains of normal appearance for eight to ten weeks, although it may be highly virulent. Finally, it becomes thin and transparent like water, assumes a yellowish color and con- tains small clots or flakes. When it is permitted to stand, a pus-like sediment is deposited with a yellow, transparent fluid resembling serum above it. The acidity is reduced one-half (Raudnitz), or the reaction is even sometimes alkaline (Oster- tag). In advanced cases, the secretion of milk ceases and’ only a purulent fluid in moderate amount can be obtained from the affected quarter. Diagnosis of Open Tuberculosis—(a) Pulmonary Tubercu- losis.—The most characteristic symptom is a chronic cough, at 21 Leblanc, Diseases of Mammary Gland (Nunn’s transla- tion). INFLUENCE OF DISEASE UPON MILK 95 first vigorous, later weak. The respiration is often unchanged, but in advanced cases it is usually rapid and labored. Sometimes there is a purulent nasal discharge. Percussion does not usually give much information ; on auscultation increased vesicu- lar murmur, rales, and indefinite sounds may be detected. These symptoms are usually accompanied by anemia, unthriftiness, emaciation, dull and sunken eyes, variable or poor appetite, diarrhea, repeated bloating after meals, or distention of the ju- gular vem. In advanced cases the pulse is accelerated and soft. (b) Intestinal Tuberculosis——The symptoms of intestinal tuberculosis are not characteristic. Repeated attacks of colic and constipation alternating with diarrhcea are the most sus- picious. The intestinal discharges may be quite fluid and frequently contain mucus and pus, sometimes blood. The diges- tive disturbances which are nearly always present in advanced tuberculosis are usually due to the involvement of the intestines, but on the other hand, they may be entirely absent when the intestines are tuberculous. (c) Tuberculosis of the Uterus.—A turbid, mucous or muco- purulent discharge, yellowish or rather ichorous and of foul odor, is a constant symptom of tuberculosis of the uterus. Frag- ments of caseous material or streaks of blood are sometimes present. The cow is sterile and frequently in heat. On rectal examination the sacral lymph-glands may be found enlarged or the horns of the uterus hard and nodular. When the mucous membrane of the vagina or vulva is tuber- culous, ulcers or nodules are present, together with a similar discharge. Enlargement of the superficial lymph glands is an important symptom. | While these symptoms in themselves are not sufficient to justify a positive diagnosis of tuberculosis, nevertheless when they are presented by an animal in a herd in which tuberculosis is known to exist, and when other possible causes for them can be excluded, an error will not often be made if the animal is regarded as tuberculous. In doubtful cases the tuberculin test can be applied or a microscopic examination or an inoculation test made. 96 PRINCIPLES AND PRACTICE OF MILK HYGIENE APHTHOUS FEVER OR FOOT AND MOUTH DISEASE In the milder forms of foot and mouth disease the milk secretion may not be affected, but in the more severe cases the milk flow is reduced one-half and the milk is con- siderably changed in composition and appearance. The alterations are similar to those observed in inflammation of the udder. The albumin, globulin and salts are in- creased in quantity, while the sugar, casein, and usually the fat are decreased, although sometimes the fat is in- creased. ‘The milk becomes thin, and after it stands for a while a layer of slimy, dirty cream forms at the top of the fluid and considerable sediment is deposited at the bottom of the vessel. When examined microscopic- ally, the sediment is found to be rich in cells—epithelial cells, leucocytes, and red-blood cells. The milk coagu- lates when boiled, reacts positively to the alcohol test and contains a large amount of catalase. Nocard has shown that the milk of affected cows does not contain the virus of foot and mouth disease when it is drawn from the udder in a manner which pre- vents external contamination. But when vesicles or ulcers are present on the teats or udder it is not possible to draw milk in the ordinary way without it becoming contaminated with the virus. Merely a trace of the serum from the vesicles is sufficient to render 50 to 100 quarts of milk infectious. Practical experience indicates that the milk of affected cows is frequently infectious. Fur- thermore, the extraordinary facility with which the virus is disseminated makes it extremely probable that all of the milk of a herd in which the disease exists may be infected secondarily. The disease may be transmitted to man through milk, INFLUENCE OF DISEASE UPON MILK 97 and also to cattle and swine. It may also be transmitted by butter and cheese. Man may be mildly or severely affected; in some instances, the disease has terminated fatally. The symptoms are fever, weakness, conjuncti- vitis, nausea, vomiting, and diarrhoea, with formation of vesicles on the mucous membrane of the lips, mouth or nose, and on the ears, fingers or other places on the body; sometimes the skin is red and the joints painful. The sale of milk from herds in which foot and mouth disease exists should not be permitted, unless it is heated sufficiently to destroy the virus and is not changed in appearance. The virus is not very resistant. A tempera- ture of 50° C. (122° F.) for 15 minutes; 70° C. (168° F.) for 10 minutes; or 85° C. (185° F.) momentarily will destroy it (Ernst). COWPOX Cowpox is closely related to variola or smallpox of man. Before vaccination was introduced, when smallpox frequently became epidemic, it is very probable that cow- pox often originated from this source. Vaccinia of man is also transmissible to cattle and many instances are on record in which cows have been infected by vaccinated persons. Infection takes place during milking as a rule, the contagion being rubbed into the skin of the teat by the hands of the milker. The disease is therefore most commonly seen in cows in milk. It usually begins with a rise of temperature, but this may pass unnoticed unless it is accompanied by dullness and loss of appetite, as is sometimes the case. The teats and neighboring parts of the udder become swollen, hot, and painful. In two or three days, papules appear, which may be as large as a pea and which are surrounded by a red area. On the 7 98 PRINCIPLES AND PRACTICE OF MILK HYGIENE udder they are round; on the teats oblong, with the great- est diameter parallel with the length of the teat. In a day or two they change into vesicles of a bluish-white or yellowish-white color. The vesicles ripen into pustules in eight or ten days and a depression or umbilication appears in the top, after which they rupture and leave an ulcer, or dry and heal under a scab. They may be ruptured during milking before they are ripe. The milk may become thin, bluish, and of lighter specific gravity than normal; it may be nauseating and may coagulate very readily. The acidity may be below normal. ‘These changes, however, do not always occur. When the disease is complicated with parenchymatous mastitis, as sometimes happens, then the milk undergoes the pronounced changes which occur in the latter con- dition (see page 109). Cowpox is transmitted from cow to cow by the milker and by infected bedding, fodder, and stalls. The disease is also transmissible from the cow to man through milk. There is no proof that the virus is excreted through the udder, but as the pox are located on the teats and the adjacent parts of the udder it is practically impossible to draw the milk without the virus contained in the ves- icles and pustules getting into it. Stern saw cowpox transmitted to a large number of children by milk from a dairy in which the disease was enzootic. The children were affected with an eruption on the face which healed under a scab. Not many such observations have been recorded, however. The reason for this is that the general custom of vaccinating against smallpox has rendered most persons immune to the disease. The transmission of the disease to the milkers by direct infection of wounds on the hands or fingers has been more frequently ob- INFLUENCE OF DISEASE UPON MILK 99 served; in some cases the face has been affected in this way. Milk from cows affected with cowpox should not be used for food. When the disease is enzootic, the healthy and diseased cows should be separated and separate milkers provided for each class. This is especially im- portant when the milk is to be used by children. The virus of cowpox is destroyed by a temperature of 48° C. (119° F.). Milk from infected animals which has not undergone any physical change and milk which has been exposed to infection may be rendered safe by heating to this temperature. False Cowpox—Cowpox should not be confused with a condition more commonly affecting the udder which is known as false cowpox. In this condition, small nodu- lar swellmgs which may be as large as a pea appear on the teats and neighboring parts of the udder, rupture in a few days, and then heal under a scab. The teats are not hot, swollen or tender and there is no red area around the nodules, as in true cowpox; fever is also absent. The condition is supposed to be caused by the ordinary pyo- genic cocci, which are rubbed into the skin during milk- ing or enter through wounds. Cows with teats covered with a fine skin seem to be most susceptible. The condition may be transmitted from cow to cow by the hands of the milker, but is not transmissible to man. The milk is not affected except in so far as it may be contaminated with purulent matter from the ruptured nodules. There is only a small quantity of this material and the con- tamination from this source therefore can only be very slight. Furunculosis of the Udder is sometimes called cowpox by dairymen. This condition usually occurs sporadically, 100 PRINCIPLES AND PRACTICE OF MILK HYGIENE but it is occasionally enzootic, especially when musty or mouldy straw is used for bedding. It is most fre- quently seen in fresh cows, after they have been put on full feed, and it is probably for this reason that the fu- runcles are spoken of as feed boils. Firm, painful, nodu- lar swellings, varying in size from a pea to a walnut, appear in the subcutaneous tissue of the udder. In seven or eight days a dark area of puriform softening develops in the centre of each individual swelling, which subsequently ruptures at this point and discharges its contents of pus mixed with shreds of tissue. This dark patch, or the scab of dried blood which subsequently forms at the point of rupture, has given the process the popular name of black scab in some sections. The milk secretion is not affected, but the milk may be contami- nated secondarily with the purulent discharge. ANTHRAX The question of using the milk from a cow affected with anthrax does not often arise in practice because, as arule, the milk secretion ceases suddenly with the onset of the fever, while in those cases in which it continues it is reduced to a small quantity and is very much changed in appearance. It is more yellowish than normal, slimy, sometimes bloody, with a bitter taste, and after standing undisturbed for a few hours separates into a layer of cream and of serum. Anthrax bacilli are excreted through the udder only in the advanced stages of the disease, after they have invaded the blood stream and when the udder is affected. But the chances of milk becoming infected secondarily are very great. The bloody discharges and the manure from infected animals contain the anthrax INFLUENCE OF DISEASE UPON MILK 101 bacilli and their spores, and the spores may also be present in the dust of the stable and in the dust of straw and hay from infected fields. The organisms may gain access not only to the milk of the affected cow, but also to the milk of other cows in the stable. Anthrax bacilli and spores entering milk in this way may multiply rapidly, as milk is an excellent culture medium for this organism. While the bacilli are digested by the gastric juice, the spores are not affected and in disturbances of digestion the bacilli may also escape destruction. Ernst mentions a typhoid fever patient who developed intestinal anthrax after drinking milk from a cow with a malignant pustule on the udder. All milk from a herd in which anthrax is present must therefore be regarded as dangerous to man until proper precautions are taken to prevent the secondary infection of the milk from the cows which are not diseased. Diseased and dead animals should be at once removed from the stable, which should be thoroughly cleaned and disinfected. McFadyean recommends that the tempera- ture of every exposed cow be taken each day before milk- ing for seven to ten days, and that all those showing a rise of temperature be treated as suspicious cases and taken out of the stable, the milk not being used. RABIES Cattle are usually infected with rabies by being bitten by a rabid dog. Frequently several animals in a herd are infected at the same time. While the virus of rabies is to be found in its purest and most concentrated form in the central nervous system, it is also present in the milk of affected animals as well as in the secretions 102 PRINCIPLES AND PRACTICE OF MILK HYGIENE of the salivary and lachrymal glands and pancreas. Numerous feeding experiments with milk and other sub- stances from rabid animals show that the virus is not absorbed, and that the disease is not produced, when the mucous membrane of the digestive tract is intact and the digestive functions are acting normally. In the upper part of the digestive tract, stratified squamous epithelium acts as a barrier to the entrance of the virus into the blood stream and when it reaches the stomach it is digested by the gastric juice. But when wounds are present in the mucous membrane of the lips, mouth or throat, or when the secretion of gastric juice is disturbed, the ingestion of milk containing the virus of rabies may produce the disease. Milk from cows affected with rabies must there- fore be regarded as dangerous. Whether the milk of infected cows contains the virus before symptoms of the disease appear, as is the case with the saliva of dogs, is not known. Until this question is determined it will be advisable not to use the milk of a cow which has been bitten by a rabid dog until it is determined that infection did not occur. ACTINOMYCOSIS Actinomycosis usually affects the maxillz, tongue or other parts about the head, but it sometimes occurs in the udder, also in the lungs and other internal organs. When present in the udder it is usually of primary origin, 7.¢e., the infection enters through the teat canal. Actinomycosis of the udder is generally indicated by the presence of one or several firm nodules of the size of a bean up to a hen’s egg in one or more quarters of the organ. These nodules consist of a thick wall of connec- tive tissue surrounding a purulent centre in which the actinomyces may be seen in the form of sulphur-yellow INFLUENCE OF DISEASE UPON MILK 103 granules. They may rupture internally or externally and discharge pus containing the fungi. The milk cis- tern may be filled with the nodules. Sometimes the dis- ease appears in the udder in a miliary form; the affected quarters are enlarged, hard and somewhat nodular, and on section numerous very small nodules of granulation tissue with softened purulent centres are found dissemi- nated through the gland tissue. Similar nodules may be found on the mucous membrane of the larger canals and cistern. Numerous actinomyces are found in the soft- ened centre of the nodules. As a rule, actinomycosis of the udder has not been recognized until after the slaughter of the affected animal, consequently nothing definite is known regarding the appearance of the milk in this condition. Up to this time, actinomyces have not been demonstrated in milk, but they are no doubt ex- creted with the milk when the actinomycotic nodules rup- ture into an alveolus or duct of the udder. The milk may be infected secondarily when an actinomycotic nodule in the udder ruptures externally or when an actin- omycotic tumor in the maxilla or adjacent parts opens. In such cases the discharge contains not only actinomyces but also bacteria, particularly the pyogenic organisms, and these, too, may gain access to the milk. There is no record of the transmission of actinomy- cosis to man through milk. 'This may be due in part to the slow development of the disease, as in the case of tuberculosis. Infection with actmomyces may occur in man, as it does in cattle, through the food, especially when wounds exist in the mouth or other anterior parts of the digestive tract. Since there is a possibility of the transmission of this disease by milk, it is advisable to exclude from dairies all cows with actinomycosis of the 104 PRINCIPLES AND PRACTICE OF MILK HYGIENE udder or with open, discharging actinomycotic tumors. Milk from cows in the latter condition is further objec- tionable because it may contain pus and pyogenic or- ganisms, and, in advanced cases, for the additional reason that the general condition is affected, the animal becom- ing emaciated, weak and dull. MILK SICKNESS OR TREMBLES Cattle and horses when pastured on certain lands in circumscribed areas in the United States develop a dis- ease known as milk sickness or trembles. Its etiology has been the subject of much speculation and investiga- tion. In 1907 Jordan and Harris isolated in pure culture from the blood and organs of animals dead of the disease a spore-forming bacillus with which they succeeded in reproducing the disease in experimental animals. They have given this organism the name of Bacillus lactimorbi. The principal symptoms of the disease are violent trem- bling and great restlessness, followed by paralysis. The animal may fall and die suddenly, but usually it lies sev- eral days in a paralyzed condition. The disease is trans- mitted to man through the milk, butter, and meat from affected animals. The symptoms in man are severe vomiting, difficult breathing, subnormal temperature, paralysis, and death. II. Diseases or CATTLE WHICH MAY RENDER MILK HARMFUL TO MAN. INFLAMMATION OF THE UDDER—MASTITIS Cows are very frequently affected with mastitis, a disease of great economic as well as hygienic importance. There are three forms of the disease: (1) Catarrhal mas- titis, which may be either mucous or purulent, and which INFLUENCE OF DISEASE UPON MILK 105 runs a subacute or chronic course; (2) parenchymatous mastitis, which is purulent and acute, and which is some- times accompanied by abscess formation and gangrene, and (8) interstitial mastitis, which may be a simple in- flammation or a phlegmonous condition. The three forms differ in the type of the inflammation (acute or chronic), the part of the udder tissue affected, the effect upon the milk secretion, and in the character of the bacteria con- cerned. One form may be associated with another. The disease is commonly called “ garget”” by dairymen and farmers. 1. Catarrhal Mastitis—From a hygienic standpoint, catarrhal mastitis is of greatest importance because it occurs more frequently than the other forms and also because the milk may contain the causative bacteria be- fore clinical symptoms or marked changes in the milk are apparent and for a time after they have disappeared. This latter circumstance has been the inspiration of numerous efforts to discover a method of examining milk by which this disease could be detected in its incipiency. Catarrhal mastitis is a mucous or purulent catarrh of the mucous membrane of the teat canal, milk cistern, and large milk ducts. It is frequently accompanied or followed by a productive inflammation of the submucous and interstitial connective tissue, in which case it often terminates in atrophy of the gland tissue and loss of function. It is usually caused by streptococci of varying degrees of virulence; sometimes, but not often, mucous catarrh occurs without the intervention of bacteria from the effects of cold or overfeeding. The symptoms are never pronounced. The history of the cow is of great assistance in detecting incipient cases, although it is sometimes difficult to obtain. A statement that the cow 106 PRINCIPLES AND PRACTICE OF MILK HYGIENE “milks hard,” i.e., that there is difficulty in expressing the milk through the teat canal, or that the milk is not “Jet down ” or is “ drawn up,” or that the cow has recently developed a tendency to kick during milking, should ex- cite suspicion of the presence of the disease. ‘The first condition is due to obstruction of the teat canal by swell- ing of the mucous membrane or by dried secretion; the others occur because milking is painful. Among the first noticeable symptoms of the disease are changes in the milk stream expressed from the teat. This may be split, deflected from the proper direction, or it may not be cut off promptly and may therefore smear the end of the teat—all indications of catarrh of the mucous mem- brane of the teat canal. In such cases small yellow crusts may be found covering the opening of the teat canal, but crusts of dried milk may also be present at this point when the sphincter of the teat canal does not close properly. When pressure is exerted upon the lower end of the teat, a drop of pus or mucus may be squeezed out of the teat canal or the thickened mucous membrane may project through the opening. Later, the mucous membrane of the cistern may become thickened, in which case a cord about as thick as a lead pencil is felt running through the middle of the teat when the teat is rolled between the thumb and fingers. Flat, disc-shaped thickenings about the size of a quarter dollar and nodular indurations may be present in the upper limits of the cistern when the mucous membrane of the lower end of the large milk ducts is thickened. Growths upon the wall of the cistern or teat canal (“ spider in the teat”) may also be dis- covered by palpation. The induration usually extends slowly into the interstitial tissue, generally from the teat INFLUENCE OF DISEASE UPON MILK 107 upward, producing a hard firm area (“ cake,” “ caked udder,” “cold garget”’), which may eventually involve the entire quarter. The newly formed connective tissue subsequently contracts and causes atrophy of ute gland tissue and loss of function. In the early stages of the disease, and also throughout mild cases of mucous catarrh, the milk does not show any marked change at the time it is drawn from the udder. Very often it contains small flakes, some of which may be as small as a pin-head; they may be present only in the first milk drawn, but sometimes they do not appear until the middle or at the end of the milking. After the milk stands for a time, or is centrifugalized, a grayish- yellow sediment is deposited and a dirty-gray, clumpy or granular cream layer is formed. In severe cases of mucous catarrh, the secretion becomes slimy and viscid. In purulent catarrh, the secretion of milk decreases while the pus cells and fibrin increase and the fluid ob- tained from the affected quarter gradually changes to a thick, yellowish, purulent exudate or to a yellowish serum containing clumps of pus and fibrin. Frequently, the exudation ceases entirely and the milk secretion does not return until the next lactation or not at all. The chemical composition of the milk is only slightly changed at the beginning of the disease, the lactose being de- creased and the mineral salts, especially the sodium chlo- ride, increased, while the other constituents are present in the usual amount. Later, there is a greater decrease in the lactose, the casein is also below normal, and the fat is usually decreased, while the albumin, globulin, and mineral salts are increased. Fibrin is also present. ‘The reaction of the milk is usually, but not always, alkaline. The taste is salty or bitter. Cells are present in large 108 PRINCIPLES AND PRACTICE OF MILK HYGIENE numbers in the sediment and cream, especially the poly- morphonuclear leucocytes in purulent catarrh. The catalase content is increased. Coagulation occurs when the alcohol or the boiling test (see pages 284, 285) is applied. On account of the difficulty of detecting catarrhal mastitis in its early stages, the determination of the leuco- cytic content of samples of market milk has sometimes been relied on to discover the presence of the disease. It has been demonstrated that cases of catarrhal mastitis may be detected by this method but we have no means of knowing how many of such cases escape discovery; there is reason to believe that many are overlooked. The ex- amination of samples of milk from individual cows by means of the catalase test is the most efficient method of detecting the disease (see page 287). When numerous very small, punctiform, brownish colonies appear in the plates prepared for determining the number of bacteria in milk and these are found upon microscopic examination to consist of streptococci in long chains, an examination of the herd will usually discover the presence of one or more cases of catarrhal mastitis. A special form of purulent catarrhal mastitis which leads to multiple abscess formation is caused by the Bacil- lus pyogenes. The secretion has afoul odor. The disease occurs most commonly in “ dry ” cows, but is usually not discovered until they become “ fresh.” 2. Parenchymatous Mastitis——The detection of this form of mastitis offers no difficulties to the dairy inspec- tor. It is attended with an immediate and pronounced swelling of the affected portion of the udder and the milk at once presents marked changes. As the name indicates, it is an inflammation of the alveoli and small tubules of INFLUENCE OF DISEASE UPON MILK 109 the udder and is usually caused by the Bacillus phleg- masia iiberis or other varieties of colon bacilli, sometimes by organisms of the paracolon or paratyphus group, the enteriditis bacillus or by staphylococci. Septicamia may develop in the course of the disease. Severe cases may terminate in gangrenous mastitis. In the beginning of the disease, and throughout mild cases, a turbid fluid resembling whey in appearance and containing flakes of casein, is obtained from the affected quarter. Later, in cases of medium degree, the fluid resembles serum and contains clots of fibrin. In the more severe cases, the secretion is discolored with blood. In gangrenous mas- titis, a small amount of bloody-serous, dark, foul-smelling fluid, which contains gas bubbles, may be obtained from the affected quarter. The chemical changes which occur in the milk in parenchymatous mastitis are similar to those which take place in catarrhal mastitis. There is a de- crease in the lactose, which is sometimes entirely absent; the fat is usually decreased, although sometimes it is in- creased; the casein is decreased, while the albumin, glob- ulin, and salts, especially sodium chloride, are increased. The taste is salty or bitter. There is an increase in the content of catalase and coagulation takes place when the alcohol or boiling test is applied. 3. Interstitial Mastitis——The simple, traumatic form of interstitial mastitis, in which the inflammatory process is limited in extent and rather mild, has no important effect upon the milk secretion, but when the disease is due to the entrance of bacteria through fissures or wounds, as is most frequently the case, a phlezgmonous inflammation occurs in the subcutaneous or interstitial connective tissue which is accompanied by a rise of the body temperature, sometimes to 107° F., and other symp- 110 PRINCIPLES AND PRACTICE OF MILK HYGIENE toms of constitutional disturbance. There is then more or less extensive and painful swelling of the affected quarter which begins at the teats and extends upward. The milk secretion is somewhat reduced in quantity in the beginning of the disease, but is otherwise unchanged. Later, the secretion from the affected quarter is dimin- ished ; the fat is decreased and the milk has a pale, watery appearance. The inflammation may extend into the gland tissue, in which case the milk will undergo the same changes as in parenchymatous mastitis. Harmful Properties of Mastitis Milk.—In mastitis the secretion from the udder nearly always contains bac- teria which may be harmful to man. In the catarrhal form streptococci are usually present, sometimes staphy- lococci or the Bacillus pyogenes. In the parenchymatous form bacteria of the colon group are usually present, sometimes bacilli of the paratyphus or paracolon group, the enteriditis bacillus, or staphylococci. In catarrhal mastitis the bacteria may be present when the milk is of normal appearance and before clinical symptoms appear and also after the clinical symptoms have subsided and the milk has again become normal in appearance. Bac- teria not only occur in the secretion from the affected quarter but they may also be present in the milk from the other quarters. The skin of the teats and udder is con- taminated by the secretion from the diseased quarter and some of this infected material can easily fall into the milk pail during the drawing of milk from the other quarters. Secondary infection of the milk is also likely to occur when the secretion from the diseased quarter is milked onto the floor, as is frequently done. The mastitis bac- teria find an excellent culture media in milk and rapidly multiply when the milk is kept at room temperature. INFLUENCE OF DISEASE UPON MILK lil Considering the frequency of the catarrhal and paren- chymatous forms of mastitis in dairy cows, cases of illness in man resulting from the ingestion of milk from cows affected with this disease have not been reported as often as would be expected. There are several reasons for this. The milk from a diseased cow may be diluted with milk from cows in normal condition to such an extent as to render the mixed milk harmless. Furthermore, some of the mastitis bacteria have a relatively low virulence for man. Finally, it rarely happens that the physician is able to establish the connection between the disease in his patient and the cow affected with mastitis, even when milk from the latter is the cause of the disease. Nevertheless, there are on record numerous cases of ill- ness in man caused by the ingestion of milk from cows affected with mastitis, the symptoms in these cases being nausea, vomiting, and diarrhoea, sometimes associated with fever, faintness, languor, and cramps in the legs. In two instances the milk which was the cause of the disease had been boiled. It is not known whether the illness in these cases was due to a heat-resisting toxin or to bacteria which survived the heat because of the protection fur- nished by the membrane which forms on the surface of milk when it is heated. Numerous epidemics of septic sore throat have been reported in which the infection was transmitted by milk. In some of these epidemics, cows affected with strepto- coccic mastitis were found to be the source of the infec- tion, but in the other outbreaks the circumstances seemed to point to the infection of the milk by dairy workers suf- fering from the disease. To account for the persistence of streptococci for several days in the milk supplies involved in the second group of epidemics, the theory has been 112 PRINCIPLES AND PRACTICE OF MILK HYGIENE advanced by Theobald Smith that the offending organ- isms were introduced into the udder of some of the cows by infected milkers, multiplied there without producing any changes in the organ or in the milk, and were elimi- nated in the milk in large numbers at each milking. In two of the epidemics in the United States (Chicago 1911, Baltimore 1912), the milk which spread the disease had been subjected to a pasteurizing process. Rosenau observed that when the Streptococcus pyogenes is grown in raw milk it is modified to correspond with the strepto- coccus of epidemic sore throat. Milk from cows affected with catarrhal and paren- chymatous mastitis is also objectionable because the pus which it contains often gives it an unpleasant taste and frequently causes it to putrefy and to curdle quickly. The pus itself may be harmful to children, even if no bacteria are present. The greatest harm, however, is done by the bacteria. In the phlegmonous form of inter- stitial mastitis the presence of fever and other constitu- tional disturbances renders the milk unsuitable for food; there is also the possibility that the parenchyma of the udder may at any time become affected and the causative bacteria would then be eliminated in the milk. Therefore, when a cow is affected with mastitis, the milk should not be used for food and, if possible, the cow should be removed from the milk stable until the udder returns to the normal condition. Cows affected with infectious streptococcic, septic, or gangrenous mastitis should always be isolated. When infectious streptococcic mastitis is present in a herd it may be necessary to pro- hibit the use of any of the milk for food unless it is boiled or pasteurized, but even then such milk should not be used for children. INFLUENCE OF DISEASE UPON MILK 113 BLOOD IN MILK A mixture of blood with the milk may occur as a result of traumatisms of the udder, such as kicking, hook- ing or treading, which cause hemorrhages or blood infil- trations into the udder tissue. The pulling or dragging to which a greatly distended udder is subjected when the cow walks may cause a tearing of the udder tissue which will permit the mixing of blood with the milk. When large blood vessels have been injured the milk is colored diffusely red. But when small vessels are torn or rup- tured, which is more often the case, only small streaks of blood are observed which disappear when the milk is shaken and do not discolor it. When such milk is centri- fugalized, the sediment shows a red color which, on micro- scopic examination, is found to be due to the presence of red-blood cells. Blood is observed in the colostrum or milk during the first week following parturition in those cases in which the udder is intensely hyperemic, resulting in a diapedesis of red-blood cells. C(DEMA OF THE UDDER Sometimes, especially in heifers with the first calf, the udder becomes very much swollen and cedematous shortly before parturition. The swelling is not hot, nor is it painful unless the skin is intensely stretched; it disappears a few days after parturition. Usually, no essential changes are observed in the milk. It is probable that some of the serous transudate is mixed with the milk, but nothing definite is known on this point. Some- times the milk contains blood. Generally, the oedema has disappeared by the time the colostral stage is passed. 8 114 PRINCIPLES AND PRACTICE OF MILK HYGIENE INDIGESTION When the digestive functions of the dairy cow are disturbed, as in gastro-intestinal catarrh, there is not only a decrease in the quantity of milk secreted, but quite frequently the milk has a bitter or salty taste and coagu- lates prematurely (six to eight hours after milking). It contains less fat than normal milk and sometimes appears thinner and of a yellow color. Milk from cows in this condition may possess irritant properties and when in- gested unmixed with the milk of other cows may produce diarrhoea, especially in children. The milk may undergo similar changes in other in- ternal diseases which do not directly involve the udder. Spoiled Feed.—The milk of cows fed on mouldy, fermented, or putrefied feed has produced diarrhoea in persons ingesting it. This effect has been attributed to the elimination in the milk of abnormal substances con- tained in such feeds, but it is possible that the organisms causing the changes in the feed may have gained access to the milk during milking and caused changes in the milk itself which brought on the diarrhcea. SEPTIC OR HEMORRHAGIC ENTERITIS This disease consists of a severe or bloody diarrhoea associated with a high temperature and other constitu- tional disturbances. It may occur sporadically or en- zootically, especially among young cattle. According to Jensen, it is caused by bacteria of the paracolon group which circulate in the blood and which are also present in large numbers in the fecal discharges. Secondary in- fection of the milk during milking is almost certain to occur since the udder, thighs, and flanks of the diseased animal will be soiled by the fecal matter. The bacteria, INFLUENCE OF DISEASE UPON MILK 115 having entered the blood stream, may also be excreted in the milk when hemorrhages have occurred in the udder tissue. ‘Two instances are reported in which milk from cows affected with this disease has produced disease in man. One individual was affected with diarrhoea, weak- ness, and headache, while the other exhibited symptoms resembling typhoid fever. Cows affected with a severe or bloody diarrhoea or with a diarrhoea associated with fever should be removed from the milk stable, since they are likely to infect not only their own milk but also the milk of other cows with pathogenic bacteria. The stable should be cleaned and disinfected. SEPTIC METRITIS In acute septic metritis, the milk secretion usually ceases with the sudden onset of the fever and the animal generally dies in a few days, so that the question of using the milk does not often have to be considered. In the less acute cases, a large amount of chocolate-colored fluid, which is frequently putrid, is excreted from the uterus and soils the tail, inner surface of the thighs, and udder, as well as the bedding, stall, and suroundings. This fluid may contain staphylococci, streptococci, bacilli of the colon and paratyphus groups, and putrefactive bacteria. These organisms may enter the milk during milking. The milk of such animals usually gives a positive reac- tion to the alcohol test, indicating that some of the prod- ucts of the disease are absorbed from the uterus and eliminated through the udder. The foul odor of the uterine discharges and the odor of antiseptics which may be used in the treatment of such cows will be absorbed by the milk. While no cases of disease in man from the use of milk from cows affected with septic metritis have 116 PRINCIPLES AND PRACTICE OF MILK HYGIENE been reported, there is no doubt that the milk is injurious to health because numerous cases of meat poisoning are on record from the use of meat from cows slaughtered while suffering from this condition. Cows affected with septic metritis should therefore be removed from the milk stable and the milk should not be used for food. RETAINED PLACENTA Following retention of the placenta, there is a dis- charge from the uterus which frequently contains par- ticles of the fetal membranes and cotyledons which are undergoing putrefaction, also pus, pyogenic organisms, and putrefactive bacteria. The tail, thighs, and udder become soiled with the discharges and the milk may be contaminated during milking. In cases where the milk has been centrifugalized and the sediment examined micro- scopically, large numbers of staphylococci and diplococci have been found. The milk will also give a positive re- action to the alcohol test, indicating that the secretion is not normal. Milk from cows with a purulent or putrid vaginal discharge should not be used for food purposes. Such cows should not be placed in the milk stable until the condition disappears, as there is a possibility of the discharge contaminating the milk of the other cows. INFECTIOUS ABORTION The milk of cows which have aborted contains the Bacillus abortus Bang very frequently, in some cases for months after the abortion. Immediately before and for several weeks after abortion, the bacillus is also elimi- nated through the vagina and may infect the milk second- arily. When the placenta is retained, the vaginal dis- charge also contains pyogenic and putrefactive organ- INFLUENCE OF DISEASE UPON MILK 117 isms. At the time of abortion the udder secretion fre- quently assumes the characteristics of colostrum. When injected into guinea pigs or fed to them, milk containing the abortion bacillus produces proliferative changes similar to those caused by the tubercle bacillus. The organism is also pathogenic for animals of several other species. This widespread pathogenicity and its frequent occurrence in milk suggested the desirability of investigations to determine if the organism was con- cerned in the sclerotic changes occurring in the organs and tissues of man and the domestic animals. Mohler and Traum inoculated guinea pigs with material from twenty-eight tonsils and adenoids from milk-consuming children. The material from two of the tonsils produced lesions in three guinea pigs, but the Bacillus abortus was recovered only from the lesions in one of these animals. Whether the organism was actually responsible for the change in the tonsil or whether it merely happened to be lodged on the surface could not be determined. Schroeder also made a number of similar tests, all with negative results. Mohler tested the blood serum of twenty-five persons with the complement fixation and agglutination tests and obtained negative results in all cases, while Larsen and Sedgwick, in applying the com- plement fixation test to the blood serum from 425 chil- dren, obtained 73 positive reactions (17 per cent.). Ramsey tested the blood of 116 children in the same manner, but the reaction was positive in only seven cases. Nicholl and Pratt obtained positive reactions with the agglutination test on the blood serum of several children. No definite statement can be made as to whether the anti- 118 PRINCIPLES AND PRACTICE OF MILK HYGIENE bodies responsible for these positive reactions were present because the individuals from which the blood samples were obtained had actually passed through some form of disease due to the abortion bacillus or whether they were the results of a passive immunity due to the ingestion of milk containing the bacillus or its antibodies. But it has been demonstrated in a number of experiments that after the ingestion of an organism in large num- bers the specific antiLodies may be present in the blood without the organism producing disease, and there is some reason to believe that antibodies contained in the milk may be absorbed by the blood from the intestinal canal of children (see page 43). However, there is no definite information that abortion bacilli in milk have any injurious effect upon the health of individuals in- gesting such milk. OTHER DISEASES Any disease of the dairy cow attended with a con- siderable disturbance of the general condition usually causes a decrease or a complete cessation of the milk secretion. Although the milk is generally of normal appearance when secretion continues in such cases, it frequently contains an increased amount of mineral salts, has a salty taste and coagulates prematurely. While it is not known that milk of this kind is harmful to man, the change in its composition is sufficient to justify its condemnation as a food. When suppurating wounds or ulcerative or phleg- monous inflammations are present in any part of the body, there is danger of the milk being infected with the pyogenic organisms. INFLUENCE OF DISEASE UPON MILK 119 EXCRETION OF MEDICINES THROUGH THE UDDER A number of medicines used in the treatment of dis- eased conditions in cattle are eliminated in part through the udder, namely: iodine, mercury, lead, copper, anti- mony, arsenic, salicylic acid, antipyrin, boric acid, aloes, rhubarb, senna, croton oil, eaphorbium, morphine, strych- nine, atropine and veratrin. Although, under ordinary conditions, these substances are eliminated in the milk in small quantity, there is a possibility that milk from cows being treated with these drugs may be injurious to children and weak adults. When elimination through the normal channels is retarded by disease, they may be eliminated through the udder in larger quantity, and sub- stances which are not usually excreted through the udder may also pass out with the milk. For this reason milk should not be used for food from a cow which is being treated with medicines that are poisonous. Aloes, rhu- barb and senna affect the taste and color of milk. III. Diseases or Man TransmissisLe TuHrovucu MILK Milk may act as a carrier of the bacteria or virus of certain specific diseases of man. From time to time, epidemics in which the infectious agent has been dissemi- nated by milk have been reported, particularly outbreaks of typhoid fever, septic sore throat, diphtheria, and scarlet fever. These milk-borne epidemics have certain char- acteristics by which they may be recognized, viz: 1. The epidemic is explosive in character, a large number of cases occurring at about the same time, followed later by a rapid decrease in the number of new cases. 2. The dis- ease is limited to those families receiving their milk supply from a certain distributer; occurs in families using the greatest amount of milk and affects those individuals 120 PRINCIPLES AND PRACTICE OF MILK HYGIENE using the most milk, generally women and children. 3. The period of incubation is relatively short. 4. The dis- ease is of mild type. 5. The mortality is lower than usual. As a rule, the conclusion that the disease is dissemi- nated by milk must be based upon these characteristics and upon information obtained regarding the manner in which the milk may have been infected, rather than upon the demonstration of the infectious agent in the milk. The cause of scarlet fever is not known and consequently its presence cannot be detected by any known method of examining milk. The bacillus of typhoid fever has been demonstrated in milk several times, thus affording posi- tive proof that this organism is transmitted by milk, but the examination has been unsuccessful in a much larger number of cases. The diphtheria bacillus has been re- covered from milk in even fewer instances. ‘There are several reasons why efforts to isolate these organisms from milk which is the cause of an epidemic may be unsuc- cessful. 1. Only a small quantity of the milk, a drop or two, is subjected to examination, and this may be free from the organisms even when the latter are relatively numerous in the whole volume of milk concerned. 2. The period during which the milk is infected may be termi- nated before it is suspected and examined. 3. The or- ganisms may be overgrown by the other kinds of bacteria which are present in milk in greater number. In prac- tice, the presence of these infectious agents in milk is not suspected until several cases of disease have appeared. Even if they could be detected in milk with more cer- tainty, it would be a mistake to defer action after an epidemic has started until the milk can be examined, because this would allow more time for the dissemination of the infection. INFLUENCE OF DISEASE UPON MILK 121 TYPHOID FEVER Typhoid fever is more frequently spread by milk than any of the other infectious diseases of man except tuber- culosis. Asa carrier of typhoid infection, milk is second only to water, although the cases caused by infected water greatly outnumber those resulting from infected milk. Milk may be infected with the Bacillus typhosus in sev- eral ways. The organisms may be introduced into milk when infected water is used to wash the milk vessels and utensils. Infected water may contaminate the milk when there is a leak in the milk cooler or when a can of milk is submerged in such water to cool. Water in open or thin-walled springs, surface wells, and in streams receiv- ing surface drainage may be readily infected by excre- tions from typhoid fever patients, convalescents, and chronic bacilli carriers. Milk bottles from houses where the disease exists may be a source of infection; one or two infected bottles may contaminate the water in which they are washed or rinsed, and this water will infect other bottles washed in it. A few bacilli introduced into a vessel or bottle by infected water will multiply rapidly when milk is placed in it, for the Bacillus typhosus grows abundantly in milk. Milk may be infected directly when the cows are milked or the milk or milk vessels are handled by persons affected with the disease, by convalescents, by chronic bacilli carriers, and by those attending typhoid fever patients. The greatest danger of direct infection is from those cases in which the disease is of such a mild type that it is not recognized, the so-called walking typhoid, and from chronic bacilli carriers, 7.e., individuals who continue to excrete typhoid bacilli in the faeces and urine after they have recovered from the disease. It is estimated that 2 to 4 per cent. of typhoid fever patients 122 PRINCIPLES AND PRACTICE OF MILK HYGIENE become chronic bacilli carriers. The bacilli may also be carried by flies and be blown about in dust. The typhoid bacillus multiplies rapidly in milk and the number may be greatly increased in a short time. The milk is not changed in appearance. The organism grows in slightly sour milk; it is checked or destroyed by a high degree of acidity, but it survives the degree of acidity existing in cream ripe for churning. It may live in milk several days and may be present in fresh butter and new cheese. Bruck found virulent bacilli in butter after twenty-seven days. Typhoid bacilli in milk are destroyed when exposed to a temperature of 60° C. (140° FEF.) for two minutes (Rosenau). When an outbreak of typhoid fever occurs which has the characteristics of a milk-borne epidemic, the sus- pected milk supply should be stopped, or pasteurized under supervision, and an investigation made with the object of discovering and abolishing the source of the infection of the milk. Immediate medical attention to cases of illness affecting the dairyman, his employees, or members of their households, proper supervision of cases of typhoid fever by health authorities, the sterilization of milk bottles before refilling, and a pure water supply will greatly reduce the liability of the occurrence of such epi- demics. There is no method known which is entirely satisfactory in preventing the direct infection of milk by walking typhoid cases or by chronic bacilli carriers. Recently, some local health authorities have required that blood samples be taken from dairy employees and sub- mitted to the Widal test as a safeguard against chronic bacilli carriers; a few high-class dairies have been follow- ing this plan for some time. Several states have laws requiring dairymen to report to the local health author- INFLUENCE OF DISEASE UPON MILK 123 ities all cases of typhoid fever and other infectious dis- eases occurring in their own families and among their employees or in the families of the latter. PARATYPHOID FEVER Paratyphoid fever is also transmitted by milk, but less frequently than typhoid fever. The milk may be infected directly with the paratyphus bacilli by contact with persons affected with the disease or indirectly by polluted water being used to wash the milk vessels, uten- sils, and bottles. Water may be contaminated by fecal matter from infected persons. DIPHTHERIA A number of milk-borne epidemics of diphtheria are on record, although this disease has been less frequently disseminated by milk than typhoid fever. The diph- theria bacilli are present in the oral cavity and on the nasal mucous membrane of persons affected with the disease and may persist in these locations for months after the patient has apparently recovered. Persons who have attended diphtheria patients may also carry the bacilli. Infected persons may infect the milk directly or indirectly. In the beginning of some cases of diph- theria, the throat is apparently normal or only slightly affected. These cases and cases of chronic nasal diph- theria are most difficult to diagnose from clinical symp- toms. Because of the occurrence of cases of this type and the continuance of the bacilli in some individuals after the subsidence of clinical symptoms, it is not possible to guard entirely against the occasional infection of milk by the diphtheria bacillus. But the danger will be greatly reduced if prompt attention is given to all cases of sore 124 PRINCIPLES AND PRACTICE OF MILK HYGIENE throat occurring among dairy workers or in their fam- ilies; if persons who have attended diphtheria patients or individuals recovering from the disease are not per- mitted to handle milk or milk vessels until cultures from the throat prove to be free from the bacilli, and if re- turned bottles are sterilized before refilling. Frequently the bacilli are not very virulent. The diphtheria bacillus has been demonstrated in milk only a few times, principally because the organism is present in infected milk in small numbers and usually for only a short period. There is no doubt, however, of its transmission by milk. The milk is not changed in appearance by the growth of the organism. ‘The bacillus is not affected by the degree of acidity present in cream ripe for churning, and it may therefore be present in butter and also in other dairy products, although we have no reports of the latter carrying infection. A compara- tively low degree of heat is sufficient to destroy the organism. Itis usually killed by a temperature of 55° C. (181° F.), but occasionally some individuals survive until the temperature reaches 60° C. (140° F.). When an outbreak of diphtheria occurs with the characteristics of a milk-borne epidemic, the same pro- cedure should be followed as described under typhoid fever. SEPTIC SORE THROAT Epidemics of septic sore throat originating from in- fected milk have been reported from England for a number of years and, in recent years, several outbreaks of the disease, affecting thousands of persons, have oc- curred in this country. In some instances the infection of the milk was traced to cows affected with streptococcic INFLUENCE OF DISEASE UPON MILK 125 mastitis, but in other cases there seemed to be reason to suspect that the milk had been infected by persons af- fected with septic sore throat (see page 111). SCARLET FEVER Scarlet fever has been disseminated by milk more rarely than some of the other infectious diseases of man. The epidemics reported occurred principally in the United States and England. The infectious agent of this disease has not been discovered and it is not definitely known how it gains access to milk, but it is presumed that the milk is infected directly or indirectly by persons affected with the disease. The same action should be taken against a milk-borne epidemic of this disease as is indicated under typhoid fever. TUBERCULOSIS Tubercle bacilli of the human type have been demon- strated in milk (Hess, Rabinowitsch), and there would seem to be abundant opportunity for milk to be infected by a consumptive working in a dairy. Tuberculous individuals should therefore not be permitted to handle milk. CHAPTER VII DAIRY FARM INSPECTION Tue hygienic qualities of milk depend very largely upon the conditions existing at the source of supply. A knowledge of these conditions can be obtained only by an inspection of the dairy farm. Collecting a sample of milk in the city or town and examining it in the laboratory will disclose certain conditions, and it will usually be cor- rect to infer that the same conditions exist in the entire volume of milk from which the sample was taken. Some of these conditions may be dangerous to the health of the milk consumer, but the milk will have been consumed before they have been discovered. Determining the number of bacteria per c.c. in a sample of milk will fur- nish a good basis for judging the care observed in pro- ducing and handling the milk, especially in regard to cleanliness and cooling, but it will not discover the pres- ence of the bacilli of typhoid fever, tuberculosis, or diph- theria, nor other important pathogenic organisms. Even if it were practicable to subject each sample of milk to the comprehensive examination necessary to discover these organisms, the milk from which the sample was taken would be consumed long before the examination could be completed. It is more rational to guard the milk against contamination at the source than to attempt to discover contaminated milk after it reaches the city and then exclude it from the supply. While it may not be possible to discover the actual contamination of the milk in all cases by inspecting the dairy farm, the conditions which permit or favor con- 126 DAIRY INSPECTION 127 tamination can, with few exceptions, be discovered by a eareful inspection. A proper laboratory examination of the milk in connection with the inspection will generally detect those conditions which may escape discovery at the inspection. The information obtained by inspection will serve as a basis for judging the quality of milk which may be produced, not only on the day of inspection but also thereafter. Moreover, inspection brings a repre- sentative of the health authorities into personal contact with the dairyman, a condition which should make for a better understanding and more sympathy on both sides. It is sometimes asserted that the bacterial testing of milk is more efficient in improving or controlling a milk supply than dairy inspection. This statement, however, will not bear critical examination. ‘The ordinary bac- terial test merely approximates the number of clumps of bacteria present in a very small portion of milk. It does not determine the number of bacteria present, the kind, nor their source. It does not tell whether a high count is due to conditions existing at the dairy farm, during transportation, or at the distributing plant. It does not discover the presence of pathogenic organisms, excepting, perhaps, streptococci, and it does not indicate the source of these latter organisms. On the other hand, inspection of a dairy farm will disclose the physical condition of the cows, the sanitary condition of the premises, the char- acter of the equipment, the methods in use, and the physi- cal condition and proficiency of the dairyman and his employees. Dairy inspection alone will certainly furnish more useful information for judging the hygienic prop- erties of milk than bacterial testing alone. Asan adjunct to dairy inspection, however, bacterial testing and other laboratory methods of examining milk are of great ser- 128 PRINCIPLES AND PRACTICE OF MILK HYGIENE vice. Unless bacterial testing is to be used only to find faults and no assistance is to be offered in correcting them, it must be combined with dairy inspection, Inspection of a dairy farm should include an exami- nation of the following: I. Stable: 1. Exterior, 2. Interior. Il. Cows: 1. Cleanliness. 2. Stage of lactation. 3. Symptoms of disease. LLL. Stable practices: 1. Cleaning the stable. 2. Cleaning the cows. 3. Milking. 4. eeding. 5. Bedding. IV. Milk THlouse: 1. Location. 2. Construction. 3. Apparatus. 4. Water supply. A certain system or routine should be followed in making the inspection so that nothing will be overlooked. It is usually convenient to begin with the stable and then to follow the course of the milk from here to the storage cans or bottles, although the point of beginning will have to be varied to suit the cireumstances. ‘The best time to make an inspection is while the cows are being milked, but, unfortunately, all dairies cannot be visited at this particular time. The inspector should provide himself DAIRY INSPECTION 129 with a suit of thin, washable material to protect his ciothing, and should also wear a close-fitting: cap to pro- tect his hair while ausculting the lungs. Material of blue or a darker color is more desirable than white, because in stables where white suits are not worn by the milkers some of the cows are likely to kick at a stranger wearmg white clothing. The inspection should be carried out as follows: TI. STABLY 1. Exterior —On approaching the stable, the inspector should take note of: (a) "The location of the building with regard to sur- face drainage. It is desirable to have the floor of the stable about eight inches above the surrounding ground and to have the adjoining: ground slope away from the stable. (b) The type of stable and its general construction —whether a bank barn with the stable in the basement and storage space above for feed, or a one-story stable entirely above the ground; also, whether the building is constructed of stone, wood, or cement. Information on these points may be of value later in the inspection m considering the arrangements for lighting: and ventila- tion. (c) Haposure.—The direction in which the windows and doors face is of importance, as it has considerable m- fluence on the temperature and lighting of the interior. When there can be windows and doors on only one side of the stable it is best to have them facing the south. This exposure will permit the morning sun to shine into the stable and will keep out the hot afternoon sun in summer and the cold winds in winter. When the cows stand in a double row the most desirable arrangement 9 130 PRINCIPLES AND PRACTICE OF MILK HYGIENE is to have the windows on the east and west sides with the two rows of cows extending north and south. The win- dows on the west side can be provided with wood shutters to keep out the sun on hot summer afternoons. When the shutters are up the flies will also be less troublesome on that side of the stable. (d) Surroundings.—The location of the manure dump and the direction of the surface drainage from the same should be observed, particularly with relation to the location of the source of the water supply. The accessibility of the manure pile to cows turned out for exercise or being driven into or out of the stable should also be considered. When cows are permitted to wander about in a lot of manure they become very much soiled, especially their legs and udders, and also carry a good deal of dirt into the stable. The proximity of other buildings, especially if used as horse stables, chicken houses, pigpens, etc., should be noted. Buildings used for these purposes, as well as manure piles, are breeding places for flies and are there- fore objectionable when too close to a dairy stable or milk house. Attention should be given to the condition of the barnyard or exercise yard. Note its size and whether or not it is well drained. The condition of the barnyard has a considerable effect upon the cleanliness of the cows and stable. If it is muddy or dirty, some of this material will become attached to the cows and will be carried into the stable, increasing the labor of cleaning the cows and the stable. 2. Interior of the Stable——_In examining the cow stable, the fact should be kept in mind that it is not only a shelter for animals but is also a place where human food is pro- DAIRY INSPECTION 131 duced. Cows in milk should not be kept in the same stable with horses or other animals; they should have a separate stable for their exclusive use. There should be a special stable for parturition and for cows which are not in health. (a) Odor of the Air.—On entering the stable the odor of the air should be noted, since any slight abnor- mality will be more perceptible at this time than later, when the inspector has become accustomed to the atmos- phere. The odor of the air is a good test of the efficiency of the ventilation and also of the degree of cleanliness of the stable, especially in cold weather when the doors and windows are closed and the cows are kept in the stable almost continuously. Abnormal odors in stable air usually originate from two sources: exhalations from the cows and decomposing manure and urine. Condensa- tion of moisture on the walls, ceiling, or windows or the presence of frost is another indication of defective venti- lation. A moist atmosphere assists in the spread of tuber- culosis in a stable. The droplets of infected saliva ex- pelled by tuberculous cattle in the act of coughing float more readily in the stable air when it is saturated with moisture than when it is drier. In most instances cattle are infected with tuberculosis by the inhalation of in- fected air or by the ingestion of infected food or water. Insufficient ventilation has the effect of concentrating any infection in the air of a stable, while ventilation dilutes it. Recent experiments have shown that the harmfulness of insufficient ventilation is not due to a deficiency of oxygen, an excess of carbon dioxide, or the presence of organic poisons in expired air, but to the warmth and moisture of the air in unventilated places and to its lack of movement. A warm, moist atmosphere has a depress- 132 PRINCIPLES AND PRACTICE OF MILK HYGIENE ing effect upon the animal organism. It decreases the working capacity of the muscles and lowers the vaso- motor tone. It also causes a congestion of the nasal mucous membrane, rendering the animal more suscep- tible to respiratory infection. There is also reason to believe that metabolism is depressed. A moderately cool and moderately dry air in motion is the most healthful atmosphere for animal life. Ventilation.—The best system of ventilation for dairy stables is the one devised by the late Prof. F. H. King. Like other systems, it has inlets for the admission of fresh air and outlets Fie. 9.—Showing on the left how an inlet can be placed in a wall already constructed; on the right, how an inlet can be put in a wall being built; and in the centre, an outlet shaft with two openings—one just under the ceiling and one a foot above the floor. for the removal of impure air, but it has two features which are peculiar to it. The inlet flues are bent at a right angle, and the outside opening is lower than the inner one, the purpose being to prevent the escape of air from the stable through the inlets. The outlet flues are built from the floor up and have an opening near the floor as well as one near the ceiling, thus providing a means of drawing air not only from the upper DAIRY INSPECTION 133 part of the stable, but also from the lower. Inlets are placed in all of the outer walls of the stable if possible, with the inside opening just under the ceiling and the outside opening five feet lower (Fig. 9). The number and size of inlets necessary will vary with weather conditions, and it is therefore desirable to have as many as possible and then use as many as may be needed. Weather conditions exert considerable influence on the air in stables ventilated by any system which depends for its opera- tion on natural forces. When the atmosphere is still or moist, the ventilation is often inefficient in stables which under other conditions are well ventilated. A cow requires 59 cubic feet of air per minute and it is estimated that air will pass through a flue at the rate of 290 to 300 feet per minute. The minimum number and size of inlets and of outlets required may therefore be calculated accord- ing to the following formula: } No. cows in stable x 59 , 144 sq. in. = Total cross-sectional area in square inches 300 of inlets and of outlets. By dividing the total cross-sectional area by the number of inlets and of outlets, the cross-sectional area of each inlet and outlet is ascertained. The number of inlets and of outlets will depend upon the size of the stable. Inlets should not be over 12 feet apart; closer if possible. Several outlet flues of moder- ate size in different parts of the stable are preferable to one or two large outlets. Each inlet should be provided with a sliding door or other contrivance by which it can be conveniently opened or closed. The outlet flues should extend from the floor to 6 feet above the highest point of the roof and should be capped with a hood 1 foot above the top. If they cannot be placed where they will not act as obstructions, they may be hinged at the ceiling so that they can be drawn up out of the way temporarily (Fig. 10). Each outlet flue should have two openings into the stable, one just under the ceiling and the other a foot above the floor, both openings being provided with doors which can be readily opened ' Wisconsin Exp. Sta., Bull. No. 266. 134 PRINCIPLES AND PRACTICE OF MILK HYGIENE or closed. ‘The outlet flues must be air-tight and protected against cold in exposed places. The best material for the construction of these flues is galvanized iron (No. 28), 2 x 4 inch lumber being used in the corners and joints. Where the shaft is exposed, the iron should be covered with 7%-inch boards. Outlets may also be constructed of a double layer of tongued and grooved boards with a layer of heavy building paper be- tween. If tin or galvanized iron pipes are used, they should be surrounded by a square wood frame and the interstices filled C1) i i GE Wie i an y sir inant Aare! <—_ Fia. 10.—An ae flue hinged at the ceiling so that it can be drawn up out of the way. in with sawdust. Protection against cold is necessary because the air in the outlet flue must be kept warm, otherwise it will cease to ascend. The ceiling and walls of the stable should be air-tight and should be constructed with a view to preventing the radiation of heat as much as possible. The circulation of air through the stable results from the operation of two factors, called by Professor King aeromotive forces, namely: heat generated by the cattle, and wind. The wind drives air through the inlets on the windward side of the stable and thus increases the air pressure within the stable, as a result of which air is forced out of the stable through the outlets. DAIRY INSPECTION 135 If the wind is very strong, air may also be forced out through the inlets on the leeward side, but ordinarily the right-angled bend in the inlets and the position of the outer opening at a lower level than the inner prevents or retards the escape of air through these inlets. In addition, wind passing over the top of an outlet shaft produces a suction action within the flue, and this draws air out of the stable. The force of this suction action increases with the height of the outlet shaft, because air movement or wind increases in velocity with the distance about the ground. The heat given off by the animals in the stable through the skin and in the respired air warms the stable air around them, expanding it and decreasing its density or weight, which causes it to rise toward the ceiling. Fresh air entering through the inlets, being colder and heavier than the air in the stable, gravi- tates toward the floor. Through the operation of these two currents the stable air and fresh air are mixed, the fresh air is warmed while the stable air is cooled and the moisture it contains is diluted. However, when the respired air is cooled below 81° F., it becomes heavier than fresh air of the same temperature because of the carbon dioxide which it contains and consequently settles toward the floor. For this reason, it is desirable to have the outlet flues arranged to draw air from the lower as well as the upper part of the stable. The expansion of the air in the stable by the animal heat increases the pressure within the stable and this has the effect of forcing air through the outlets; the construction of the inlets prevents air from being forced out through them. 'To obtain satisfactory results, the air in the stable should be about 20° F. warmer than the air outside. The effect of temperature differences on the draft in outlet flues increases with the length of the flue. The resistance encountered by air in passing through inlets and outlets modifies to some extent the effects of wind and heat. It is therefore desirable to have the outlet flues as straight as possible. Cloth Method of Ventilation.—Stables may be ventilated by covering windows with muslin or cheese cloth. Glass windows should be alternated with the cloth-covered windows in order to permit sufficient light to enter the stable. Three square feet 136 PRINCIPLES AND PRACTICE OF MILK HYGIENE of glass and 2 square feet of cloth for each 1000 pounds of animal weight is a good proportion. When the air is still, a stable ventilated by means of muslin-covered windows will not be more than 1 to 3° F. colder than stables in which the King system is used, and there will be 7 to 10 per cent. less humidity in the stable air; but when high winds prevail, the animal heat will be rapidly dissipated and the stable will be colder. If the cloth becomes wet and freezes, ventilation will cease. (b) Cubic Air Space.—This is determined by meas- uring the length and width of the stable, multiplying the length by the width, and then multiplying the result thus obtained by the height of the ceiling. After the total cubic feet of air space has been ascertained in this manner, the stanchions or ties should be counted and the total cubic feet of air space divided by the number of stanchions. The result will be the cubic feet of air space per animal. The number of stanchions or ties should be used for this purpose instead of the number of animals present because this method will give the minimum cubic feet of air space per animal under all conditions. The size of a stable in proportion to the number of animals in it bears an important relation to ventilation. The less air space per animal the more frequently the air in the stable must be changed. The heat given off by animals is only sufficient to warm a certain quantity of air, and if this limit is exceeded the stable will be cold in winter. A stable with insufficient cubic air spaces will also be hot and uncomfortable in summer. It is desirable to have 1 cubic foot of air space for each pound of animal weight, but this amount cannot always be provided because of the cost of building mate- rials and for other reasons. With suitable arrangements for ventilation, 500 to 600 cubic feet of air space per cow DAIRY INSPECTION 137 will answer quite well. A cow requires 59 cubic feet of air per minute, or 8540 cubic feet per hour. ‘To provide this amount for a cow occupying a space of 500 to 600 cubic feet, it would be necessary to entirely change the air in the space occupied by the cow six to seven times per hour. It is estimated that the heat given off by a cow in 24 hours is equal to 76,133 British thermal units, which is sufficient to heat 79,603 cubic feet of dry air from 0° to 50° F. This quantity of air would provide 3316 cubic feet of air per hour, only 224 cubic feet less than the quantity required by the cow.’ It would appear, therefore, that the required amount of fresh air could be admitted to a stable with 500 to 600 cubic feet of air space per cow without lowering the temperature too much, especially since the temperature only rarely falls to 0° F. in the dairy sections in the northern part of the United States. The most comfortable temperature for the dairy cow is from 60° to 65° F., but if the temperature is kept lower by ventilation, say down to 50° F., the cow will not suffer in health and the milk flow will not be reduced, provided exposure to the low temperature be- gins in the autumn and is continuous. Milk cows have been kept through the winter in sheds open to the south with quite satisfactory results. The distribution of the cubic air space is important. If the ceiling is too high, the stable is likely to be cold at the level occupied by the cows, although the upper part may be warm enough. The height of the ceiling should be regulated by the size of the stable. Eight feet is a sufficient height for small stables. In a stable for 12 cows 1 These figures are taken from Prof. F. H. King’s book on ** Ventilation.” 138 PRINCIPLES AND PRACTICE OF MILK HYGINNE the ceiling should not be over 10 feet high; for 80 cows, not over 12 to 15 feet; more than 80 cows, not over 16 feet (Rievel). The length and width of the stable should be such as will provide sufficient floor space to accom- modate the cows comfortably and to make it convenient to milk and care for them. When the cows stand facing’ the centre of the stable, the alley or passageway in back of them should be of sufficient width to permit the passage of aman carrying a pail of milk without the pail touch- ing or coming too near the cows. ‘To meet this require- ment it is necessary for the passageway to be at least 3 feet wide, the milk pail being carried on the side of the milker farthest from the cow, but a width of 5 or 6 feet is much better. A narrow passageway back of the cows makes rt dificult to keep the wall clean. ‘The passageway between two rows of cows standing: tail to tail should be at least 8 feet wide; tt can hardly be wide enough to prevent milk carried ina pail between the cows from be- ing contamiated by the dust dislodged by the switching of the tails. There is also danger of contamination from splashing urine and manure. ‘lo provide 500 to 600 cubic feet of air space per cow the floor space, with a 9-foot ceiling, may be distributed as follows: eed alley Avan kat aieilaitarteliuies A foet WEIS) ele ailaie 144 to 2 feet Platform ..... 415 to 5Y feet [CTL Ac) Se Rg AR a 16 inches Alley in rear of cows 5 to 6 feet The total of these dimensions would be 18 feet. Al- lowing 38% feet for the width of the stall, there would be G3 square feet of floor space for each cow, which, with a DAIRY INSPHCTION L3y ceiling 9 feet high, would provide 567 cubic feet of air space per cow. With the cows standing in two rows, the stable would be 86 feet wide, which is not too wide for it to be well lighted if windows are placed on both sides. It will therefore be seen that the necessary area of floor space to make the cows comfortable and the stable work convenient will also provide a fair amount of cubic air space, (c) Interior Construction.—'Vhe material used in the construction of the ceiling, walls, floor, platform, feed trough, drop or gutter, and stall fittings, their state of repair and their condition in regard to cleanliness should be noted, While defects and deficiencies in stable con- struction may be overcome to a considerable extent by vareful and painstaking’ methods, at the same time a properly constructed and conveniently arranged stable saves labor and therefore encourages the practice of good methods; it also adds to the comfort of the cows and con- sequently increases their productiveness. The ceiling should be tight and smooth, plastered, painted, oiled, or whitewashed, and free from cobwebs. There is no objection to storing hay or fodder above the cow stable if the ceiling is tight. It is better not to have any openings in the ceiling through which hay, fodder or straw may be thrown down into the stable; but if there must be such openings, they should be in front of the cows and not in the rear. The walls should be smooth and clean, It is desirable to have the inner surface of the walls back of the cows finished smooth with cement for at least 4 feet above the floor and covered with an impervious paint from which dirt can be readily removed by washing. Where paint or cement cannot be used, the application of whitewash will 140 PRINCIPLES AND PRACTICE OF MILK HYGIENE improve the conditions. Any woodwork can be treated in the same manner. Whitewashing removes dirt and cobwebs, improves the light, and exerts a disinfectant action. The platform, or the floor of the stall, should be about 8 inches above. the bottom of the drop or gutter and should be smooth, free from cracks or depressions and impervious. All things considered, cement is probably the best material cf which to construct platforms. Cement platforms are objected to on the ground that they are slippery, cold, and hard. If given a rough finish with a wood trowel or by drawing a stiff broom over the surface before the cement is dry, they will not be slippery. A layer of coal tar or pitch about 114 inches below the surface will reduce the conduction of heat from the body of the cow and will therefore make the platform warmer, while the hardness can be overcome to a certain extent by the use of plenty of bedding. Recently, a mixture of two parts of sawdust and one part of cement has been recommended in place of the usual cement mix- ture, the claim being made that it is warmer and is not as slippery. A covering of inch boards is sometimes laid down over the cement to reduce the hardness and cold- ness. Cement floors have several advantages: they are readily cleaned, wear well, and do not absorb urine or liquid manure nor permit these substances to leak through and saturate the earth beneath. Next to cement, the most desirable floor is one of matched planks, with the joints filled with tar. Wood is less of a heat conductor than cement and is not as hard, but it absorbs urine and liquid manure and is liable to crack and form crevices in which manure and other material may lodge and decom- pose; it is also less durable than cement. Cork bricks DAIRY INSPECTION 141 laid on concrete are also used for platforms and floors. It is claimed for them that they combine the good prop- erties of cement and wood and at the same time do not have any of the undesirable properties of those sub- stances. An earth floor is most objectionable. Unless plenty of good absorbent litter is used it is very likely to be wet and dirty; it finally becomes saturated with urine and liquid manure, which decompose and liberate foul-smelling gases. The rear 18 inches of the platform should slope slightly toward the gutter, just sufficient to cause liquids to flow in that direction. 'Too much slope is likely to cause the cow to slip; it also causes the cow to stand down in the gutter and favors prolapse of the vagina and similar troubles. It is desirable to have a depression in the front of the platform °4 inch deep and extending back about 18 inches from the anterior border. 'This will prevent cows from falling on their knees when attempt- ing to rise or when reaching for feed, and will also have a tendency to keep the litter from being pushed toward the rear of the stall (Fig. 11). The length of the platform is important; if too long, the feces are dropped where the cow can lie upon them; if too short, the cow is uncomfortable and stands down in the gutter. The proper length is 444 to 5% feet, differing with the size of the cow. Frequently, where a number of cows stand in a row, the platforms are made 41% feet long at one end with a gradual increase to 51% feet at the other end of the row, thus supplying platforms of different lengths on which the cows can be placed ac- cording to size. The platform for each cow should be 314 to 4 feet wide, depending upon the size of the cow. The width is quite as important as the length, because -84400 JO 1801 UI JOOB pus ‘dorp ro 1944n8 ‘17818 Jo 1009 10 ur10;;u7d ‘reBuGUE JO YBNoI} pooy *AaTIe pee} JO JOOF jo sjaaey pus SUOCISUSUIIp SULMOYS ‘100f 91qB48 Jo WON0G8-B80IQ— "TT ‘D1 SUIT PUNQID AN Vee 96.9009 SG & eee @2 © Gero] PR RAS RA RADE ‘S 1 : ; y Rx : : iB ES 2 3 4 i) t 4 ’ 4 J % it r ; + Gece a EE SUIT /2na7 ES i 101 G SAGE ' : H 1 ' ' 1 t i) () : H (} t 1 LIS + 7,9,/ 9-8 + 9, |x. — 2 —+4—_—_ 9- ¢ bed ¢ Se DAIRY INSPECTION 143 if the stall is too wide and the cow stands diagonally the result will be the same as if the platform was too long. The stall should be constructed with the view of preventing the dropping of manure where the cow can lie down upon it, in so far as this is possible, and thus save labor in keeping the cow clean. Other points to be considered are the comfort of the cow, convenience of cleaning the stall, milking, and feeding, and the cost. The feed trough or manger may be built of wood or cement. Cement is better because it is easier to keep clean. A continuous cement trough, extending in front of a row of cows without any divisions, can also be used for water. In addition, the continuous trough is more conveniently cleaned, but on the other hand it favors the spread of infectious diseases, especially tuberculosis. Feed placed before a tuberculous cow may be contami- nated by infected saliva and material ejected in cough- ing, after which it can be readily obtained by cows in adjoining stalls; the tuberculous cow may also contami- nate the feed of the cows standing on either side, and also of cows standing opposite, and when water is run into the trough infection may be carried from one end of it to the other. On the other hand, separate feed troughs or mangers, although decreasing the danger of infec- tion, increase the labor of cleaning; they also make it necessary to have individual drinking cups or to drive the cows to water outside of the stable. When a herd is regularly tested with tuberculin and the reactors promptly removed, and when the trough is swept and washed daily, the danger of infection from the common feeding trough is greatly reduced. The bottom of the feed trough should be 2 inches higher than the level of the platform. When cows have to reach too far for their 144 PRINCIPLES AND PRACTICE OF MILK HYGIENE feed, the front feet frequently slip backward and the cows are thrown on their knees, causing bruises which often lead to the development of knee tumors. The feed trough should be 18 inches wide and at least 6 inches deep, with the front high enough to prevent feed from being pushed out of it. The gutter or drop should be constructed of cement. Wood or earth gutters cannot be kept clean and free from odor. The gutter should be 16 to 18 inches wide, with an average depth of 8 inches below the level of the platform. It should be deeper at one end than at the other, to give the bottom sufficient slope for drainage, or the entire floor may be sloped and the depth of the gutter remain the same. Sometimes the floor back of the platforms is laid on a level with the bottom of the gutter or 2 or 3 inches above it, thus removing the back wall of the gutter entirely or making it 4 or 5 inches lower than the front wall. This has the advantage: of per- mitting the sun to shine into the gutter when there are windows in the rear of the cows, but it also increases the likelihood of manure being splashed upon the wall; when the back wall of the gutter is lacking entirely there is a tendency for the hind feet of cows to slip backward when they are stepping up onto the platform. Plenty of litter should be kept in the gutter to absorb the urine and thus prevent it from being splashed by droppings or by the cow’s tail when the animal is lymg down and switching at flies. The floor of the gutter sometimes has a %4 inch slope from the front to the rear with the object of raising the toe and increasing the tension upon the posterior tendons when cows stand down in the gutter, the intention being to make the position uncomfortable, but this construction does not always have the desired effect. DAIRY INSPECTION 145 Ties or Stanchions.—From a sanitary standpoint, stanchions or jacks are better than chains because they are more likely to hold the cow in the proper place in the stall to cause the manure to be dropped into the gutter, thus assisting indirectly in keeping the cows clean. The swinging chain-stanchion is also quite comfortable. The best material for stanchions and their supports is metal piping. Stall divisions help to keep the cow in place and thus assist in keeping the platform and the cow clean; they also prevent the cow from treading on the udder or teats of aneighboring cow. Solid, board partitions, extending from the floor upward, are objectionable because they increase the difficulty of keeping the stable clean and interfere with the circulation of air; they may also be in the way of the milker. Wood fittings with flat surfaces and cracks are not as easily kept clean as round, smooth surfaces, and the cracks make disinfection more difficult. Stall divisions consisting of a single piece of metal pipe, extending in a curve from the front post of the stall to the rear of the platform, with a radius of 3 feet, are not open to these objections. Arrangement of the Stalls —When stalls in a stable are placed in two rows, they are arranged with the cows in one row facing those in the other, with the feed alley in the centre between the mangers, and a passageway in the rear between the manure gutter and the side wall; or, the stalls are arranged with the cows in each row facing outward toward the side walls, with a feed alley in front of each row between the manger and the wall and a pass- ageway extending through the middle of the stable be- tween the two rows of cows. Both plans have advan- tages and disadvantages. When the cows stand facing a 10 146 PRINCIPLES AND PRACTICE OF MILK HYGIENE central feed alley, feeding is facilitated and, if there are windows in the side walls, the posterior part of the cow is in the lightest part of the stable, which is a convenience in cleaning the cow and in milking; but the spread of infection is favored because material coughed out by one cow may be deposited in the feed trough of the cow standing opposite in the other row. With the cows fac- ing outward toward the side walls, the cleansing of the stable and the removal of the manure is facilitated and there is less exposure to infection by coughing, but the cleaning of the cow and the milking must be done in the darkest part of the stable and the milk must also be carried between the two rows of cows and is thus exposed to external contamination, especially in the fly season when the cows frequently switch their tails. Maternity and hospital stalls should be provided in another part of the building or in another building. If there are not special stalls for these purposes, cows with vaginal discharge from retained placenta and with other pathological excretions will be stabled in the milking Ime and may infect the milk indirectly. (d) Light.—The cow stable should receive sufficient daylight to make it possible to read ordinary newspaper print in the middle of it. This much light is necessary for the cleaning and the milking of the cows to receive proper attention. Nearly all of the work which must be done in a cow stable can be done better and easier in the light than in the dark. The admission of sunlight into a stable is beneficial in several respects. It lights the stable and exposes dirt, thus assisting in keeping the stable and cows clean; it facilitates careful milking; assists in dry- ing out the stable; supplies some warmth to the stable in winter, and has a disinfectant action. The germicidal DAIRY INSPECTION 147 effect of sunlight is not fully appreciated. Experiments with artificial cultures of various bacteria have shown that direct sunlight is very destructive to germ life, while the action of diffused light, although less powerful, is also quite effective. Tubercle bacilli are killed by direct sun- light in a few hours, while even diffused daylight destroys them in a few days (Koch). Direct sunlight kills anthrax spores in five hours and the bacilli in thirty hours, spores being more susceptible to ff sunlight than bacilli (Ar- f long, Roux). Direct sun- light destroys or decreases the virulence of colon bacilli, the bacilli of fowl cholera and swine erysipelas, and the virus of hog cholera, while diffuse daylight also exerts a similar but less powerful } action (Neumark). | The inspector should | note the location and size of the windows and determine the total square feet of win- § dow surface. He should Fe 12.—Window arranged to act as a fresh also observe whether the air inlet (Wis. Exp. Sta. Bull. No. 266). glass is clean and if other buildings obstruct the en- trance of light. Three to four square feet of win- dow surface for each cow will usually admit sufficient light, provided the windows are properly ‘placed and equally distributed. In cold climates, an excess of win- dow surface may increase the radiation of heat to such an 148 PRINCIPLES AND PRACTICE OF MILK HYGIENE extent as to interfere with ventilation; this can be avoided by constructing double windows, with an air space be- tween. Where cows stand in a double row, a row of windows along each side of the barn is very desirable. The windows may be hinged at the bottom and arranged to open and close by turning a continuous rod; or they may be unattached, as many prefer, and merely rest in a groove in the window sill, being held in place by a peg near the top. If the windows are to be used as inlets for ventilation, the openings formed at either side when the sash is inclined inward at the top should be closed by boards or galvanized iron strips extending inward from the window frame on each side. The galvanized iron shields prevent the wind from entering at the sides and blowing directly upon the cattle (see Fig. 12). The arrangements for artificial lighting should be noted. These are rather important, for much of the work in the stable in winter is done before and after daylight. II. COWS The examination of the cow is one of the most impor- tant parts of dairy inspection. If the cows are not in the stable at the time of the inspector’s visit and if it is not convenient to bring them in, this part of the inspection should be made at a more opportune time, but the inspec- tion of the dairy should not be regarded as completed until the cows are examined. No attempt should be made to examine the cows while they are running free in the pasture or exercise lot, unless each one can be readily caught and handled. 1. Examination for Cleanliness.— Observe the condition of the cows with regard to cleanliness, especially the con- DAIRY INSPECTION 149 dition of the flanks and udder. The condition of the cows in this respect is usually an indication of the care they receive and of the efforts made to keep the milk clean. It is not necessary for the inspector to be present when the work is done in order to determine if the cows are regularly cleaned. When cows are regularly groomed, the posterior quarters are comparatively free from dried manure and the hair coat is smooth and some- what glossy. The hair is also shorter and thinner than on cows which are not regularly brushed. Clipping the hair short on the udder, flanks, buttocks, and tail, and cutting three or four inches off the switch if it touches the floor, is of great assistance in keeping the cows clean, and evidence of clipping is an indication that the cows are regularly groomed. Exfoliations from the skin and par- ticles of dirt are likely to collect in the hollows about the root of the tail and their presence in any great quantity points to carelessness or neglect in cleaning. Fresh manure on the buttocks (point of ischium) is not neces- sarily an indication that the cow was not properly cleaned. These parts are readily soiled if, during defecation, the tail is pressed down on the feces and is subsequently moved from side to side. 2. Stage of Lactation—Examination and inquiry should be made regarding the stage of lactation. The daily milk record, if available, will be of great assistance in discovering cows near the end of lactation. When the milk flow has decreased to a quart (2 pounds) a day or less, the milk is likely to have a salty taste or a strong, cow-like odor and taste, and in many cases the cream will not “butter.” Such cows should be “dried off.” The secretion of fresh cows should be examined for the char- acteristics of colostrum. 150 PRINCIPLES AND PRACTICE OF MILK HYGIENE 3. Examination for Symptoms of Disease.—This exami- nation consists of two parts: (a) General examination and (b) special examination. (@) GENERAL EXAMINATION The general examination is made first, with the cow in the stall. Taking a position in the rear and slightly to one side, the inspector proceeds with the examination in the following order: 1. Attitude—Note the general appearance, the car- riage of the head, position of the ears (erect or hanging), standing position, behavior (quiet or restless). Dullness or depression from fever, also weakness and pain may be discovered in this way. Very sick animals and those with a high fever usually hold the head low, with the ears drooping. In severe vaginitis and metritis, and sometimes in constipation and colic, cows stand with the back arched, head lowered, tail elevated, and legs spread apart. Sometimes cows affected with vaginitis stand a long time in the attitude of urination. An arched back and erect hair, in association with shivering and a cold skin are symptoms of fever, although they are not constant. In dyspnea and sore throat the head is extended. Pain causes. restlessness; soreness of the extremities is indicated by resting the affected limb, or, when more than one limb is affected, by continually shifting the body weight from one leg to another. Cows often lie down during the day, espe- cially after eating, and do not rise on the approach of man; therefore, a recumbent position is of less significance with these animals than in the case of the horse. A disposition to lie down continually may be due to erticular rheumatism or to osteo- malacia. Inability to rise is caused by paralysis (spinal frac- tures), milk fever, and ante and postpartum paralysis. Some- times refusal to rise is due to stubbornness. 2. Skin and Hair.—Observe the condition of the skin and hair and look for swellings, enlargements and irregu- larities of form. DAIRY INSPECTION 151 Rough, bristling, lustreless hair and a dry, stiff skin (hide- bound) indicates unthriftiness or lack of condition, which may be due to disease or improper care. In stables in which the cows are regularly groomed, fresh cows, especially heifers with the first calf, may appear rough and thin in comparison with the other cows for a week or two after they are placed in the milk stable. ‘This condition is due to the effects of parturition and to not being regularly groomed previously ; it must not be con- fused with unthriftiness. When associated with a good appe- tite, unthriftiness and progressive emaciation are indications of chronic disease, frequently of tuberculosis. Emaciation, however, may be due to old age. Mere thinness must not be mistaken for unthriftiness or emaciation; heavy milking cows are often thin. The condition of the skin and hair is a better indication of the actual physical condition than the degree of fleshiness or leanness. Swellings may occur in or beneath the skin (local inflamma- tions, eedemas, abscesses, enlarged lymph glands, actinomycosis, etc.) and suppurating wounds may involve the skin and sub- cutaneous structures. Distension of the left side of the abdomen occurs in impaction and tympanites of the rumen. 3. Vulva, Anus, and Tail—These should be ex- amined for evidences of pathological discharges. Dis- eases of the uterus, vagina, and digestive tract may be discovered in this way. There are certain normal dis- charges from the vulva which must not be mistaken for pathological discharges. A small amount of glassy mucous, frequently blood-stained, is discharged during cestrum; a bloody or grayish albuminous discharge is sometimes seen after breeding, while near the end of pregnancy there is usually observed a glassy mucous dis- charge which is often of a red color. A foul, chocolate-colored or reddish fluid containing frag- ments of tissue is discharged from the vulva following retention of the placenta. In metritis and vaginitis the discharge is either 152 PRINCIPLES AND PRACTICE OF MILK HYGIENE colorless or yellow, red or chocolate color, thin at first and gradually becoming thicker. In chronic metritis the discharge is white, sticky, and odorless, or muco-purulent, purulent, or chocolate-colored and foul-smelling. A slight purulent dis- charge occurs in tuberculosis of the uterus. When the discharge is slight it may be observed only when the cow lies down or its presence may be indicated only by a soiled condition of the tail. The vulva is swollen in metritis and in puerperal septicemia. In tuberculosis of the uterus the vulva is flabby and the broad ligaments are relaxed and sunken. Relaxation of the broad ligaments also occurs in ovarian disease and frequently in aged cows. If defecation does not occur during the examination the character of the bowel discharges may be determined by ex- amining the manure in the gutter or drop and by observing the condition of the tail and buttocks. Soft bowel discharges, if general, may indicate a sudden change in feed, overfeeding, or the feeding of spoiled feed, as well as disease. Dry, hard feces, often of a darker color than normal, are seen in constipation and in severe febrile disease; soft or semi-fluid feces in intestinal catarrh, advanced tuberculosis of the mesenteric lymph glands, pseudo-tuberculosis or Johne’s disease and enteritis ; red, choco- late-colored or black faces in hemorrhagic enteritis and dysen- tery. Blood is present in streaks or clots in hemorrhage of the rectum and bloody discharges occur in anthrax. Coarse par- ticles of food in the feces indicate disturbance of rumination in consequence of impaction, torpidity, or paralysis of the rumen. 4, Respiration.—The rate, rhythm, intensity, and character of the respiratory movements can be deter- mined by observing the movement of the flanks. Rapid breathing is often seen in advanced pulmonary tuber- culosis, but it is not a constant symptom. The rate of respira- tion is increased in other diseases of the respiratory tract, in fever and in painful conditions. An increase in the respiratory rate occurs also immediately after eating, after exercise, and in hot weather. Increase in the intensity or depth of the respira- DAIRY INSPECTION 153 tory movements is a symptom of disease, except when it occurs after exercise. A decrease in the intensity or depth (shallow respiration) is observed in pleurisy and in painful conditions of the chest wall. 5. Udder.—Examine the udder by inspection. This can be done best when the udder is full. Compare the form and size of the different quarters. Look for swell- ing (mastitis), atrophy, furuncles (feed boils), altera- tions of cowpox, etc. 6. A ppetite.—Look into the manger and see if the feed has been eaten and note if the animal is ruminating. 7. Muzzle and Nostrils—Touch the muzzle and determine the degree of temperature and moisture. Ex- amine the nostrils for pathological discharges. The muzzle is dry and sometimes roughened in fever and diarrhea. It is alternately hot and cold in fever, and cold and dry in low conditions endangering life.’ Vesicles occur on the muzzle in foot and mouth disease. A discharge from the nostrils occurs in exudative diseases of the respiratory tract, but in tuberculosis the discharge is frequently not present because the exudate is usually coughed up and swallowed. A nasal discharge may escape notice in cattle because it is generally licked off with the tongue. It is most likely to be seen after coughing. A slight mucous dis- charge is normal. 8. Submazaillary and Peripharyngeal Regions.—At- tempt to palpate the submaxillary, parotid, retropharyn- geal and atlantal lymph glands; they cannot be felt unless enlarged. The submazillary lymph-gland is situated within the pos- terior angle of the lower jaw, between the sternocephalicus (sternomaxillaris) muscle and the submaxillary salivary gland. 154 PRINCIPLES AND PRACTICE OF MILK HYGIENE The subparotid lymph-gland is about 21% inches long, flat and tongue-like in form and is located just under the anterior border of the parotid salivary gland and about 3 inches below the base of the ear. In feeling for this gland press the finger inward and backward in the groove between the posterior border of the lower jaw and the parotid salivary gland. The retropharyngeal lymph-gland, also called the pharyn- geal and superior pharyngeal, is about 2 inches long and is situated on the posterior wall of the pharynx. It can be pal- pated, when enlarged, by pressing the extended fingers inward. from each side toward the median line and as far forward as possible between the muscles of the neck and the larynx. The atlantal or posterior retropharyngeal lymph-gland is situated under the wing of the atlas, partly covered by the upper end of the submaxillary salivary gland. By pressing the fingers inward and upward under the wing of the atlas this gland is forced against the under surface of the wing of the atlas. When any of these glands in cattle are enlarged and firm and not hot or painful, tuberculosis is usually present. En- largement of the retropharyngeal glands may interfere with swallowing and respiration. Actinomycotic tumors may be observed in the submaxillary and peripharyngeal regions as well as in the maxillz and tongue. 9. Cough—tTest each cow for cough by exerting pressure with the fingers on the larynx or first three rings of the trachea, or close both nostrils for about a minute; also grasp the skin over the withers with the fingers of both hands and draw it upward. Take note of any coughing which occurs spontaneously and identify the cow each time. A frequent, chronic cough is one of the most prominent symptoms of pulmonary tuberculosis. If a cow can be made to cough by pinching the larynx or the adjoining rings of the trachea, or by closing the nostrils, it is an indication of disease of the respiratory tract. Cough can usually be induced in this DAIRY INSPECTION 155 way in advanced tuberculosis of the lungs; if the cough is low, weak, and moist, it is especially suspicious. Old cows are not infrequently affected with pulmonary emphysema, and a short, dry cough may be readily induced in such animals; but even a cough of this character is suspicious of tuberculosis. A cow in health may cough as a result of inhaling dust, cold air, or irri- tating gases, but the cough is not frequent or chronic. Cough in cattle is softer, hollow (toneless), and more prolonged than in the horse. If drawing the skin up over the withers produces cough, it is an indication of an irritated condition of the lungs or pleura. 10. Lungs.—The lungs should be examined by aus- cultation. In doubtful cases, closing the nostrils for a short time or exercise will render the sounds more audible. Exaggeration of the vesicular murmur (when not due to exercise) and the presence of the bronchial sound, rales, or vague sounds are evidences of disease of the bronchi or lungs. Friction sounds occur in pleuritis (fibrinous). In tuberculosis, especially after exercise, the vesicular murmur may be exagger- ated and rough, and rales and vague sounds may be heard. ‘The disease may exist, however, when no abnormal sounds can be detected. In old cows sibilant rales may be heard because of the presence of pulmonary emphysema. 11. Prescapular and Precrural Lymph-glands.— The precrural glands can be palpated whether normal or enlarged, but the prescapular glands cannot be felt unless they are enlarged. The prescapular lymph-gland, also called the superficial cervical, is situated beneath a layer of muscular tissue at the anterior border of the shoulder, a little above the shoulder joint. The precrural lymph-gland is situated in the flank, just under the skin, at the anterior border of the tensor fasciz 156 PRINCIPLES AND PRACTICE OF MILK HYGIENE late muscle. Normally, it is about 1 inch in width and 4 to 6 inches long. When these glands are enlarged, firm and not hot or painful, they are usually tuberculous. The lymph-glands are also en- larged in leukemia and pseudoleukemia, but in these diseases all of the superficial lymph-glands on both sides of the body are similarly affected. 12. Complete the Examination of the Udder and Examine the Supramammary Lymph-glands.—Inspect the skin of the udder and teats for furuncles, ulcers, symptoms of cowpox, etc. Inspect the opening of the teat canal for scabs. Palpate the udder. This is done most satisfactorily when the udder is empty. Beginning with the inferior extremity of the teat and passing upward, palpate suc- cessively the teat canal, the milk cistern, the gland tissue and the supramammary lymph-glands. Note the tem- perature of the parts and look for symptoms of acute inflammation, induration, and nodules. By rolling the teat between the fingers, thickening of the mucous mem- brane of the cistern and nodular formations in the walls of the cistern and teat canal can be detected. In palpat- ing the udder, pass one hand up between the two halves of the organ, place the other hand on the external surface and then, beginning at the posterior or anterior extremity, slowly work the udder tissue between the fingers, search- ing for indurations, retention cysts, etc. Draw milk from each quarter into the palm of the hand and examine it for color, consistency, flakes, clots, etc. In doubtful cases collect a sample for further examination. Press the end of the teat to see if any mucus or pus can be squeezed out of the teat canal. Ob- serve if there is any difficulty in expressing the milk from DAIRY INSPECTION 157 the teat and if the stream is split or deflected from the normal direction. Palpate the supramammary lymph-glands. Stand- ing in the rear of the cow, press the hand forward along the upper and posterior margin of the udder, with the thumb on one side of the median line and the fingers on the other, and grasp the glands by bringing the fingers and thumb together. Ordinarily, these glands are about 2 inches in diameter, but in heavy milkers they may be larger. Pronounced swelling, excessive heat, and pain in one or more quarters of the udder, with marked changes in the milk, are symptoms of parenchymatous mastitis. Firm nodules which are neither hot nor painful, or a rather diffuse induration which is painless and without heat, in one or both posterior quarters, with enlargement of the supramam- mary lymph-glands, are symptoms of tuberculosis of the udder. There is no apparent alteration of the milk during the first stages of the disease. Indurated areas of greater or less extent result also from parenchymatous and catarrhal mastitis, but they are not accompanied by enlargement of the lymph-glands, except in the acute stage. Enlargement of the supramammary lymph-glands is asso- ciated with tuberculosis of the udder and also occurs during acute mastitis. These glands may be enlarged as a result of tuberculous infection when no symptoms of the disease are apparent in the udder. Difficulty in expressing milk from the teat and deflection or division of the milk stream are early symptoms of catarrhal mastitis. If pus or mucus can be squeezed out of the teat canal, catarrhal mastitis is present. A scab may be found over the opening of the teat canal when this disease exists, although clots or flakes of dried milk are sometimes present when the udder is normal except for some defect in the sphincter ap- paratus of the teat. The milk may appear unaltered or show only slight changes when these symptoms are present. 158 PRINCIPLES AND PRACTICE OF MILK HYGIENE A thick cord-like induration, about the thickness of a lead pencil, extending vertically through the middle of the teat, is a symptom of catarrhal mastitis; also nodular indurations in the walls of the teat canal and milk cistern. Only slight alterations may be present in the milk, or none at all. Atrophy is usually a symptom of an existing or previously existing catarrhal mastitis. Milk from the affected quarter may contain the organism responsible for the condition even when it shows no perceptible changes. (For the changes in milk occurring during udder disease see pages 105-110.) Firm, nodular swellings, not hot or painful, situated in the superficial parts of the udder tissue, which are not movable and which can be reduced by strong pressure, are retention cysts, formed by the blocking of the milk ducts. (b) SPECIAL EXAMINATION The character of the special examination will depend upon the information obtained during the general examination. If fever is suspected the temperature should be taken with a thermometer and an examination made for the other symptoms of fever (chill; irregularity of the sur- face temperature, especially of the extremities; accelera- ation of the pulse and respiration, loss of appetite, depres- sion, albuminuria). In cattle the increase in temperature as shown by the thermometer does not always correspond to the degree of fever indicated by the other symptoms. When thoracic disease is suspected the chest wall should be percussed. Areas of hepatization and solidifi- cation may thus be discovered. The area of the lungs of cattle which can be percussed is limited, however, and unfortunately tubercular solidifications usually occur below this area. Percussion may reveal painful condi- tions of the lungs and pleura and may also produce cough. DAIRY INSPECTION 159 If tuberculosis of the uterus is suspected, the sub- sacral, sublumbar and internal inguinal lymph-glands should be palpated per rectum. These glands are en- larged, firm, and often nodular when the uterus is tuber- culous. The mesenteric lymph-glands can also be examined in the same manner. Further information regarding internal conditions can be obtained by examining the sclerotic conjunctiva and the mucous membrane of the cheeks. These mem- branes are pale in tuberculosis and in other chronic debili- tating conditions which lead to anemia and hydremia; bluish-red (cyanotic) in febrile, respiratory, and cardiac diseases and in conditions which interfere with the en- trance of air into the lungs; brick-red to dark red, with the blood-vessels injected, in hyperemia and inflamma- tion of the brain and in conditions which interfere with the return of venous blood from the head to the heart (pul- monary emphysema, organic heart disease and cardiac weakness) ; ecchymotic in anthrax, severe anemia and pernicious anemia, and yellow in icterus. When symptoms suspicious of tuberculosis are present and no definite conclusion can be reached, the cow should be tested with tuberculin. When catarrhal mastitis is suspected and a definite diagnosis cannot be made, the milk should be examined by the catalase, leucocyte, or alcohol tests and micro- scopically, for streptococci. III STABLE PRACTICES Attention should be given to the manner in which the stable is cleaned, when and how the cows are cleaned, the methods of milking and of caring for the milk, the time of feeding, character of the feed, and when the litter is put down and the material used. 160 PRINCIPLES AND PRACTICE OF MILK HYGIENE 1. Method of Cleaning the Stable—lIf manure is allowed to collect in the stable the cows will become soiled and odors of decomposing manure and urine will per- meate the stable air and may be absorbed by the milk. The manure should be removed twice daily if possible, being taken out before each milking. It is necessary to complete this work at least an hour before the cows are milked in order to allow time for the air to become free from dust and odor before milking is begun. When the cows must be milked very early in the morning it is not always practicable to get the manure out of the stable an hour before milking time, and in such cases it is better to remove it after the cows are milked and fed. Miulk of good quality can be produced under these conditions. If the manure is not hauled immediately to the fields, it should be stored as far away from the stable as possible. The stable and its immediate surroundings should be kept as free as possible from manure and other decaying or- ganic matter because flies breed in such material. House- flies may travel considerable distances from where they breed, flights of one-quarter to nearly a mile having been observed, but, as they seem to be attracted by odors, keep- ing the stable clean will in a measure serve as a protec- tion when flies are permitted to breed in the neighbor- hood. After the manure has been taken out, the litter on the rear end of the platform, which is usually soiled, should be swept into the gutter and given an opportunity to absorb any liquid which may be present. When the cows have been cleaned, the rear end of the platforms and the floor back of the gutter should be sprinkled with water and swept clean. In some stables the platforms and floors are again sprinkled after sweeping. This is DAIRY INSPECTION 161 done to keep the atmosphere as free from dust as possible. In other stables land plaster is spread in a thin layer on the floor and in the gutter to act as an absorbent. This is especially desirable when the floor is of wood or earth. The use of land plaster also seems to have the effect of reducing the number of flies. Although the inspector cannot be present during all of these operations, he can make a fairly accurate estimate of how thoroughly the work is done by observing the condition of the stable at the time of his visit. Dirt which has been permitted to remain for some time can be easily distinguished from fresh dirt. 'The wall in the rear of the cows and the corners formed where the walls, posts, and stall divisions join the floor should be especially examined. The pres- ence of cobwebs on the walls, ceiling, or other places is an evidence of infrequent sweeping. Flies.—The presence of flies in large numbers in and about a cow stable is objectionable for several reasons. The flies worry the cows and reduce the milk production, while the move- ments of the cows in their efforts to protect themselves from the insects interfere with milking and are also likely to dislodge dirt from the body of the cow; some of this dirt may fall into the milk pail. The common house-fly (Musca domestica) is especially objectionable. It feeds upon all kinds of organic matter, including human excrement, and becomes contaminated with numerous bacteria. A single fly may carry over a million germs on the surface of its body. When it feeds upon milk or crawls or falls into milk vessels, many of these bacteria are transferred to the milk. Typhoid bacilli may be carried from infected fecal matter to milk in this way. The small, black cow- fly or horn-fly (Hematobia serrata, Lyperosia irritans L.) and the stable-fly or biting-fly (Stomozxys calcitrans) disturb the cow more than the house-fly, because they are biting or blood- sucking insects; but they do not as a rule invade the milk vessels or the milk. aut 162 PRINCIPLES AND PRACTICE OF MILK HYGIENE Various methods are used to reduce the number of flies in cow stables and in milk-houses. ‘The cows are sprayed or brushed with mixtures of drugs or chemicals known as fly. repellents. Sometimes sheets of fly-paper are placed about the buildings. Miulk-houses are very often screened and more rarely stables are also screened. Fly repellents are only temporary in their action and they are often objectionable on account of their odor. Fly-paper is unsightly and inefficient. Fly-traps are more useful. Screening milk-houses gives good results and is desirable in all cases, but screening stables is not satisfactory. Since the doors must be opened frequently and sometimes for long periods to remove manure, to take in the feed, and to drive the cows in and out, there is abundant opportunity for flies to enter. The cow-fly or horn-fly is carried in on the cows. All of these methods are fundamentally defective because none of them prevents the breeding of flies. The most rational method of attacking the fly problem is to remove or abolish, in so far as is possible, the conditions which favor the development of the insects. To do this intelligently it is necessary to consider their habits and life history. Three varieties of flies are commonly found in cow stables: the common house-fly, the cow-fly or horn-fly, and the stable- fly or biting-fly. The house-fly and cow-fly are usually the most numerous, but in some sections of the country, especially in the grain belt, the stable-fly is present in large numbers. ‘The dif- ferent varieties can usually be distinguished by the part of the cow which they occupy and by their sitting position. The small, black cow-fly is generally located upon the back and sides of the cow, and in rainy weather on the under parts of the body, sitting with the head downward. The stable-fly usually occupies the lower parts of the legs and nearly always sits with the head upward, while the house-fly may be found on any part of the cow and may sit in any position, but never with the head pressed into the hair as though feeding. The stable-fly is about the same size as the house-fly but has a more plump appearance and has longitudinal lines on the thorax and several dark spots on the abdomen. The horn-fly is smaller and black. The house-fly seems to prefer to deposit its eggs in horse DAIRY INSPECTION 16% manure, but when this is not available the eggs are deposited in other organic material. The heat generated by the decom- position processes which occur in such material hatches the larve or maggots from the eggs in one day. ‘The larve develop into pup# in 4 to 5 days and flies emerge 3 to 4 days later. The time from the egg to the fly is 8 to 10 days. It is recommended that manure be removed to the fields at intervals of seven days or less to prevent the development of the flies, but this plan will be effective only when the manure is stored in a receptacle which has a tight bottom, because the larve or maggots frequently burrow into the earth to pupate. The larve also bury themselves in the same manner in an earth stable floor. This propensity of the larve to migrate has been made use of to trap them by Hutchinson, who constructed a trap consisting of a raised platform with a shallow cement tank beneath it. The platform is made of wood strips 114 inches thick and 1 inch wide, laid 1 inch apart. The manure is piled compactly on the platform, each day’s addition being moistened with water. When the larve are hatched they migrate down- ward and fall through the spaces in the platform into the water in the tank below, where they are drowned, Numerous experiments have been made to discover a sub- stance which when mixed with horse manure would destroy the larve of the house-fly without affecting the fertilizing value of the manure. Naturally, the chemical fertilizers were tested, but it was found that acid phosphate and ground phosphate rock will not kill the larve, while kainit (KCl and MgSO,) possesses only slight larvecidal action. In several experiments, Cook and Hutchinson found that calcium cyanamid (CaCN,), a substance frequently incorporated in commercial fertilizers to furnish nitrogen, apparently destroyed about 98 per cent. of the larve when applied to manure at the rate of 14 pound to the bushel with an equal quantity of acid phosphate. The cost of this treatment is 1.8 cents per bushel of manure, but the fertilizing value of the manure is considerably increased, so that the actual cost is much less. A portion of the acid phosphate may he re- placed with kainit without affecting the larvxcidal effect and the mixture will then contain all the essentia] elements of plant food. Unfortunately, calcium cyanamid can be purchased only in car- 164 PRINCIPLES AND PRACTICE OF MILK HYGIENE load lots at the present time, but if a demand is created it will no doubt be available in smaller quantities. In the commercial fertilizers it is usually converted into urea, ammonia, etc. Of the various substances tested, the most satisfactory results were obtained with powdered hellebore and borax. One-half pound of powdered hellebore is mixed with 10 gallons of water and allowed to stand 24 hours. This quantity is sufficient to treat 10 cubic feet (8 bushels) of manure, being applied with a sprinkler. The borax is applied with a flour-sifter, especially around the edges of the manure heap, and water is then sprinkled over it; about 1 ounce of borax and 21% to 3 quarts of water are used to each cubic footof manure. Floors, crevices, and refuse may be treated in the same manner with either hellebore or borax. Borax is perhaps a little more effective as a larvecide than hellebore, but the latter is not at all injurious to the manure nor to crops while borax in excessive quantity interferes with plant growth. Manure treated with borax as above may be applied in any quantity up to 15 tons per acre without injuring the crops, except in the case of leguminous plants. When borax- treated manure is used to grow leguminous plants, it should be mixed with untreated manure. The effect of the repeated appli- cation of borax-treated manure has not been determined. The cost of treating manure with powdered hellebore is a little over 1% cent per bushel, while the expense of the borax treatment is a little less than 14 cent per bushel. The cow-fly or horn-fly lays its eggs in fresh cow manure. The larve are hatched in 24 hours and develop into pupz in 5 days. The pupe burrow into the ground and flies emerge in 8 days, the time from the egg to the fly being 14 days. These flies feed upon the blood of the cow and are therefore not likely to get into the milk or milk vessels. In biting through the skin of the cow to obtain food, they cause the animal con- siderable discomfort. When driven off the body of the cow, they fly only a short distance away and then immediately return, so that, while feeding, they are a continual torment. Fly repellents are used to protect the cow from the attacks of these insects. A mixture of one part of oil of tar and nine parts of cotton-seed oil or crude Beaumont oil, applied daily DAIRY INSPECTION 165 with a spray pump or syringe, is an effective and safe repellent. The following mixture, it is claimed, will act effectively for one week: Soap, 1 pound; water, 4 gallons; crude petroleum, 1 gallon, and powdered naphthalene, 4 ounces. The soap is shaved into thin slices and dissolved in the water by heating; the naphthalene is dissolved in the crude oil. The two solu- tions are mixed by stirring vigorously or churning for 15 minutes. The mixture is stirred thoroughly each time before using and is applied to the cows with a brush once or twice weekly. While fly repellents afford the cow temporary relief from the biting flies, they are of no value in the control or eradication of the flies. Hellebore and borax have not been tested on the larve of the cow-fly, but it is very probable that they would be as destructive to these larve as to those of the house-fly. When cows are kept in the stable, with occasional liberty in an exercise yard, the breeding of cow-flies can be prevented by removing the manure from the stable and yard to the fields daily, or if it is stored in the vicinity of the stable, by removing it to the fields at intervals of not less than 12 days, provided the floor of the stable and the floor of the dung-stead are so constructed that the pupz cannot burrow into the ground. When cows are pastured it is not practicable to control the breeding of cow-flies. The manure dropped in the pasture fur- nishes ideal breeding conditions. When the flies emerge they take up a position on the body of the cow, where they feed and rest, and are carried into the stable by the cow. The stable-fly breeds in horse manure and in decaying grass and straw heaps; also in cow droppings which have become dry and disintegrated, and in ensilage. Eggs deposited in these substances hatch out larve in 1 to 3 days. The larve develop into pupe in 11 to 30 days or more, and the flies emerge in 6 to 20 days, the time from the egg to the fly being 18 to 53 days and upwards. The stable-fly feeds on the blood of cows and other domestic animals, and also bites man. Unlike the house-fly, it is not likely to infect milk with bacteria, since it does not feed upon that substance. 166 PRINCIPLES AND PRACTICE OF MILK HYGIENE 2. Cleaning the Cows.—The body surface of the cow may be soiled with dirt and manure when the animal lies down, dust settles on the skin from the air, and dead epidermal cells and hair are cast off from the skin. This material is very rich in bacteria and, if not removed, some of it will be dislodged during milking and may fall into the milk pail. The manure contains numerous gas-form- ing and putrefactive bacteria and is therefore especially objectionable. Dry dirt and manure should be loosened with a curry-comb and then brushed out with a stiff brush, which will also remove loose hairs and epidermal cells. If the dirt or manure is not dry it must be washed off with a clean cloth and water. The addition of 1 to 2 per cent. of washing soda (a Mason jar lid full to a 12 quart bucket) is of great assistance. White hair is likely to show a stain after the dirt has been washed off and this must not be mistaken for dirt. No dust can be rubbed out of an area that is only stained. In cleaning the cows special attention should be given to the udder, flanks, external surface of the thighs and the switch. In some dairies the switch is washed at short intervals. Keeping the hair clipped short on these parts and on the buttocks will facilitate the work of cleaning. It is advisable to have the switch clear the ground by about 4 inches, but there is some objection to cutting the switch of pure-bred COWS. After the udder has been brushed dry it should be wiped with a damp cloth. The cloth and water should be clean at the start and the water should be changed as soon as it becomes soiled. Ordinarily, a bucket of clean water is required for every eight cows. In high-class dairies a small damp towel is used for each cow; each towel is used only once and is then washed and sterilized. DAIRY INSPECTION 167 The brushing should be finished a half hour before milk- ing, to allow time for the dust to settle from the air of the stable, but the udder should be wiped just before milking is begun. If the udder is brushed immediately before milking the number of bacteria in the milk will be about doubled. The practice indulged in by some milkers of attempting to clean the udder by wiping it with the hand after sitting down to milk is not a good one, as it dislodges a lot of loose hair, epithelial cells and particles of dirt which may fall into the milk pail. The purpose in wiping the udder with a damp cloth is to moisten any loose dirt, hair, etc., that may remain after brushing and thus prevent these particles from falling into the milk. The number of bacteria dislodged from apparently clean udders by the process of milking is reduced about two-thirds by dampening the surface of the udder. ‘T'oo much water should not be used, as any excess will run off the end of the teat and may drop into the milk pail, while, in winter, the exposure of a wet udder to cold air is very likely to cause congestion and cracking of the skin, especially at the base of the teats and on the teats, and may also cause catarrhal mastitis. Washing the udder, unless it is afterward rubbed dry, is not as effective in keeping dirt and bacteria out of milk as is wiping it with a damp cloth after dry brushing. The best results ‘are obtained by wiping the udder with a cloth dampened with a 2 per cent. solution of washing soda after it has been cleaned by brushing, and then anointing it with a small quantity of vaseline. As much vaseline as can be taken up on the end of the finger is rubbed over the palms of the hands, which are then passed lightly over the udder. This method takes less time than washing 168 PRINCIPLES AND PRACTICE OF MILK HYGIENE the udder, while the skin covering the teats remains soft and pliable and there is an entire absence of cracks and sores, even in winter. It is sometimes stated that dampening or washing the udder irritates the skin, causing it to swell and crack, and that it decreases the milk flow, but this is not entirely correct. The udder will suffer no injury whatever unless too much water is used and the organ is exposed to cold air in a wet condition. ‘There may be a decrease in the milk secretion when a cow is subjected to the process for the first time, but the milk flow returns to normal in a few days and very frequently it is increased. ‘The mas- sage which accompanies the brushing and the wiping or washing favors the flow of blood to the udder and usually increases the secretion of milk. Udders which are kept clean are affected with disease less frequently than dirty udders. As a general rule, cows will produce more milk when kept clean and comfortable than when they are kept otherwise. Therefore cleaning the cows not only assists in keeping dirt and bacteria out of the milk but usually also increases the milk production. After the cows have been cleaned they should be fastened so that they cannot lie down before they are milked. 3. Methods of Milking.—The condition of the milker as regards health and cleanliness should receive the atten- tion of the inspector. No one should be permitted to milk cows or handle milk in any way who is affected with any infectious disease, especially typhoid fever, diph- theria, and scarlet fever, or who has been in contact with persons affected with any of these diseases. Persons affected with tuberculosis, syphilis, severe diarrhcea, suppurating sores on exposed surfaces, or any throat DAIRY INSPECTION 169 disease should also be debarred from employment on a dairy farm. The milker should have special clothing to wear while milking. Considerable dust and dirt collects on the outer surface of clothing worn while cleaning the cows and stable or in doing farmwork, especially if it is made of material with a soft, rough finish, and a good deal of this dirt may drop off into the milk pail during milking. A clean blouse, overalls, and a cap should therefore be put on before beginning to milk. These should be made of washable material with a smooth, hard, finish like duck, linen, or drilling. White linen or duck is best. One or two suits a week in winter and two or three in summer will be required in order to have a reasonably clean suit at all times. An apron or a pair of overalls with a bib is sometimes used because they are easier to put on and off; but they do not cover the shoulders and arms, the parts from which dirt is most likely to be dislodged in milking. Before beginning to milk, the milker should wash his hands thoroughly, using soap, water and a nail brush, and dry them carefully with a clean towel. After doing so, he should not touch anything but the teats of the cow, milk pail, and milk stool. The inspector should note what facilities are provided for washing and drying the hands. When the milking of a cow is finished, the pail should be carried to the weigh room and the milk weighed and emptied, the weight of the milk being recorded on the milk record opposite the name or number of the cow. In passing in the rear of the cows, the milk pail should be carried on the side of the body furthest away from the cows; covered-top pails should be carried with the open- 170 PRINCIPLES AND PRACTICE OF MILK HYGIENE ing on the opposite side from the body. This will protect the milk from contamination by cows switching the tail, splashing of manure or urine, and dirt falling from the clothing of the milker. The milker should wash his hands again before milking another cow and should dry them well on a clean towel. Small, individual towels, about 10 x 10 inches, which can be used once and then thrown aside for washing, are much more desirable than a large towel used in common by several milkers. Soiled hands are a prolific source of bacteria in milk. As many as 45,000,000 bacteria have been found on one hand of a farm laborer. Washing and drying the hands will reduce the number of bacteria 75 per cent. or more, and also decrease the danger from chronic typhoid bacilli carriers. Experiments indicate that careful drying is quite as important as thorough washing, fewer organisms remaining after careful drying than when the hands are rinsed in an antiseptic solution after washing and are not carefully dried. Milking should be done with dry hands. When the hands are wet the moisture assists in loosening the epi- dermal cells and dirt from the surface of the teat, and this material gradually moves down to the end of the teat and drops off into the milk pail. The practice of wetting the hands with milk when beginning to milk is to be con- demned because this milk, after being mixed with the dirt on the teats, drops off into the pail. Sometimes dairymen claim that it is sufficient to wash the hands before beginning to milk, saying that if the udders are clean the hands will not become soiled. This would be true if the udders were bacteriologically clean and if the milker did not touch anything but the clean teats of the udder. But the milker sometimes touches DAIRY INSPECTION 171 other parts of the cow in pushing or striking the animal to cause it to stand over in the stall and in protecting himself against a switching tail. In addition, the milk bucket is often rested on the floor and the bottom subse- quently grasped in emptying it, thus soiling the fingers with material from the floor. The milking stool may be another source of contamination for the hands. It should Fie. 13.—Open or uncovered pail. Fra, 14.—Covered-top pail with opening nearly horizontal (with strainer attached). therefore be kept clean and it is best to use one made of metal. The milk should be drawn without jerking the teats, as this dislodges dirt and bacteria which are liable to fall into the milk. “ Stripping” the teats is also objection- able for the same reason. ‘The first few streams of milk (fore-milk) from each quarter should be drawn into a separate vessel, as this milk washes out the milk cistern and teat canal and contains a greater number of bacteria than the milk subsequently drawn from the udder. The 172 PRINCIPLES AND PRACTICE OF MILK HYGIENE fore-milk from a normal udder usually contains from 0 to 500 bacteria per c.c., mostly udder cocci. Sometimes more may be present, but when the number exceeds 5000 per c.c. the udder is infested with mastitis organ- isms, usually streptococci. ‘The fore-milk should not be milked out upon the floor or litter as this supplies condi- tions which are favorable to the growth of bacteria. The type of milk pail has a very pronounced influence on the bacterial content of milk. The larger and more horizontal the opening of the pail the greater the opportunity for contamination. There are two types: The open or uncovered pail and the covered-top pail (Figs. 18, 14, and 15). The top of the open pail is entirely un- protected and is about 12 inches in diameter, while the covered-top pail has an opening only 7 inches in diameter, the remainder of the top being covered. The smaller opening, of course, offers much less Al opportunity for dirt to fall into the 5... 15 Coversd-top pail with milk. It is more difficult to milk Fy oot into the covered-top pail than into the open pail, especi- ally at first, but this is largely overcome by practice. There are two varieties of covered-top pails: One with the opening vertical and protected by a hood and the other with the opening more or less horizontal (Figs. 14 and 15). The pail with the vertical opening is prob- ably somewhat more difficult to milk into than the pail with the horizontal opening, but it affords a much greater DAIRY INSPECTION 173 protection against the contamination of the milk than the pail with the horizontal opening, even when the latter contains a cheese-cloth and wire-gauze strainer. Some varieties of pails in which strainers are used have a spout on the side so that they can be emptied without removing the strainer. ‘There is one type of pail which has no opening in the top, but a spout extending from the side ae wana athe aaeinericciai Severed iwivave\aborseioth auaiuar)y “ty ait il) has a funnel in the end to receive the milk. The milker sits on the pail and milks into the funnel. When the pail is to be emptied the furmnel is removed and the milk is poured out of the spout. Pails with several parts are not as easily kept clean as the other kind. Every addi- tional piece of apparatus not only increases the work of cleaning but also provides another possible medium for the conveyance of bacteria to milk. Strainers of cheese cloth and wire gauze cannot be 174 PRINCIPLES AND PRACTICE OF MILK HYGIENE depended upon to protect milk from contamination. They do not keep out bacteria, but hold back only the larger particles of dirt. Some of these particles are sub- sequently dissolved by milk and carried through the strainer, while bacteria are washed off of the insoluble particles remaining on the strainer. It is also difficult to clean strainers of this kind thoroughly. Particles of dirt become entangled in the meshes of the wire gauze, especially at the periphery where it is soldered to the tin, and it is difficult to remove them, while the cheese cloth requires much care in cleaning. It should be rinsed in cold water, washed in hot water containing two per cent. of soda, again rinsed in cold water and then wrapped in a clean cloth and sterilized in a steam chest. If a steam chest is not available, it should be put into a thick paper sack and placed in a stove oven and kept there until the sack begins to scorch. A strainer composed of a thin layer of absorbent cotton is much more effective and it can be thrown away after being used and thus save the labor of cleaning. Some of the bacteria are apparently enmeshed in the cotton and kept out of the milk. The use of a cotton strainer has reduced the bacterial content of the milk nearly one-third in some tests. Coarse cot- ton-flannel and turkish toweling are also used for strain- ers, but they are no more effective than cheese cloth. Bacteria cannot be kept out of milk by strainers nor can they be removed by these contrivances after they have entered the milk. The coarse particles of dirt may be strained out, but the most objectionable part of the dirt the bacteria, will remain. Much more satisfactory results will be obtained by cleanliness and care in milking and in the subsequent handling of the milk. In some receiving stations and distributing plants, DAIRY INSPECTION 175 milk is run through a machine known as a clarifier, in which the milk is centrifugalized and the heavier sub- stances, such as dirt particles, cells, and some of the bac- teria, separated from it. The process is known as clari- fication. When determined by the plate method, the number of bacteria is frequently greater after clarifica- tion than before, but this increase is probably due to the breaking up of clumps of organisms by the centrifugali- zation. Some of the bacteria are removed from the milk since the sludge or residue remaining in the clarifier contains bacteria in considerable numbers. The per- centage removed cannot be very great, however, because the milk is exposed to the separating action for only a short time. The sludge or residue is composed very largely of the amorphous substances normally present in milk, the remainder consisting of bacteria, cells, hair, and particles of dirt. If clarified milk is subsequently centri- fugalized for three minutes at 3000 revolutions per min- ute, sediment will be deposited, showing that all of the sediment is not removed by clarification. All gross sus- pended dirt, such as hairs, dust particles, ete., are, how- ever, removed by the clarifier, and for this purpose it has many advantages over strainers. But milk containing pathogenic organisms is no cleaner from a hygienic standpoint after clarification than before (Bahlman, Hammer). 4, Feeding.—The cows should not be fed immedi- ately before milking. When hay or other dry fodder is brought into the stable and distributed around among the cows, more or less dust is liberated. This dust con- tains numbers of bacteria, principally peptonizers, and if milking is done while it is floating about in the stable air some of these organisms will get into the milk. If 176 PRINCIPLES AND PRACTICE OF MILK HYGIENE the hay or fodder is thrown down directly into the stable from a loft above, the quantity of dust set free in the stable air is much greater than when it is thrown down into a passageway outside of the stable. Feeding meal or ground grain immediately before milking is also objec- tionable, and for the same reason. It is not necessary to feed cows before milking to keep them quiet during milk- ing; they soon become accustomed to being fed after milking. The investigations of Ruehle and Kulp’ indicate that under ordinary conditions dust in the stable air is not nearly as much concerned in the bacterial contamination of milk as has been generally believed, but as it is only necessary to perform the several stable operations in a certain order, and does not require additional labor, to protect milk against this source of contamination it is advisable to take this precaution, especially since un- usual conditions which will increase the infection from this source are likely to prevail at times. The feeding of ensilage fills the air of the stable for a time with the odor characteristic of this substance, and if milking is done during this period the odor and taste of the milk is likely to be tainted. This is likewise true of cabbage and rape, and also of beets, turnips, rutabagas and carrots, and their tops (see page 29). Odors in the stable are very quickly absorbed by milk, especially when it 1s Warm. Sudden changes of feed and overfeeding should be avoided. A sudden change from dry to green feed will produce diarrhoea. Old and highly acid ensilage and sometimes overfeeding will have the same effect. Indi- 1 Geneva, N. Y., Expt. Sta. Bull. No. 409. DAIRY INSPECTION 177 vidual milk from cows in this condition contains prop- erties which cause digestive and intestinal disturbances in infants; when sufficiently diluted with milk from cows in normal condition, it is not likely to have this effect. The presence of diarrhoea also increases the difficulty of producing clean milk. No grain, meal, or fodder that is musty, mouldy, or otherwise unsound should be fed to milch cows. Diarrhoea has been observed in persons ingesting milk from cows receiving feed of this kind. It has been assumed that the diarrhoea was due to substances formed in the feed being excreted in the milk, but it is possible that in such cases the fungi or bacteria responsi- ble for the change in the feed pass directly from the feed to the milk after it is drawn from the udder and bring about decomposition changes. The use of distillery waste or slop and of wet brewers’ grains is prohibited by law in some sections. ‘These substances when fed fresh in moderate quantity have no injurious effect upon the milk, but when they are fed in an advanced stage of fermentation or putrefaction the milk may cause diges- tive disturbances, especially in babies, and the manure of the cows has a bad odor and is very soft. In addi- tion, when these substances are fed it is difficult to keep the stable clean and free from bad odors, especially the mangers and storage bins or pits. Particles of the feed remain in corners and crevices and decompose, produc- ing a foul odor. On the other hand, dried distillers’ grains and dried brewers’ grains are entirely wholesome feeds. It is advisable to water the cows at least twice daily. Whether the water is given before or after feeding is of no consequence, but it is important that a sufficient quantity be given. The greater the milk production, the more water required. 12 178 PRINCIPLES AND PRACTICE OF MILK HYGIENE 5. Bedding.—Bedding or litter assists in keeping the cow clean and affords some protection against a hard, cold floor; it also assists in keeping floors clean and dry, especially those of wood and earth, by absorbing the liquid manure. Actual test has shown that when beef cattle are well-bedded they lie down more frequently and for longer periods and make a greater gain in weight in proportion to the feed consumed than they do under less comfortable conditions, and it is reasonable to assume that dairy cows are aifected in a similar manner. The materials usually used for bedding are wheat straw, shredded corn fodder, shavings, and sawdust. From a hygienic standpoint, shavings and sawdust are the most satisfactory. They keep the cows cleaner and are less dusty than shredded corn fodder or straw, but they decay more slowly and are not as satisfactory in supplying humus to the soil. Shredded corn fodder and straw are about equally dusty, but the cows can be kept cleaner with the former. Cut straw is less satisfactory than uncut. Shredded corn fodder excells all of the others in absorbing liquids, with shavings next in order, then straw, and finally sawdust. The low absorption power of sawdust is due to the fact that it is usually damp from exposure to rain. Sawdust is the cheapest material for bedding in localities where it is available. Where there is a convenient market for corn fodder and straw, or where the fodder can be used for feed, it will pay to buy shavings for bedding. All bedding material, except sawdust when it is damp, being more or less dusty, should be put down in the stable after the milking has been completed. This is especially necessary when corn fodder or straw is used, as the dust in these is likely to contain large numbers DAIRY INSPECTION 179 of peptonizing bacteria. Mouldy or musty straw is ob- jectionable because it contains bacteria and fungi which affect the keeping qualities and wholesomeness of the milk. The time required to perform the various stable prac- tices described in the preceding pages is of importance to the milk producer, and the inspector should there- fore be familiar with this side of the subject. The fol- lowing figures were obtained from the manager of a large and successful dairy farm and represent the aver- age time required by different men to perform each operation, the men being timed without their knowl- edge: Taking up manure, 14 minute for each cow 4 times daily. Sweeping platforms, stable floor, and feed troughs, and wiping stanchions, 112 minutes for each cow twice daily. Grooming, 21% minutes for each cow twice daily. Washing flanks and tails, 24 minute for each cow twice daily. Washing udders, two waters, #4 minute for each cow twice daily. Drying udders and drawing fore-milk, 34 minute for each cow twice daily. Bedding, %4 minute for each cow twice daily. Feeding, 11% minutes each cow twice daily. Total time per cow, about 842 minutes twice daily. IV. MILK HOUSE On every farm where milk is produced there should be a special room or compartment to which the milk can be removed immediately after it is drawn from the cow and where it can be subjected to some method of 180 PRINCIPLES AND PRACTICE OF MILK HYGIENE cooling. When the milk from the individual cows is emptied into a shipping can in the stable, it is exposed to contamination by any dust or odors which may be present in the stable air, and, furthermore, it is not likely to be promptly cooled. A milk room is therefore a neces- sity. On dairy farms it has been found to be convenient as well as economical to have this room in the same build- ing with other rooms in which the utensils and vessels can be washed and in which the milk can be stored. A building of this kind is called a milk house or dairy build- ing and sometimes also contains a room in which the milk is bottled. A spring house may, when the condi- tions are suitable, serve as a substitute for a storage room or refrigerator, but the practice of washing the milk ves- sels in the kitchen of the dairyman’s residence is very objectionable. 'The milk house should be arranged so that it will not be necessary for the milkers to enter the room in which the cooler is located or to pass through the wash room to empty their milk pails. This will greatly reduce the labor of keeping the several rooms clean. The floor plan of a milk house in which this idea is carried out is shown in Fig. 17. The milkers pass from the stable to the weigh room, where the milk, after being weighed, is emptied into a tank, from which it is carried by a short pipe passing through the wall to the reservoir on top of the milk cooler. The inspector should observe the location of the milk room or milk house and the materials of which it is con- structed; note the provisions for cooling the milk; exam- ine the condition of the apparatus and utensils and the facilities for washing and cleaning them, and investigate the source of the water used for the latter purpose. 1. Location.—The milk house should be isolated from DAIRY INSPECTION 181 driveways, in so far as this is possible, and there should be an open-air space between it and the stable. If the milk room is not entirely separated from the stable, the chief object of having it, namely, to protect the milk from the stable air, will be defeated. If the surrounding grounds are dusty or if much-used dirt roads are close to it, the atmosphere in the building will be dusty. Some z g g 3 Q Fia.” 17.—Floor plan of a conveniently arranged milk house. A, receiving funnel; B, milk cooler; C, bottle filler; D, refrigerator; E, cooling tank; F, sterilizer; G, Babcock tester; H, bottle washer; I, concrete sink; J, boiler; K, chimney; L, floor drains; M, sunning rack; N, separator. (Hoard’s Dairyman). system of drainage is necessary to carry off waste water and washings, otherwise the air may become foul from decomposing milk. 2. Construction.—On entering the milk house, the inspector should first note the odor of the air. A sour or putrid odor indicates uncleanliness or defective drains. A musty or mouldy odor results from lack of ventilation. The floor, walls, and ceiling should be examined, the material of which they are constructed and their condi- 182 PRINCIPLES AND PRACTICE OF MILK HYGIENE tion in regard to cleanliness being noted. Cement is the best material because it can be most readily cleaned, but smooth boards with tight joints, oiled or painted, will do fairly well for the walls and ceiling, although it is desirable to have the walls finished in cement for about four feet above the floor, especially in the room used for washing the milk vessels and utensils. The floor should always be constructed of cement. The lighting should also be observed. ‘There should be a sufficient number of windows to furnish good light, and some good method of artificial lighting is also desirable. All win- dows and doors should be screened against flies. 3. Apparatus.—The apparatus present in the milk house and its condition should be observed. There ought to be some means of cooling the milk and keeping it cool, and there should be facilities for cleaning the milk vessels and utensils, including a convenient and plenti- ful supply of hot and cold water. If the milk is bottled, a bottle washer, bottle filler, and bottle capper should be provided. These need not necessarily be expensive. A sterilizer is also desirable. It is a protection against the contamination of the milk through returned bottles and it is also a great aid in keeping the milk vessels and utensils clean. A bottle filler and capper will guard the milk against contamination by the fingers. A. cooler, sometimes called an aérator, is necessary for the rapid cooling of milk. This apparatus is con- structed so that the milk flows in a thin layer over a sheet of tinned metal while cold water or brine flows on the other side of the metallic sheet and absorbs heat from the milk. There are four types of milk coolers: (a) conical, ( b) corrugated, (c) tubular, and (d) inter- nal or double-tube. DAIRY INSPECTION 183 (a) The conical cooler (Fig. 18) is a cone-shaped tank with a gutter around the base and a movable reser- voir at the top. The reservoir has small perforations in the bottom around the periphery. When the cooler is in use, the cavity of the tank is filled with water or ice water. The milk is poured into the reservoir and, passing out through the perforations, flows in a thin layer down over the external surface of the conical tank, col- lecting in the gutter at the bottom. From the gutter it is permitted to run into the shipping can or bottler. aoe--- AGITATOR “VENTILATING TUBE ~-- PERFORATIONS \---OVERFLOW PIPE \ FOR WATER Fia. 18.—Cooler of conical type. One model of this type of cooler has attachments for pipe or hose to carry cold water into the tank and to remove the water which has been warmed by the heat absorbed from the milk; another which is intended for use on farms without a water pipe system does not have these attachments, and the warm water must be removed and the cold water added with a dipper or similar vessel. (b) The corrugated type (Fig. 19) of cooler consists of two sheets of corrugated copper, with a small water- tight space between them and tinned on the outer sur- face. The cooling fluid enters through a pipe at the 184 PRINCIPLES AND PRACTICE OF MILK HYGIENE lower part of this space and discharges at the top. The milk is poured into a reservoir or tank at the top of the corrugated metallic sheets and, passing out through perforations in the bottom of the reservoir, flows slowly downward in a thin layer over the corrugated surfaces to a trough at the bottom, from which it passes into the Fic. 19.—Corrugated type of cooler. collecting can or bottling apparatus. A late model of the corrugated type of cooler is conical in form and is provided with a metal cover to protect the milk from contamination while it is passing over the cooling sur- face. (c) The tubular cooler (Fig. 20) consists of a num- ber of pipes arranged horizontally, one under the other DAIRY INSPECTION 185 and close together. They are connected at either end so that fluid can flow from one tube into another. The cooling fluid enters the bottom pipe and flows upward through the various pipes, while the milk flows down- ward over the outer surface of the pipes from a reservoir eH ) A ty = eH ws 7) og On THEN 2 Bok Yes Piss a Fia. 20.—Tubular cooler, with continuous surface. at the top and is received in a collecting tank at the bottom. In some coolers of this type the pipes can be taken out to be cleaned and sterilized. Sometimes these coolers are arranged for ice water to run through the lower pipes and water through the upper pipes, the object being to save ice. The corrugated coolers have an ice-water section which can be attached to the bottom. 186 PRINCIPLES AND PRACTICE OF MILK HYGIENE (d) The internal or double-tube cooler (Fig. 21) is a system of double pipes, one within the other. The milk flows through the inner pipes and the cooling fluid through the outer. In this type of cooler the milk is protected from possible contamination from the air. To facilitate cleaning, the connections between the individual pipes are removable (detachable return bends). With a cooler, the temperature of milk can be low- ered to within a few degrees of the cooling fluid in a few minutes, provided the apparatus is not pushed be- yond its capacity. If the cooler is not large enough, the milk is likely to be permitted to flow over the cooling surface too rapidly for much of the heat to be absorbed by the cooling fluid. The size of the cooler required will depend on the quantity of milk to be cooled and the number of milkers. The capacity of coolers as stated by manufacturers is usually based on 20 square feet of cooling surface per 1000 pounds of milk. Milk should be cooled to as low a temperature as possible, and should be kept cool. 'The lower the tem- perature, the slower the bacterial growth and the longer the milk will keep in good condition (see page 43). Above 60° F. the bacteria multiply rapidly, and at 70° F. or above growth is not only very rapid, but the de- velopment of the more objectionable bacteria is favored. When well water or spring water is used for the cooling fluid, the temperature of the milk cannot be reduced much below 60° F. and often not that low. ‘The tem- perature of well and spring water in the section around Philadelphia ranges from 52 to 55° F. in the spring and summer months, but in the late summer and early fall it is usually higher, especially in sandy regions, rising to 69 and 70° F. in some sections. With ice water, the Fig. 21.—Internal or double-tube cooler. DAIRY INSPECTION 187 milk can be cooled down to 40° F., while with ammonia or brine it can be brought still lower, even to freezing.’ The cooler must be thoroughly cleaned each time it is used, stored in a clean place, and protected from dust while in operation, or the milk will take up large num- bers of bacteria during the process of cooling. When the cooler is not properly used and cared for, it has been found that better results can be obtained by pouring the milk directly into a shipping can and placing the can in cold water, although the temperature is lowered very slowly under these conditions, three to four hours being required for the temperature to fall to 60° F. In some cases it has been found more satisfactory to have the milk taken in cans to the shipping station and to cool it there. When this plan is followed the milk must reach the shipping station during the period the germi- 1 In the northern part of the United States, about 114 tons of ice will be required each year to cool the milk obtained from each cow, while in the southern states about 2 tons will be necessary, allowing for the waste by melting. A ton of packed ice will occupy 40 to 50 cubic feet of space; 12 inches should be allowed on the sides and bottom for sawdust or other pack- ing material and 8 to 4 feet on top for packing and ventilation. With these figures, the dimensions of an ice house of any ca- pacity desired can be determined. ?" lAsnetur neck and the bottle is replaced in the centrifuge and whirled for two minutes. Hot water is again added until the fluid in the bottle is raised to a point near the top of the graduated scale, the water being dropped directly into the fluid, not run down the side, in order to remove any flocculent material which may be entangled in the fat at the top. The bottle is then whirled another min- ute. After the whirling is completed, the fat should be collected at the top of the fluid in the bottle in a column of clear, yellowish liquid, with a nearly colorless fluid below it. The fat column should have a well-defined 236 PRINCIPLES AND PRACTICE OF MILK HYGIENE meniscus at the top and bottom, and the reading should be made from the bottom of the lower meniscus to the top of the upper one. A pair of calipers will be found convenient for measuring the fat column. The tem- perature of the contents of the bottle should be between 130° and 140° #. (54° to 60° C.) when the reading is taken. Foam on the top of the fat column is caused by using hard water. Dark colored particles in the fat column may be due to several causes: acid too concen- trated, too much acid, milk too warm when acid was added, allowing acid to mix with milk when placing it in the bottle, allowing the bottle to stand too long before mixing the acid and milk, and interrupting the mixing before the solution was complete. White particles in the fat column may result from acid which is too weak, too little acid, acid or milk being too cold, and insuffi- cient mixing. Immediately after the reading is taken the bottle should be emptied, rinsed out twice with boil- ing water and placed in a rack to drain. Now and then the bottles should be washed in a solution of soap powder or in a dilute solution of lye. The Babcock test for fat in cream is made in very much the same manner as for milk, except that a bottle with a longer neck and more extensive graduations is used and the cream is weighed instead of measured. There are two sizes of bottles, one for 9 grammes and the other for 18 grammes of cream. The test bottle is placed on the scales and the cream is introduced into the bottle with a pipette. Sufficient sulphuric acid is added to give the mixture the color of coffee; the quantity required will vary with the per cent. of fat in the cream. The bottle is then whirled in the centrifuge and water added exactly as in testing milk. On being finally re- METHODS OF EXAMINING MILK 237 moved from the centrifuge, the bottle is placed in water at a temperature of 135° to 140° F. (57° to 60° C.) and submerged to a point above the fat column for 15 minutes, after which the per cent. of fat is read off from the scale. The reading is taken from the bottom of the lower meniscus to the bottom of the upper one. It is recommended that the upper meniscus be destroyed by dropping a few drops of glymol (liquid petrolatum, white min- eral oil) into the test bottle and the reading taken from the bot- tom of the lower meniscus to the line between the glymol and the fat. Gerber Test.—(Fig. 36.) This test is used almost exclu- sively in Europe and to some ex- tent in this country. The prin- ciple is the same as in the Bab- cock test, except that the fat is not only liberated from its emul- sion by sulphuric acid but is also dissolved in amyl alcohol. The apparatus required con- u it Fig. 36.—Bottle and pipettes used in sists of a special type of bottle Gerber test. (G) known as an acido-butyrometer, which has a long neck containing a scale graduated in tenths, each division representing 0.1 per cent. of fat, and an opening in the bottom which may be closed with a rubber stopper; also three pipettes: 1 of 11 ¢.c. capacity to measure the milk (K), an acid pipette holding 10 cc. (H), and a 1 c.c. pipette for the amyl alcohol (I). The chemicals used are commercial sulphuric acid of a specific gravity of 238 PRINCIPLES AND PRACTICE OF MILK HYGIENE 1.825 at 15° C. and amyl alcohol. The test is made as follows: The milk and the chemicals should be at a tem- perature of 15° C.; 10 c.c. of sulphuric acid are measured with the acid pipette and placed in the bottle. The point of the pipette should be passed obliquely through the opening of the bottle until it comes in contact with the side of the bottle, when the acid is allowed to flow slowly out. Care should be taken that no acid is deposited in the spiral grooves on the inner side of the opening. After thoroughly mixing the milk, 11 ¢c.c. are drawn up into the proper pipette and placed in the bottle with the same precautions, the milk being permitted to flow slowly down the side of the bottle so that it will not mix with the acid. Then 1 c.c. of amyl alcohol is placed in the bottle in the same manner with the alcohol pipette. The three fluids should be arranged in three distinct layers. The bottle is closed with the rubber stopper and the fluids are mixed by slowly raising first one end of the bottle and then the other, permitting the fluid to flow in and out of the neck. This is continued until a perfect solution is obtained. 'The rubber stopper should be forced in sufficiently to raise the fluid to the zero mark on the scale in the neck and it should be held in place with the thumb while the bottle is being shaken. This latter precaution is taken to prevent the stopper from coming out, although this is not likely to occur if it is properly inserted. The bottle should be placed in a water bath at a temperature of 60° to 65° C. (140° to 150° F.), with the stopper downward and the water covering the entire bottle, until it is centrifugalized. 'This will not be necessary, however, when only one or two samples are being tested. If a hand centrifuge is used the whirling must be continued 10 minutes, but with a METHODS OF EXAMINING MILK 239 power machine making 800 to 1000 revolutions per min- ute 3 to 4 minutes is sufficient. When the bottles are removed from the centrifuge they should be submerged in an upright position, with the stopper downward, in a water bath at 60° C. (140 © F.) until the reading is taken, unless the samples are so few that il os can all be read in a few seconds. The fat collects in > a clear, yellow column at the top of the fluid in the neck. The stopper is turned sufficiently to bring the lower border of the fat column on a level with one of the main divisions of the scale and the per cent. of fat is then read off. The read- ing is taken from the bottom of the fat column to the lower border of the menis- cus at the top. After the reading is taken the bottle should be emptied at once and cleaned as directed for the Babcock bottle. A. special bottle is made for testing cream. The cream placed in the bottle is weighed; otherwise the per cent. of fat in cream is determined in the same manner as that in milk. Lactoscope Test.——It was proposed some time ago to determine the per cent. ne . : : Fia. 37.—Feser’s of fat in milk by measuring its transpar- _lactoscope. ency. Several forms of apparatus have been devised for this purpose, the simplest being Feser’s lactoscope (Fig. 37). This is a glass tube, contracted towards the bot- tom. % 100 p represents per cent. of fat in total solids, f per cent. of fat in the milk and t per cent. of total solids. The per cent. of fat in the total solids varies from 20 to 34. It is decreased by skimming. DETERMINATION OF THE DEGREE OF ADULTERATION When it is possible to compare a sample of adulter- ated milk with a sample of the same milk collected under conditions which exclude the possibility of adulteration, the extent of the adulteration may be determined approxi- mately by the following formulas of Bohmlander: m==x w —W fR METHODS OF EXAMINING MILK 247 In the first formula W is the per cent. of water in the unadulterated sample; w is the per cent. of water in the adulterated sample; R is the per cent. of solids not fat in the unadulterated sample; r is the per cent. of solids not fat in the adulterated sample; M represents the quantity of water to 100 grammes of milk. In the second formula F is the per cent. of fat in the unadulterated sample; f is the per cent. of fat in the adulterated sample; R is the per cent. of solids not fat in the unadulterated sample; r is the per cent. of solids not fat in the adulterated sample, and E represents the per cent. of fat removed by skimming. TESTS FOR NITRATES AND NITRITES Soxhlet’s Test—One-half c.c. of a 20 per cent. cal- cium chloride solution is mixed with about 30 c.c. of milk and the mixture is boiled and filtered. A 2 per cent. solution of diphenylamin in chemically pure sulphuric acid is added in sufficient quantity to some of the filtrate to make it milky. Chemically pure sulphuric acid is then poured slowly down the side of the test tube so that it forms a layer at the bottom. If nitrates or nitrites are present a blue zone is formed at the point where the two fluids come in contact. 'This test will detect one part of ‘nitrates in 100,000; most farm water contains one part in 10,000 (Jensen). A modification of this test is described by Rievel as follows: Place a small quantity of milk in a test tube and then pour in slowly, so that the two fluids will not mix, a solution of diphenylamin in chemically pure sulphuric acid (1:10). If minute traces of nitrites are present a blue ring will form at the point of contact of the two fluids. 248 PRINCIPLES AND PRACTICE OF MILK HYGIENE Fritzmann’s Method.—Place 2 c.c. of milk in a test tube and slowly run down the side 2 cc. of pure sul- phuric acid to which one drop of a dilute formalin solu- tion has been added. In the presence of nitrites a blue- violet ring will form at the point of contact of the two fluids, but the reaction will not occur in the presence of albumen. According to Riegel a suitable formalin solu- tion may be made by adding one drop of 40 per cent. formalin to 300 c.c. of distilled water and mixing 15 grammes of this solution with one litre of concentrated sulphuric acid. This method gives very accurate results and is easily carried out (Rievel). Fresh, clean milk does not contain nitrites.