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.
PRINCIPLES AND PRACTICE OF MILK HYGIENE
24
siete O38 | O'OT | 08's 983 | O8'L FHS [| Orgy Pe") oes ( OST | 98°6 { 98'S | OS'S | SLIT Se SU UREN
sevens] setesteeeees[eecrefenectens|enenee! (Qh (1) (s1) rettsetelesecss[ereceseetonereet egg fereered gog [rere l gary [occ e ttt HOR MON
"TTT OBL || OFT | O84 $96 | OFLE9 | OBS || OOFe | °"' "| OO'OT | S'S8 | OBI | 9S | Gas | OFS | ELIT | epeaany
Sanndd |sdotenllasoqud| pects Surge |sareee lesen ec | terse el sate eeens | ceramics |seearn |e asec c} cues) aneenn|@ontae| smsiue lilies: [is susie c sso OO TUMON
968 | O'OL | $5'°6 | 00'S || OTT |. Sesr0p Many
meme cep meee a Pewee ee le reer ela wee ernn ts cenesl[o serves sceesnslovnevccens . rs er ed
a OFT Zs OFT () (,) Q) (1) Therelsretenelsiors () eoceee 00°91 0°08 O'sI 09°8 wevceepectces 00°81 ‘cots aanysdue yy MON
eel op [tec] gen [cee cf ocees[reemeees fectee fee eseeeneefecetiees |e cree] area eee | ORT Tee eee occ cutee ag tniqany
Bere eotete eu cG er ee [Oc ee | ees srccreleoesrel gg-gr | grag | gros |o-''"| gee | ose | gaat [ccc es emeyuope
Ute enol ot | L928» | oss | zoey | orgs joo] orgy [eect | eee | ovat | gee | eas | 908 | ooved [oes coe umosetyy
Pe es es . os i Cs oe er ey Pos Oe es ee es a Oe eC i CO es Ce er ear rer as rr er ar rears wee see seen Titres", td sstssryyy
ost | os | 93 | 008 | 0788 | (a) o'shy |-"''*'| OoTOT |°°"""| O08 |°"'**"] 98's | S2°6 | OO'ST [°° 777+ eqOsauUTAY
OOL (2) @) (,) (2) (or) 00S ’ a ed CACO POT 5 0°08 Osl see eee 00°S eee eee OF SL CC eek pt ek CE “UBsIyolyy
Oe fol] Gy | Gd lect reel csees{ seresoelernesl oer | opal gore bce lenter |: 2-2) eeenqauann
op focus ogy) [ggg frp b ete ceed oer | ee | ose [coc foeed [ioc pusparapy
Orie eperess [vate "on ee corgs ones fcec[eceee|eere| ost [n't gee | one [gurt octets semneee
ot | oor} () (2) (1) (1) (4) @ | @ () | (| 00'8 | og's | oss [o7""* "7" BUBISINOT
pees O'FL | 99°28» | 0°83 | 99°48» | 0°83 = ae 98°6 | 98'S | O98 || Ayonquey
seveslaqiey eerste lon elec eae : TOOL Ogg [ettees|eceres [eeeeeeeeee ose pupmBSE
‘OL (,) (,) (1) (1) (11) ‘BOP, e 6 6.6.8-))050:0.010:6) 1. ne: e 1,8 )0lare . ~ ee 00'S Chey a A 00°s1 eee eee LNT §
aealeaae=legesel age oeletege | onese gpa lieve ogg eunipey
i o8'6 | 00'S | 098 [| siouny
3
3
=
a
=
e
=
=
cos
2
°o
®
7
oe
—]
©
~
ra pat et
=
o
aa
~
=
i)
19
~=7
I () () 09°23» 0°83 os'6 | oss | 008 | ov It | oo oqepy
tele cess cents sets eloventacelons Ce Pee ine Ieee Gears Srer errr Seneoo| Tye jlo OonD o¢'IT SE TT
5 2 ces | oss |: soloists GIBIOSE)
o3's | ogg [tt series acs Pole ep urd
OS'S | 00°6 | OF'ST || Brquinyor Jo oNIsI
EGS Os |RDINEEO) SOR | DOOD ODOUGO ISS RT INC CY at
oes 098 On iy | 0000 qmanaeud05
renee |oceeea|eceeererees ess OnBI0I0r
S itn DOMeMDAor ada
x)
I () (,) (1) ()
| oz oes | ond ORS [oo eetetree[ecettees|ecceee|ecnerens
=| (6) | (8) ORS OP 0) (s) | 00°2 | 00st
Sipond shouno| ououn|loanoce (s) (s) | cots» | 08%
See |e O10 Loe | 20-1 (9) (0) | OLL 0°88
90 | 08 90 | OOL | 08's O98 | OL'L OFS
=~
cS
LYS
=
~
~
ogg foo feet eee enmopyeg
“'o) sesueHIy
ber eeseseeeee gmoginy
Dees eeeeeee ee eaeery
eer “+; emeqety
se eees eevee ees te nveee Ce ra eeceee seo eee
eeeneele see
eps cecee Ce ee ee ee ee ee ee ee eeee
Sere fe eels ce fie sete fv eee els cece mele ace eels scccnse feos eeefeaneseccet ls coscccelocuverfacvvecsete
*9 40 \"49 49g \"70 42q)"19 40g) 10 bod? |"}9 40g) "70 49g |"9 dag) "79 dag | ‘40 dag” |"49 dag} *49 Sag |*40 4ag|'30 sag’|"30 sag'|"79 saq’|"49 49q1|"79 4aq.
ary uy
py | Md | epg) ME) Wad SPHO| ae | SPMOE
sprjos (223200) sprfos
OL Pere = = eae ee rica | Ppt eon,
(qnu (pedezeoas (pamejeaas) o600q49 ase0q9
es ae Bivelg722 pai AT porepaoD Beaune Sarl a 9) mrs :
897836
‘SLOAGOug ALYIVY] HOA SAUVGNVLG IVOF]
MILK
“HIM poropatod 10] sprepuyys oad sz10da1 ON
"AIOPLI9} $9397 poy Ul epwuT saz]Nq [Te 0} saldde siqy,
“OT WBG7 SS9'T og
“peMolle OU 9] ueq} sso]
‘OS UBY} S597 og
‘OE BBY] S50] og
*g Uey}
S89] “MITA “g ‘Wlvaro YZINOJ-aUO fg] ‘UIvaIO JpeYy-aUO ‘Eg ‘uIvAIO 5}.MOj-9014,[, 9g
“UALS J[BY “OF OF GT SUIys SYZIN0j-9a147 “GT 07 O° SULTS “C"y, UBT} SST cg
*Y8} aq OF Y}ANOJ-9UO HLT opNio UI spTOS Jo *yuao Jod zT 07 puodsai100 ysn Py zz
‘1S ‘prepurig ‘og ‘Meal Ia iz
“UIBIID VOI Ulead paljaqvy ji suoT[es QT ur seouno OMT, oz
“y8¥ eq OF YIIMOJ-au0 Sy[lor apnso UI splos *yuao sad g*]{ 0} puodsass09 ISNA ox
“WIpys [eloads ‘avo JO gy ‘umTyS UINIpe “gy 07 §[ ‘WIys payieu gy] ueyy 859] gt
“9% MOTE TV ar
‘OS Wey} ssa] AUY 9,
“HIM 10j spsepuezs 0}0}8 0) UORN[P payezs Uo puodsass09 ysnyY gy
‘V8J UE SPLOS or
“paulezaleur SI 4ej FI yUNOUTY AUY gy
“prepueys on 4nq ‘pouyeg gy
*pepuwiq Os eq 4SNJl 1
*PaMOT[® ION or
“PPTPAE] 24 PIMOS 6
*VIGUIN OL) JO JOUASICY aq) 09 sattdde gogT Jo 0" Snip pure poo} s93%}g paymy g
“Pawpurys 693876 pozay) ,
*‘Pesmepuod 8 passe] g
“PAT 42] 24 ISNA 2
“spljos [8}0} UO paseq 4B} Jo aduzUIOIIg »
‘ayes Jo saoeid [je ut paceldsmp st P48] adie] JT
pasn aq Avur caead9 ao! UI siO][IY ‘syONposd pooy [[e 10J sprepueys [eIapay ¢
*SPivpueys [ELWOPII0} ON g
ee
Srp he lester Ose [eS An | 186! | 09°28» | 0188. | tae ss| 0:00!
Bent |e ears | OsVE | 00'S 5) 0188) | 0078 | O;se een aes O0gi9)
Aaseama| sane maa (s2) 008
(x) | 08 0°83 Tree | ORD
eT Oey | SS : ‘| g-09,
(2) (1) (1) 0°08
eed org | () ; |G)
seoeeel guy | 0°98 ; 1 900»
aera KASS eae 0°86 iM ten peed ZOOS 9e
ot fos for. 098, sees] ogy,
seseeed Qegg [eeeees 0°98 f “+1 9:09,
o9 | 9 (:) 0'ss
Hp On Ok NSiee) bed | O08 ee
. ee eee ener eee eee ee eee ones (rz)
OSL | (oz) | OFT 7?) (:) peaclccie eee laee(()
“spivpueys 97816 ON x
‘"''""| 00'9T uz) 9°88 | OST | 98°6 | So's | Oss [°° 827845 pazag
. Cs oC er ie COs Oe Oe OC ee aC ee ar Ge a ery srtesssesss*) SUTMOL AA
“olsosse] gee | ot | go's | oors | 09's [cere {eee cece fatemopeite
nee seeeereeto covet arsccetsseecetoecoesefeacsceeles vlvcece Trees ss) BTTIBITA 9894
vret|eseeeeeeteseeee! gear | ogg | eae | ozig teeeee sess ‘aoa gangs ay
"| 00'9E | 9°28 | O'st | 98°6 | 93's | 09's oe Se eTU ITA
sacote|[aneanenal| as IE ary || paral rears | eee vse eeeeereseeeqpumEsy
pan mime Ihe Lae eee eae | oe oeeeseeeeeneureraaa yt
soos lctatoonll car tase ll cre || ceases vee t eee ceeeeeen gaat
wal earetel eras Conia acculinas nenoonacmcorns pce
enna paoanecall as eaeclcoae “3 >=" momuEy danod
Fie badtoccce oe aes stete|ortete[ooses [ooeoeser gmoney WanoS
aoe og's |:<°**"| oo'st |:¢2+-7* puepse epogie
ae setseelecseeelonnete[ecsees[onnons [ooeeeee os Pgh EOD TH.
a O'sI | 93°6 | 98's | 09°8 | S411 |" *** spurysy ourddyyg
() Ost (1) 93'S sere ee 00°S1 wee oe BruealAcuueg
er eee OST ween 06'S 038 OL'IL ee ? *“M032IQ)
ae writteleecess[amnees[ennets[antin [eossseeeee rg SmORBEIO
eee verereleereed gpg [overs gggt feereete erie ss stone
()) o'st wees 00's see 00°31 srorresss*soNBC WWION
26 PRINCIPLES AND PRACTICE OF MILK HYGIENE
The standard of the United States Department of
Agriculture calls for 3.25 per cent. of fat and 8.5 per
cent. solids not fat for milk; 9.25 per cent. solids for skim
milk, and 18 per cent. fat for cream. 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.