up the heat of the body, therefore it is a matter of practical economy to keep cattle warm in the winter. Similarly, the yield of milk becomes less in quantity and poorer in quality, if cows are allowed in the summer to be teased by dogs or flies, or in anyway compelled to take much exercise.

Struckmann made some very valuable experiments in 1859 upon cows of good breed, "superior," and cows of an "inferior " breed. The method of feeding and the results are tabulated in annexed table (XVII).

The conclusions drawn are

(1.) That most milk is produced by a diet of 5.4 lbs. rape cake, 36 lbs. mangolds, and 25 lbs. oat-straw.

(2.) That a reduction of 9-10ths lb. of rape-cake diminished the milk of the superior cows, the eight cows in the 3rd period yielding about a gallon less milk daily; hence, 1 lb. of oil-cake produced 1.2 lbs. of milk.

(3.) In the sixth series, the cows received 6 lbs. less brewers' grains, which diminished the produce to the extent of about 1-10th of a gallon; thus, 1 lb. of brewers' grains produced about a quarter of a pound of milk.

(4.) In the first and third series, very nearly equal quantities of milk were produced. In both sets the same quantity of mangoldwurzel and oat-straw were given; 18 lbs. of brewers' grains of the first series were replaced in the third by 45 lbs. rape-cake; hence, 1 lb. of rape-cake equals 4 lbs. of grains in milk-producing power. The authors noted that rape-cake produced milk richer in butter than that obtained from cows fed on brewers' grains; but the butter in the last case had a better flavour. It is curious to note that the superior breed was more affected by change in diet than the inferior :-In the first period, the four superior cows gained 100 lbs. in weight, and yielded 343 gallons of milk; the four inferior gained 304 lbs. and yielded 227-2 gallons of milk; or, to put it in another form, in thirty-six days the superior cows produced 115-8 gallons more milk, and gained 204 lbs. less live weight than the inferior; from this it would appear, that 51 lbs. of milk were replaced by 1 lb. of flesh.

§ 168. The colouring and the alkaloidal and active principles of plants impart their distinctive properties somewhat readily to milk. Thus it has long been noticed that browsing on certain plants affects the colour of milk: Caltha palustris, saffron, and rhubarb colour it yellow; rhubarb, opuntia, and Rubia tinctorium, red; Myosotis palustris, polygonum, and Anchusa equisetum, blue. Purgative vegetables, such as rhubarb, or even the juices of acid fruits, taken by a suckling woman almost invariably affect the infant. There are instances of milk becoming

poisonous from containing the active principles of plants. In June, 1875, an epidemic of diarrhoea occurred in the Rhone Gorge, and was traced to goats' milk, the goats having browsed in fields where the meadow saffron was growing. Professor Ralti isolated colchicine from the milk. Similar outbreaks, caused by the animals having fed on poisonous shrubs, have been recorded in the Western States of America and Australia. There is a supposition that the exposure of a cow to bad odours, or to putrid emanations, has an influence on the milk. Mr. Willard cites instances of cows yielding milk quite unfit for making cheese, in consequence of the animals having inhaled the putrid emanations of a dead and decomposing cow. Mr. A. H. Smee* has also stated that the milk of cows fed on sewage farms rapidly putrefies, but no details as to the manner in which the samples were collected are given, and the explanation may be that the putridity of the milk was not due to the grass eaten, but that the teats of the cow were fouled by decomposing substances, which would mix with the milk and infect it. A most notable example of this is related by X. A. Willard.‡

In a large American cheese-factory much trouble was caused by decomposition of the milk. The cause of this was traced to one farm, and it was ultimately satisfactorily demonstrated that the animals every day walked through a putrid slough, the matter adhered to the teats, there dried, and particles fell into the milk, with the usual result, so that the possible want of cleanliness in some of the details of milking must always be borne in mind in such inquiries, and especially the probable presence of bacteria on the external skin of a cow exposed to putrid emanations. The subject is of great importance, and needs further inquiry. In any future experiments as to the influences of grass manured with sewage on cows' milk, the teats and udder should be washed with a solution of some disinfectant before commencing the milking, and more than ordinary care should be taken that the receptacles are in a cleanly state.

§ 169. Experiments have been made with the object of ascertaining whether metallic compounds would be excreted by milk. Arsenic passes readily enough in minute quantities, and the same may be said of lead and oxide of zinc. Antimony also, if administered, appears in the milk. The statements with regard to mercury are conflicting, but the balance of evidence leads, on the whole, to the conclusion that it is not excreted, even in minute quantities, by the mammary glands. Bismuth, Milk in Health and Disease," by A. H. Smee. London, 1875. +"American Milk Factories," by X. A. Willard, A. M., of Herkemer, New York. Journ. Agric. Soc., viii. 1872.

when administered, was detected in milk by Marchand, Lewald, Chevallier, and Henry. Lewald gave 15 grms. of potassium iodide to a cow, and its presence for four days afterwards was detected in the milk; 21 grms. were then given, and the drug could be detected so long as seventy-two hours afterwards. On administering it again, it was found in the milk for eleven days.

THE QUANTITY OF MILK GIVEN BY THE COW,
THE METHOD OF FEEDING, &c.

§ 170. The capacity for milk of the udder of the cow is usually estimated at about 3 litres [66 of a gallon, or a little more than 5 pints]. The quantity of milk secreted is about three times this amount, but varying in individual cows, and depending on circumstances, such as the breed, the health, the size of the cow, the time after parturition, and the nature and quantity of the food given.

In

§ 171. The breeds in England most approved of are the Alderney, Ayrshire, Holderness, Kerry, and Suffolk. Germany, the Swiss, Allgäuer, and Dutch cows appear to be the favourites. Some careful estimates of the amount yielded by different breeds of Continental cows have recently been published as follows:

TABLE XVIII.-AVERAGE YIELD OF MILK.*

own. The

These breeds, then, are not superior to our favourite cow of the London dairymen appears to be the Yorkshire cow, essentially a shorthorn. The average yearly yield is from 600 to 700 gals., 15 of these cows giving about 10,000 gals. of milk yearly, or 17 gal. per day; individual cows, of course, occasionally exceed this. A cow has been known to give daily for some time as much as 5 gals. of milk.

To

The time elapsing before and after calving causes, as might be expected, considerable variation in the mammary secretion, the quantity augmenting during the first two or three weeks, and diminishing towards the end of the third or fourth month. wards the seventh month the quantity sinks to one-half, and in the ninth and tenth months it is often reduced to three-quarters of the quantity secreted at first. On the approach of calving, the milk ceases altogether.

The age of the animal has some influence, very young cows secreting less than mature adult cows. It is also found that, cæteris paribus, the larger the cow the greater the yield of milk. Mr. Ockle of Frankenfeld took four Dutch milking cows, two weighed 2112 lbs., and two others only 1537 lbs.; he fed them on the same food, and submitted them to similar conditions for sixteen days. The results of this experiment are embodied in the following table*:

§ 172. The feeding of milking-cows varies somewhat according to local circumstances. In town dairies brewers' grains are much in use, and one to two bushels are given daily, besides mangolds, hay, and meal to each cow. A very common course of home-feeding is as follows:+-At 4 a.m. the cow receives two or three pecks of grass, immediately after being milked, then 4 to 5 lbs. of hay; at 9 a.m., from 20 to 25 lbs. of chopped mangolds, and another 3 to 4 lbs. of hay; at 1 p.m. there is a second milking; another similar feed follows, and she is given plenty of water.

* On Milk, by Dr. A. Voelcker, Journ. Agricult. Soc., xxiv., 1863.
†T. Carrington: Journ. Agricult. Soc., xiv., 1878, p. 670.

If

oil-cake is used, 3 to 4 lbs. a day are given either with the mangolds, or in a gruel with the grains. In the country the chief dependence is placed on hay, mangolds, barley-meal and bean or Indian flour; in the summer, abundance of green food is given, such as clover, vetches, cabbage, &c.

CREAM.

§ 173. Milk on being allowed to rest for some time becomes covered with a yellow fatty layer, known as cream. In composition it fairly agrees with ordinary milk, save that it contains a large percentage of fat, and that there is also a somewhat relatively higher percentage of caseine and albumen. The albuminoids have a tendency to separate partially, and mechanically adhere to the fat; for example, the author found the average composition of Devon cream as follows:

It will thus be seen that the milk has thrown up caseine with the fat, for if we allow that ordinary milk contains 86-87 of water and 3.98 per cent. of caseine, then the amount of caseine in the cream, if none were separated, would be

Water. Caseine. Water. Caseine.

86.87 : 3.98 28-675 = 1.31

But the cream, instead of containing 1.31 per cent., actually contains 2.22 in excess of this quantity.

The amount of albumen strictly follows the caseine, for the ratio of caseine to albumen in milk being as 3.88 is to 77, the theoretical yield of albumen in this particular case would be 66, the amount actually found being about 1 per cent. lower than this estimate.