animals were fed on a uniform diet of bran, hay, and oats. The yield of each milking was carefully noted, and the ass in each case milked dry. It would appear that the milk of the ass under these circumstances has a very uniform composition, the differences observed being quite unimportant. The yield for commercial purposes appears not to exceed 3 pints, and to average about 21 pints daily. More than this is doubtless secreted, but some of it is used by the foal. In no case did a single milking yield half a litre (three-fifths of a pint), but usually between 300 and 400 cc.

The mean composition of asses' milk is as follows:

The fat contains 5 per cent. of butyric acid, equal to 6.6 per cent. of butyrin; it is probably very similar to butter-fat. After the precipitation of casein, albumen, lactochrome, and peptones, there yet remain principles precipitable by tannin. As in human milk, the casein is not readily precipitated, but remains suspended in a state of fine division, however far lactic fermentation may have progressed.

§ 126. Milk of the Goat.-The milk of the goat,* as a rule, contains more cream than that of the cow, and rather less albuminous matter.

* Some analyses by Voelcker (Bied. Centr., 1881, 858) of goats' milk give the following results:

§ 127. Milk of the Mare.-The milk of the mare closely resembles in its constituents the milk of the cow: the casein, the sugar, and the fat being very similar, if not identical. M. J. Duval* asserts that he has discovered in the milk of the mare a new acid, to which he has given the name of equinic, and which crystallises in groups of little needles; it is not volatile without decomposition, in odour fragrant. It is combined with a base volatilised by heat, which the author considers a base of the ammonia type. Its reactions with silver nitrate, ferric chloride and auric chloride distinguish it from hippuric acid. No analyses are, however, given.

The mean composition of mare's milk is as follows:

MILK OF OTHER MAMMALS; LACTESCENT PRODUCTS OF BIRDS AND PLANTS.

The following Notes on the Composition of the Milk of other Mammals, &c., may be found useful for comparative purposes.

§ 128. Milk of the Sheep.-Sheeps' milk* is remarkable for its high specific gravity, and the large amount of solid matter which it contains; the specific gravity ranges from 1038 to 1041, and the total solids may rise as high as 19 per cent. The average composition is as follows:

The casein behaves similarly to the casein of cows' milk, and separates easily by dilution, acidulation with acetic acid, &c. (see p. 282). The fat yields 5 per cent. of its weight of butyric acid, and is probably of similar composition to the milk-fat from cows' milk.

$129. The Milk of the Camel.-Chatin has analysed the milk of the camel. He describes it as perfectly white in colour, and possessing globules smaller but more numerous than those in cows' milk, the diameter being on an average one-half. Specific gravity, 1042. It appears to be rather richer in milk sugar and casein than cows' milk. Dragendorff has also analysed camels' milk, and gives the following figures:

§ 130. Milk of the Llama.-Doyéres has analysed the milk of the llama. The mean of his three analyses is as follows:

§ 131. Milk of the Hippopotamus.-There are few opportunities of analysing

An analysis, by Voelcker, of rich samples of ewes' milk shows that the fat may attain 12.78 per cent. Bied. Centr., 1881, 858.

Sur le Lait de la Chamelle à deux Bosses, par M. Chatin. Journal de Pharmacie et Chemie, t. i., 4 ser., p. 264.

Zeit. f. Chemie, 1865, s. 735. § Ann. de l'Inst. Agrom. 1852, p. 251.

the milk of this enormous animal, as it is fierce when it suckles its offspring. A sample of the milk was, however, investigated by Gunning.* He describes it as of an acid reaction, and under the microscope showing larger globules than that of other animals. The young hippopotamus sucks under water, and can remain there for a much longer time than the adult animal. The secretion of milk is excessive in quantity, and escapes from the distended teats in streams, which make the water around the animal quite opaque. Its general composition appears to be as follows:

§132. Milk of the Sow.-The mean of eight analyses collected by König† of sow's milk, is as follows:

There are also two analyses of the milk of a sow investigated by Filhol and Joly; the animal was fed on horse-flesh, a diet far from natural; under this diet was secreted a highly albuminous fluid, containing but little sugar. Specific gravity 1·044.

Per cent. 12.89 21.0

§ 133. Milk of the Bitch.-The milk of the bitch is highly charged with albuminous solids, and is of a specific gravity ranging from 1034 to 1036. It has been investigated by Simon, Dumas, Filhol and Joly, Talmatescheff, Bensch, Scubotin, and others, with the following mean results :

Milk-fat,
Casein,

Albumen,

Milk-sugar,

Ash,

Water,

Total solids,

Solids not fat,

:

Per cent.

9.57

5.53

4:38

3.19

73

76.60

23:40

13.83

§ 134. Milk of the Cat.-The milk of the carnivora generally has the peculiarity of having the milk-sugar almost entirely replaced by lactic acid, and hence the milk invariably possesses an acid reaction. An analysis of the milk of a cat by Commaille is as follows. The milk was taken twenty-four hours after kittening; it was feebly acid :

The 467 would correspond to about 25 of peptone.

§ 135. Milk-like Secretions of Birds and Plants. -It is usually held that mammals alone secrete milk, but this is by no means certain; for during the latter portion of the incubation-period, as well as more profusely for a little while after the young birds are hatched, the pigeon secretes a nutritious albuminous fluid in her crop, which is supposed to be used for the purpose of feeding the young birds. According to Lecomte's analysis this secretion contains,

Cascin and salts,
Fat,
Water,

23.23

10:47

66.30

Such milk-like secretions are by no means confined to the internal mucous membranes of birds. Jonge has made a most valuable research on the secretion of the glands known to anatomists as Glandula uropygi, situated at the tail of the common goose. The secretion was obtained in sufficient quantity for a complete qualitative and quantitative analysis, and although the analysis was not quite so complete as if a larger quantity had been obtainable, it fairly shows that there is a considerable analogy between milk and this secretion, the most marked difference being that no trace of milk-sugar could be found. The analyses of two samples were as follows:

*

Ash,

'Ueber das Secret der Talgdrüsen der Vögel und sein Verhältniss zu den fetthaltigen Hautsecreten der Saugthiere, insbesondere der Milch," Von D. de Jonge. Zeitschrift für physiol. Chemie, Von F. Hoppe-Seyler. Strasburg, 1879.