68 
Supplement to the " Tropical Agriculturist." [July 1, 1893. 
commoa cheese-mite, another well-knowu species 
being A. Destructor which feedti on zoological 
specimens and thus causes much annoyance to 
the naturalist. Sarcoptes scabei, another mite, 
is the cause of the skin-disease known as "itch." 
Mange in the domestic animals is due to three 
genera of Acari, viz., psoroptes or deruiatodecte.'^, 
symbiotes and sarcoptes. The true ticks (ixodidu') 
attach themselves parasitically by means of their 
suctorial mouths to the bodies of various mam- 
mals, such as liorses, sheep, oxen un>l di>„'.s. 
Another member of the Acarina is the curious 
little Demodex folliculorum which is found in the 
sebacjous follicles of man, especially in the 
neighbourhood of the nose. " It is probable," 
says Dr. Nicholson, "that few, if any in- 
dividuals are e.vempt from this iiarmless parasite." 
The Myriapoda are articulate animals in 
■which the head is distinct and the remainder 
of the body is divided into nearly similar 
segments. They have one pair of antenti:e or 
feelers, and the number of legs is always more 
than eight pairs. The centipedes and millepedes 
are included among them. 
THE LISTER-BABCOK MILK TESTER. 
This new apparatus was invented by Professor 
Babcock, Chief Chemist of the Agriculture Ex- 
perimental Station of AVisconsin, U. S. A,, whose 
English Agents are Messrs. R. A. Lister and 
Company. The following is an accouat of how 
the percentage of butter fat in milk is tested : — 
First, thoroughly mix the mass by pouring from 
one vessel into another, or by stirring, and then 
■with the pipette secure the sample and put in 
a testing bottle. Add an equal volume of 
commercial sulphuric acid that has been kept 
stoppered, of 1^843 specitic gravity. By a gentle 
rotary motion thoroughly mix the acid and 
milk. Then place the bottles in machine and 
turn for ten minutes, at a speed of eighty-six 
to ninety turns of the handle per minute, then 
stop, and fill the tank with water at a tem- 
perature of 190 degrees Fahr., and at the same 
time fill bottles to the 7 per cent, mark with 
water of the same temperature. This may be 
taken with the pipette from the hotwater tank 
(be careful not to havg. the water above 190 
degrees as it may burst the bottles); when this 
is done, put the bottles back into machine, and 
turn it again for two minutes, the bottles can 
then be taken out, held in a vertical position, 
and the amount of butter fat read off in the 
graduated tube. It may be 'S '2, 4r'4, or o-6, or 
more or less, and this determines the value of 
the milk, just as the assayer fixes the value of 
ores by testing samples. 
At the recent Dairj^ Conference, Professor 
Primrose McConnel elicited the hearty plaudits 
of the company when he referred to the Babcock 
tester as a most reliable test of the percentage 
ot butter fat in milk. By means of this new^ 
tester, together with a hydrometer aiid special 
set of tables arranged by Mr. Enibrey. F.c.s., 
City Analyst, Gloucester, any one can easily 
determine for himself with tlie greatest accuracy 
not only the percentage of fat in his milk but 
dlso of solids not fat, so that he thus obtains an 
ftualysis of jjiiJk, Tiii? tester was en- 
tered for competition at the London Dairy Show, 
and Mr. (iilljcrt Murray, the well-knowu expert 
at Elvjston, Deiby^bire, was ujipointed Ity the 
British Dairy Farmer's Asiiociuliou to test the 
appliance. For this purpose lie provided Messrs. 
laster with three diftt-rent qualities of milk — one 
being very rich, having been drawn from the lirtit 
prize .\ldorney cow in the show, one Ijeing tukeu 
from an ordinary cow in the show, and «ue being 
newly-sei>arated milk. The three milks were 
duly tested by the Lister-Babcock teeter and 
the results noted. Samples of the same milk 
were then sent to the Society's Chemist, Pro- 
fessor Llyod, to be analysed in the usual way, 
and the accuracy of the analysis of the milks 
obtained by the tester was so fully borne out 
by Mr. Llyod's analysis, that a special silver 
medul was awarded to Mes6r^. Lii-ter for this 
valuable ajijdiance. Tiie apparatus has also 
been tried in New South \N'ales, where the 
following conclusions were drawn by the autho- 
rities by whom the trial was conducted:— 
1. The Babcock machine may be relied on 
to give uniform and concordant results within 
a limit of one-fifth per cent. 
'z. Its results do not differ from those obtained 
by extraction with ether by more than one-fifth 
per cent. 
6. The prolonged contact of the acid with 
the milk in the bottle liefore whirling ha* no 
effect upon the reading of the butter fat within 
the limits of time occupied by the t«st. ISbould 
the acid have remained for any great length 
of time in contact with the milk, the tank must 
be filled with hot water. In any case, we 
consider the readings are more reliable if hot 
water be added during whirliug, but if the 
filling be done expeditiously, and the bottles 
rotated at once, the initial temperature is 
sufficient. 
4. Scrupulous attention to the detailed in- 
structions is absolutely essential, us are also 
strict cleanliness and accuracy. 
6. The machine is sound in principle and 
easy to understand and to work. 
6. The time required for the treatment of 
twenty-four samples is about one and-a-half 
hours from the filling of the first bottle to 
the reading of the last. Forty-eight samples 
may be done in two hours if two men of^ 
working. We would, however, always advif* 
that each milk be tested in duplicate. Thus 
fifty samples could be treated in about three hours. 
7. The cost of the acid used for charging 
twenty-four bottles is about 3d. Commercial 
sulphuric acid may be used, but it is important 
that it should be of the right strength. Its 
specific gravity should not be much more or 
less than 1-834. 
8. It has the great advantage over gravimetric 
methods that it is more expeditious, and does 
not require any special skill in the manipula- 
tion ; accuracy and cleanliness are absolutely 
essential. It should, in our opinion, prove of 
great use in butter factories. "With a ready and 
effective means of testing the quality of the 
milk supplied, both buyers and sellers would 
be benefited, as a fair scale of payment, 
according to the richness of the milk, could 
be ftdoptecl, 
