March 1, 1899.] Supplement to the " Tropical AgricuUumi." 
665 
efficient in cliecking growth of germ life than even 
a longer exposure applied later. 
If milk is allowed to stand for several day.s, it 
almost invariably undergoes a change thfit is 
known as souring. Its physical appearance is 
much altered, and the once valuable food is con- 
verted into a relatively worthless by-product. 
This change is a fermentative process that goes on 
in the milk, and is caused by a large group of 
different bacteria. These kinds are particularly 
numerous in stables and barns; moreover, they 
seem to find in milk such good surroundings that 
they grow with great rapidity. 
The sour taste of milk, so fermented, is due to 
the formation of lactic acid, that is produced by 
the splitting up of the milk sugar in the milk. As 
acid is formed in gradually increasing amounts the 
chemical reaction changes from a neutral to an 
acid condition. When the amount of acid formed 
approximates 0'6 per cent, the ca.^ein is unable to 
remain in its normal condition, and is precipitated, 
forming the solid curd that is characteristic of a 
sour-milk fermentation. The formation of acid 
does not go ot\ until the sugar of the milk is all 
decomposed, for the lactic acid bacteria are uuaLlj 
to grow where the amount of acid exceeds 0"8 
per cent. They are retarded, therefore, by the 
presence of their own by-products. 
Tlie souring of milk is so universal a pheno- 
menon that it is considered almost a natural and 
inevitable change in milk, and yet, if milk could 
be secured without bacteria, it would undergo no 
such change. 
No exception can be taken to the statement that 
milk is very apt to sour during a thunderstorm, 
This universal experience has led to the notion, 
thoroughly believed by many, that the cause of 
the souring is due to the action of thunder, or 
possibly the electric discharge. Experimental 
researches upon this question, however, fail to 
establish any such relationship. The passage of 
the electric spark through milk does not increase 
the acidity of the same. If bacterial growth is held 
in check in various ways, no atmospheric disturb- 
ance, as thunder or lightning has any effect. All 
the evidence indicates that the increased tendency 
toward the formation of lactic acid is due to the 
more favourable growth conditions that obtain at 
such a time. The warm, muggy atmosphere 
favours rapid germ development, and consequently 
the souring changes occur more quickly. 
A well-establislied rule of dairy practice is not 
to mix the night and morning's milk, or, to 
put it on a broader basis, fresh and old milk. 
Common experiences teaches that this mi.xture is 
apt to sour much more rapidly than where the 
two milks are left separate. The reason for this 
is a physical one, and is based on the difference in 
temperature of the two lots and the relation that 
these temperatures bear to the bacterial life that 
is contained in each milk. Under normal condi- 
tions the older the milk is the richer it is in germ 
life, but the night's milk is u.--ually cooler than tht 
niornitig's milk, which is relatively deficient in 
germ lilo. The mi.vtuio of the two lots raises the 
temperature of the whole mass, ond at the same 
time increases tlie germ content of the fresh milk 
80 that fermentative changes occur more rapidly. 
If night's milk at a temperature of 55 decrees 
Fahr. contains 1,000.000 b::c(eria per c.c, and the 
morning's milk, at a temperature of 80 degrees 
Fahr. has only 20,000 organisms per c.c, the 
mixture of the two in equal volume? would 'raise 
the temperature to about 65 degrees. 
At this temperature the 510,000 bneteria in the 
mixed milk would grow more rapidly than the 
1,000,000 at a lower temperature, and would 
tlierefore, sour the >niiie sooner. ' 
{To be continued.) 
TOBACCO. 
Mr. Xevill, Tobacco Expert, says that it is not 
at all necessary, nor is it a good thing, to select 
the richest lands for tobacco-growing. A ,^oil which 
will produce a splendid crop of maize, potatoe« 
lucerne, or sugar-cane is not necessarily a ^oil 
which will produce a good tobacco. In the Uni'ted 
States, tobacco is grown on lands whicli would not 
be thought worth cultivating in Queensland. The 
best soil for tobacco in Florida i^ a o-rey"«andv 
loam, underlaid by a stiff red or yellow clay sub- 
soil. Such land will require manuring. 
But what is the proper kind of manure to use? 
In Florida they say the best fertiliser is cotton- 
seed crushed and cotton-seed meal— the latter 
giving the plants a quick start ; the former by its 
slower action, feeding the plants at a later' p^Viod 
and sustaining them during the important crisis 
of leaf formation. About 80 t;o 100 bushels of 
crushed seed and 500 lb. to 800 lb, of the me il 
should be applied per acre. On land thus fertili'^ed 
the Sumatra tobacco yields on an averarre 800 lb' 
per acre, but as much as 1,300 lb. have been 
harvested on small, well-tilled holding-; Cuban 
tobacco will yield from 500 lb, to 900 lb on an 
average; the later yield is, however, exceptional. 
At the Queensland Agricultural College Mr 
Nevill is experimenting on two different soilsLone 
a heavy, deep, rich black loam ; the oi:her a poor 
sandy, shallow soil, overlying a rocky bottom' 
Unfortunately, the weather since and during the 
planting out time was exceptionally dry and a 
large proportion of the plants failed', but 'a good 
many are growing, and the gardeners are busy 
planting up the misses. 
"The analysis of a perfect tobacco fertiliser should 
be 10 to 12 per cent, potasii, 8 per cent, phosphoric 
acid, and 4 per cent, nitrogen. A Jamaica paper 
says that It IS quite impo.-sible to get this analysis 
outside a mineral fertiliser. ^Ye are not aware 
whether Mr. Nevill has used any fertiliser on the 
poor soil : but if not, probably next year, when the 
soil has been analysed, and when it is seen wiiatthe 
yield on the unfertilised land is like, he will turn 
his attention to e'cperiments in this direction 
although we know that he does not favour the use 
of fertilisers in t^jbacco-growing. 
If fertilising can be done cheaply, then there 
are thousands of acres, close to our largest cities 
and on the railway lines and rivers, which may 
yet be turned to account as tobacco plaututiona.— 
Queensland Agricultural Journal. 
