December 16,1871.] THE PHARMACEUTICAL JOURNAL AND TRANSACTIONS. 
4S3 
structure producing the interference, and find these 
very phenomena a great help instead of a plague 
and a torment. 
A class of phenomena accompanying the use of 
“oblique illumination” should be considered here, 
but we must confine ourselves to pointing out the 
form the errors generally assume. The phenomena 
are strictly analogous to the second images seen when 
the image of an object is viewed in a thick look¬ 
ing-glass, and were, of course, due to successive re¬ 
flections from the different surfaces of the mirror and 
its metallic coating. When such objects as diatoms 
are viewed by very oblique light from the mirror, 
these secondary images are very numerous, arising 
from successive reflections from the surfaces of the 
thin cover, glass slide, the object itself, and the 
medium in which it is mounted. These successive 
reflections produce the appearance known as false 
striae, and may be detected by slightly changing the 
angle of incidence of the illuminating pencil, or by 
rotating the object in a horizontal plane. 
Molecular Movements. —We must notice these 
very briefly, as our space has nearly run out. These, 
called often after their discoverer, Brownian move¬ 
ments, are hardly to be distinguished from those 
more properly called vital by any other than an ex¬ 
perienced microscopist. Indigo, carmine or gam¬ 
boge rubbed up in water is admirably adapted to 
show the movements, and a careful study of them 
will be the surest means of enabling the student to 
recognize them. Their want of power of choice (i. e. 
their movements are purely mechanical) is, perhaps, 
their sole distinguishing feature. The differences 
between Brownian and vital movements in small par¬ 
ticles are so slight, that it is doubtful whether they 
can be described, or that anything but experience 
will enable the student to distinguish between them. 
Certain sources of error of interpretation arising 
out of the use of the micro-polariscope and micro- 
spectroscope, must be deferred, as must also the dis¬ 
cussion of a few other points with reference to the use 
of the ordinary stand. Enough has, it is hoped, 
been said to be of use to the student in microscopy, 
who, like the author, in his younger days especially, 
is pretty often at his wits’ ends. 
COD-LIVER OIL, ITS MANUFACTURE 
AND [COMMERCE. 
BY P. L. SIMMOXDS. 
(Concluded from page 444.) 
In the Journal de Pharmacie for March 1800, 
my brother-in-law, Dr. Soubeiran, gave a descrip¬ 
tion, with illustrations, of the apparatus and pro¬ 
cesses of manufacturing the oil which he found in 
operation in Norway, during his visit to the Bergen 
Fishery Exhibition. These seem to be chiefly two, 
one employed in many small establishments in Nord- 
land, by which steam is conveyed by pipes from a 
boiler into closed casks containing the livers. These 
casks have cocks placed at different heights to draw 
oft’the oil as dissolved; the oil first obtained is much 
lighter in colour than that which comes away at the 
close of the operation. By this process a milky and 
turbid oil is obtained, without any bad taste, but 
which is less esteemed than that procured by more 
improved processes, as it is less rich in iodine and 
bromine principles, which become dissolved in the 
water introduced into the middle of the livers. To 
obviate this defect, in the larger number of factories 
established in Norway the livers are heated in 
boilers with double bottoms, which receive the steam, 
and in which the filtration proceeds slowly under 
the influence of heat. When the livers yield no 
more light oil, they are removed to a caldron hold¬ 
ing from three to four barrels, and heated by fire, 
when a darker oil is obtained of which the Nor¬ 
wegians make great use for lighting purposes. After 
this the heat is increased, and, by boiling for about 
ten hours, the brown oil is obtained which is used 
for various industrial purposes. The resinous-look¬ 
ing residue is sold at about os. the barrel for manure. 
Unless care is taken in the selection of the livers 
and the preparation of the oil, it will often have 
an unpleasant flavour. Thus the liver of the coal- 
fish ( Gadus carbonarius ) does not possess the pure 
flavour and peculiar properties of the true cod-liver 
oil, and the livers of some of the cod caught late in 
the season, which have fed on the capelin ( Mallotus 
gramlandicus) , yield an oil far from agreeable, and 
of a totally different flavour. 
On the coast of North America many cod are 
caught with diseased livers, that evidence of a dis¬ 
ordered or weak stomach. The sick fish are called 
“logies,” from the heavy, lifeless feel of them on 
the line as they are drawn up from the bottom. 
The livers of logy cod are always more or less dis¬ 
eased. They are destitute of oil and of a dark 
colour, and not unfrequently contain abscesses filled 
with pus. Young fish are very rarely found to be 
inwardly diseased, so that, perhaps, after all the 
logies are aged individuals, whose vital organs are 
impaired by the gradual decay of nature. 
Attention has been drawn from time to time to 
other fisli-oils which might be used medicinally, but 
looking at the abundance of cod-liver oil in the 
two great seats of production, there seems little 
necessity for resorting to these, unless, perhaps, 
in India and Australia, where a native product 
might be more easily and cheaply obtained. The 
oil obtained from a small fish called the oolachan, 
abundant about Vancouver’s Island, and the oil ob¬ 
tained from the Halicore JDugong have been recom¬ 
mended as substitutes for cod-liver oil. 
Several years ago Mr. Gobley, of the School of 
Pharmacy, was engaged at Paris in preparing a medi¬ 
cinal oil from the liver of the ray, which was said to 
be much less disagreeable in flavour and odour than 
cod-liver oil. About the same time Professor Owen 
drew attention, in his course of lectures, to the ser¬ 
vices that might be rendered to medicine by the 
livers of the numerous sharks and dog-fish which 
are met with on our coasts, and especially in the 
equatorial seas, and which are generally rejected by 
fishermen. The advice of Professor Owen seems to 
have been followed, for in many localities, as on the 
coast of Norway, Canada, Australia and the Indian 
seas, the shark fishery is carried on largely for the 
oil obtained. The shark fishery of Norway yields 
annually 5000 barrels of liver. 
In India, shark oil from the liver is prepared in 
great quantity at the ports of Mangalore and Til- 
lichery, and an extensive fishery is carried on at 
Bombay; twenty years ago as much as 700,000 
gallons of this oil was shipped from the ports of the 
Madras Presidency. M. Collas, principal naval 
surgeon and chief of the health establishments in 
