1887.] MICROSCOPICAL JOURNAL. 213 
its source—the burner—is radiated into the surrounding air at an equally 
constant rate, and, as one passes towards the wide end of the plate from the 
burner, trials with the thermometer show that there may be found an infinite 
number of points in succession at which the temperature is very nearly con- 
stant. 
In order to use the paraffin itself as an indicator of the proper temperature 
a new type of cup in which to melt the paraffin was employed—a trough, 
made of copper, tin-lined, and 6 in. long, 14 in. wide, and 1} in. deep. In 
practice the cup is half filled with paraffin and placed lengthwise on the cop- 
per plate, with its narrowest side towards the flame, and about g in. from it. 
The paraffin cup may be covered with a:strip of glass to exclude dust. If 
the burner plays upon the plate as directed, and the trough is in the proper 
position, in about an hour it will be found that the paraffin in the trough has 
been melted at the end nearest the burner, but has remained congealed at the 
other. Moreover, it will be found that the point where the melted comes in 
contact with the nearly frozen paraffin is very constant, and it is just at this 
point where it is safe to place objects which are to be imbedded. __ 
It is clear, from what has preceded, that a shorter cup or trough filled 
with soft paraffin melting at 36° C. may be placed still farther away from 
the burner, alongside of the vessel containing hard paraffin fusing at 56° C., 
while mixtures of turpentine and paraffin, or chloroform and paraffin, would 
remain molten at a still greater distance from the flame. 
The applications and possibilities of this new device will be readily ap- 
preciated by histologists and embryologists, since it can be quickly seen if 
objects are in danger from overheating by simply noting whether the point, 
where the paraffin remains molten in the trough, has advanced farther from 
the flame. ‘This can be easily observed through the transparent cover of the 
troush. 
For large laboratories, where a number of students are engaged in im- 
bedding, a simple modification of this device suggests itself. For sucha 
purpose a horizontal disk of sheet-copper, of the same thickness, but 3 ft. in 
diameter, would afford room for a large number of paraffin imbedding- 
troughs, which could be arranged in a circle around, and some distance from 
the centre, at which point a larger burner would be applied underneath. 
The temperature in such a device would diminish from the centre towards 
the periphery of the disc. The troughs would be placed upon different 
radii upon the surface of the disc, just as two or three troughs may be 
placed upon different radii of the triangular plate, which is practically the 
sector of a disc, as described above. For imbedding delicate objects, small 
cups made of tinfoil, pressed into shape in circular, tapering moulds, may 
be satisfactorily employed with this apparatus, in the same way as the 
troughs. The device described above can be made by any coppersmith for 
about two dollars. 
————( ) — 
Nerves in the Liver.—Mr. A. B. Macallum, of Toronto, Canada, 
presents (7 9. J. Micros. Scz., v. 27, p. 439) the results of his studies upon 
the termination of nerves in the liver. These studies were made upon the 
amphibian Vecturas and upon the human liver, and studies which were less 
satisfactory were based upon material from dog, rabbit, and frog. In studies 
on lVecturus, the following method was employed:—pieces of liver were 
hardened for a week or more in Ehrlich’s fluid, or for several days in 1-1 % 
chromic acid solution. Sections cut with freezing microtome were placed 
in a weak solution of formic acid (5 ) for one hour, transferred to a 1% 
solution of gold chloride for 20 minutes, then washed in distilled water, 
and the gold afterward reduced in the dark with a 10% solution of formic 
