ore C, H. GOLDING-BIRD. 
normal human spleen, the lymphoid cells including coloured 
blood-corpuscles are relatively very rare; they are by no 
means so frequent as is generally represented, 
A DirrerentIAL Warm Stace. By C. H. Goipine-Brrp, 
B.A., M.B., F.R.C.S.E., Assistant-Surgeon, Guy’s Hos- 
pital, and Hon. Sec. Med. Mic. Society. 
Tue following is the description of a warm stage that 
appears to possess certain advantages over the simple copper 
one often employed, and to possess certain of those which 
belong to the more complicated arrangements where the heat 
is maintained by a constant stream of hot water. 
By ita fairly uniform temperature may be kept up for a 
long time, while any variation of sufficient importance to 
affect the specimen under examination may be at once 
observed and speedily corrected by simply moving the lamp 
by which the instrument is heated, and this is only necessary 
at long intervals as a rule. There is a great source of 
fallacy in the simple copper stage, where the heat is applied 
to a projecting copper wire, and in which cacao butter, placed 
on the metallic ring that is cemented to the glass slide, is 
used as the index of the temperature; for while the melt- 
ing of the cacao butter points to the copper ring having 
reached the temperature of the human body, it by no means 
follows that the centre of the small glass cover which is 
placed upon it, and which bears the specimen, is heated to 
the same degree. Experiment proves this to be the case, 
a much higher temperature than that of 98° F. being 
required for the stage before the glass cover upon it has 
actually reached the temperature of the blood, while the 
sudden fluctuations of the temperature are very frequent, 
and no longer to be registered when the cacao butter has 
once melted. 
The combination of two metals and the use of pieces of 
solid paraffin, placed at proper intervals, seem to overcome 
these difficulties... The instrument consists of a disc of 
copper, of the size and thickness of a halfpenny, in the centre 
of which a hole, three eighths of an inch across, is cut, while let 
into it on one edge (as shown in the accompanying woodcut), 
and firmly soldered, is an iron wire one tenth inch in diameter, 
1 The stage is made by Millikin, of St. Thomas’s Street, Southwark. 
