222 
NOTES AND MEMOKANDA. 
but I have found the little home-made apparatus here described very 
satisfactory in conquering this difficulty. 
Two bullets are slightly flattened at one point by a few light blows 
with a hammer, so that they will stand on this flattened part without 
any tendency to roll. A piece of No. 16 iron wire, half an inch long, 
and sharpened at one end, is driven into the opposite part of each 
bullet for a handle. A gash, i inch deep, is also cut in the side of 
each, which may be readily done with a hammer and a stout-bladed 
pocket-knife. A strip of tin-plate, ^ inch wide and 2 inches long, 
is cut, and each end of the strip is thrust in the gash in a bullet, 
where the tin can be firmly secured by hammering the gash together 
with the sharp edge of a tack-hammer, or other suitable tool. A cube 
of cork is cemented at the middle of the under side of the tin strip, 
of such thickness that it will touch the covering glass when in use, 
and a varied pressure can be obtained from the weight of the bullets 
by slightly bending the tin strips up or down, before the apparatus is 
placed in position. Care should be taken that each bullet just touches 
the glass, in which case the slight springing of the tin strips will act 
as a lever, with the cork as a fulcrum; and if more pressure is 
needed, it can be had by placing an additional weight on the cork. 
The advantages of this method are, that nothing projects beyond 
the edges of the glass slip, to take up unnecessary room or receive 
any accidental disturbing blow ; and if the double weight is applied 
while the slide is cool, and the balsam slightly stiffened, even if the 
top of the hot- water bath is not perfectly level, the covering glass 
will be securely kept for any desired time, without the slightest 
change from its original position. 
The best Mode of examining^ the Umbilical Cord of Mammalia. 
— Mr. Lawson Tait, who has recently read a very valuable paper on 
the structure of the cord before the Royal Society,* gives the follow- 
ing as the best mode of preparing specimens. He says : — First of all 
I may say that I have in no instance drawn a conclusion from obser- 
vations made on a cord otherwise than perfectly fresh, unless it is 
distinctly stated to the contrary. I have found the examination and 
treatment of tissue which has been subjected to hardening reagents 
so unsatisfactory that I have quite discarded it. 
All my sections are made by the freezing process (described in 
Humphrey and Turner's Journal for May, 1875), so that sections of 
the perfectly fresh cord of about -^^^ of an inch in thickness have 
been examined. These have been subjected to various treatments— as 
simple clearing by glycerine, destruction by acetic acid, staining by 
silver lactate, and by my various indifferent staining fluids, hsema- 
toxylin, litmus, cabbage, &c. (also described in Humphrey and Turner's 
Journal). 
My injecting apparatus is so arranged that it acts automatically 
when set at work. The tissue injected and the whole apparatus is 
surrounded by a current of warm water, the temperature of which is 
registered. The injecting force is supplied by compressed air ad- 
* ' Proceedings of the Boyal Society,' No. ^68. 
