General Science. 
419 
and the celerity with which they follow each other ; and as many 
of the most active medicines now in use, and prescribed in this 
way, are virulent poisons, much uncertainty, and even danger 
may arise from it. 
“ The late Dr Black, with a view to obviate the inconvenience 
arising from this vague and indefinite manner of ascertaining 
small doses of tinct. of opium, &c. proposed that the lips of the 
phials kept in the apothecaries shop for this purpose should be 
ground to a certain thickness. More lately, the College of Phy- 
sicians in London, has sanctioned the use of a slender tube, gra- 
duated in a particular manner, known by the name of Lane’s 
Drop Measure. At first sight, this tube may be supposed to 
answer the purpose ; but, in charitable institutions and extensive 
pharmaceutical practice, its use appears to me to be attended 
with many inconveniences : as, when employed, it is to be im- 
mersed to the requisite depth into the fluid designed to be mea- 
sured, it is plain that the fluid must be first poured from the 
bottle in which it is kept, into some convenient vessel fit for the 
immersion of the tube. Besides, in so slender a tube, and con- 
sequently of very considerable length, it is obvious that a good 
deal of the fluid will adhere to its external surface, which must 
fall along with the contents into the phial which it is to be trans- 
ferred to, giving rise to much uncertainty and inconvenience. This 
can only be avoided by wiping the tube after every immersion, 
which produces great delay. With the view of obviating these late 
inconveniences, I have constructed the measure represented in 
Fig. 17. of Plate VII. It resembles the conical glass measure 
of the London College ; but, in place of being closed, the lower 
part is drawn out to a slender tube, fitted for being graduated, 
and the end of this is provided with a stop-cock DE, to prevent 
the exit of the fluid to be measured, until the quantity required 
be accurately ascertained. This measure is graduated from 2 
ounces down to 5 grains ; and, by a little more nicety in the 
blowing, it might be carried still lower. The stop-cock has a 
hole in it, m n, which permits the fluid to escape, when it is 
turned, as in the figure. By means of this apparatus, a small 
quantity of any fluid may be correctly measured and transferred 
to a phial, or any other vessel, with no greater loss than arises 
in passing through an ordinary funnel.” 
