172 
NOTES AND MEMORANDA. 
manner to the regular concentration of the blood by the evaporation 
of water from the surface of the skin. 
3. Experiments on the Wandering Cells in Living Tissues. — The ques- 
tion was, whether colourless corpuscles which have wandered outside 
the vessels are influenced in a similar manner by differences in concen- 
tration of the tissue-fluids. The cells which have wandered out into 
the tissue show the lively amoeboid changes of form and place, whilst, 
by infusion. of a 3 per cent, salt solution and evaporation from the 
skin, the amoeboid movements of the wandering cells becomes lower and 
very soon cease altogether. The same was observed with a 1 • 5 per 
cent, solution, the colourless corpuscles becoming round and shining, 
and changes of place could no longer be observed of them ; whilst 
with a 0 • 5 per cent, solution the changes both of form and place were 
very lively. Irrigation of the frog's tongue with salt solution of 
various strengths also produced important changes in the calibre of 
the blood-vessels and therefore on the rapidity of the blood-current. 
Under irrigation by a 0*5 per cent, solution, a very plentiful out-wan- 
dering, specially from the small veins, takes place, while in the same 
organ with a 1 * 6 per cent, solution, the wandering out of the colour- 
less corpuscles is completely suppressed. This solution acts first on 
the blood-vessels, producing a pronounced dilatation of the arteries, and 
therewith an acceleration of the blood-current in the arteries, capil- 
laries and veins, as Wharton Jones had already proved, and which, as 
H. Weber, F. Schuler, Buchheim, Vierordt, &c., showed, depends 
essentially on the diffusion of the blood-plasma with the salt solution. 
The acceleration of the blood-current is so considerable, that the 
venous current takes on part of the characteristics of the arterial one. 
Specially, the marginal position of the colourless corpuscles dis- 
appears. The second effect of the 1 • 5 per cent, solution of common 
salt is its influence on the changes of form and place of the colourless 
corpuscles. 
NOTES AND MEMOEANDA. 
Notes on Eecent Objectives.— The following observations are by 
Dr. J. A. Thacker, the editor of the Cincinnati 'Medical News' 
(January, 1875), and have a certain interest for our readers: "Dr. 
J. G. Richardson, Microscopist to the Pennsylvania Hospital, read 
a paper before the Biological and Microscopical Section of the 
Academy of Natural Sciences, entitled ' Notes on the Performance of 
Two One-Fiftieth Objectives.' One of the glasses was an immersion, 
by Tolles, and the other a dry one, by Powell and Lealand. Whether 
the object of the comparison was to determine the relative merits of 
the work of the makers is not stated ; but if it were, certainly the 
mode adopted was very improper. An immersion lens should be com- 
pared with an immersion, a dry one with a dry one. It is as unfair 
to compare a wet with a dry objective, as it is to compare an eighth 
