204: 
precisely with the observations of Engelmann, for which the 
latter claims an independent position. ‘There is also an ac- 
count of the better known structures in the tongue of the frog, 
which have been traced into direct continuity with nerve- 
fibres, as is not yet the case with those of mammalia. 
Terminations of Nerves in Glands.—We have more than 
once noticed the investigations of observers who have endea- 
voured to repeat, for themselves, the observation of Pfliiger on 
the terminations of nerve-fibres in the cells of salivary glands 
and other glandular organs, and who have, in most cases, 
failed entirely to confirm his results. These negative results 
have, of course, been announced and received with that 
amount of hesitation which is unavoidable in rejecting the 
conclusions of so trustworthy and experienced an observer as 
Pfliiger ; and the more because it has not been certain that 
other observers have used precisely the same process as he did. 
Great interest, therefore, attaches to a paper recently pub- . 
lished by Pfliiger himself, in his own ‘ Archiv,’ 1871, Ites 
Heft, p. 50, in which he gives a summary reply to his critics, 
and at length, what is more important, describes the methods 
by which his results were obtained. Against his assertion 
that medullated nerve-fibres can be traced to end directly 
in the salivary glandular epithelium, the following objec- 
tions have been made; which, with his replies, we give as 
literally as possible. 
First oljection—The fibres figured by Pfliiger are said to 
be capillary vessels; but (a) the fibres are stained bluish-black 
or coal-black by the application of osmic acid, while capillary 
vessels are quite uncoloured; (0) the threads figured, some- 
times have a degree of fineness never seen in capillary vessels ; 
(c) these fibres are directly continuous with the glandular 
epithelium, and not merely applied to its surface, as must be 
the case with capillary vessels ; (d) these fibres often lie packed 
together in bundles, and surrounded by a sheath (neurilemma), 
which is not the case with capillary vessels; (e) the minute 
structure of these fibres differs from that of capillary vessels, 
precisely as a medullated nerve-fibre differs from a capillary 
vessel. 
Second olyection.—The fibres in question are said to be 
mucous threads; but (a) threads of mucus do not blacken 
with osmic acid as nerve-fibres do; (0) threads of mucus 
cannot occur where there is no mucous substance; and these 
fibres have been seen in the submaxillary gland of the rabbit, 
which Heidenhain has shown not to be a mucous gland; (ce) 
were these fibres mucous threads, they could have no detached 
sheath enclosing them ; (d) if they were mucous threads, they 
