304 
been inclined to ascribe the contraction of the gland to a 
direct action of the nerve on the proper gland-cells. In the 
larger cutaneous glands of the frog, smooth muscle-fibres 
have been described by Szczesny and Ciaccio, also in the 
smaller ones surrounding the gland-cells and enclosed by 
the tunica propria of the gland, which tunica appears to be 
of an areolar character. Eberth in the paper above noticed 
figures the smooth muscle-cells as seen in sections of the 
glands, but remarks curiously enough that he has failed to 
detect them in the glands occurring in the swimming mem- 
brane of the foot. There can, however, be little doubt that 
they are represented there, and it is through the contraction 
of these proper contractile elements that the change in the 
dimensions of the glands is effected. Engelmann has, it is 
said, more recently observed elongated cells in the cutaneous 
glands of the foot, to which he attributes the contractile 
property, and which, doubtless, correspond to the pre- 
viously described smooth muscular fibres. Szczesny says 
that some of these muscular fibres exhibit cross-striping, 
but Eberth cannot confirm him in this; such markings are 
due to plications and not to differentiation of the cell-sub- 
stance. 
The nerves of the cutaneous glands first mentioned by 
Ciaccio are described and figured in Eberth’s paper. A very 
fine network of nerves is described by him lying close round 
the gland-cells, the points of intersection of the fibres having 
often spindle-shaped nuclei. From this fine net-work, which 
is not due to any deceptive appearance of the intermediate 
substance of the gland-cell, since it is brought to view by 
dilute acetic acid, which shrinks up the gland-cells, proceed 
still finer fibres which appear to pass to the gland-cells, 
whether entering into direct connection with them or not 
Eberth does not say. Here, again, the histologist is baffled 
in attempting to determine the connection of nerve- and 
gland-elements. It is, however, clear that Eberth’s thoroughly 
trustworthy observations do not tend to confirm the view of 
an abrupt junction of nerve- and gland-element as maintained 
by Pfluger for the liver and salivary glands. 
Retina.— Landolt (M. Schultze’s ‘ Archiv,’ Bd. vii, 81) has 
studied the retina of the frog on preparations made with the 
help of osmic acid, especially of the stiitzgewebe. 
He confirms generally the observations of M. Schultze (in 
his ‘ Archiv,’ Bd. ii, s. 267). 
Another research on the retina of the frog appears in 
Reichert and Dubois-Reymond’s ‘ Archiv,’ 1870, p. 642, by 
Dr. Merkel, who worked independently of Landolt, but finds 
