Bauhaus-Universität Weimar

Handbook for the Physiological Laboratory. Text
Burdon-Sanderson, John Scott E. Klein Michael Foster T. Lauder Brunton
nerve fibres. In tbe nictitating membrane and tongue of the frog, 
the plexuses which surround the capillaries may be seen to give 
out fibrils which enter the walls of the vessels themselves. For 
this purpose the tongue of the frog must be coloured in a half 
per cent, solution of chloride of gold, and used, after hardening in 
alcohol, for the preparation of sections. {See Chapter XII.) 
The development of blood-vessels will be given in the chapter 
on Embryology. 
Section III.-—Microscopical Study of the Circulation. 
Study of the Circulation in Cold-blooded Animals.—The 
parts which may be used for this purpose are (1) the web of 
the frog’s foot, (2) the mesentery of the frog or toad, (3) the 
tongue of the same animal, (4) the tadpole. 
Web of the Frog.—If the animal is not curarized, the ar¬ 
rangement must be employed which was described in Chapter 
III. It is, however, better to employ curare, as described 
in Chapter XVII. The animal is laid on an oblong plate 
of glass, on which a cork disk is fixed with sealing-wax, which 
should be three-tenths of an inch thick, and an inch and a quarter 
wide. The disk must have a hole in the middle, which should 
be about three-quarters of an inch wide. At the edges of this 
aperture pins are stuck, to which ligatures attached to the toes 
may be secured. 
Mesentery.—The preparation of the mesentery is not so 
simple. A snip is made in the right side of the belly, parallel 
with the middle line. Before dividing the skin further, it is 
raised to ascertain where there are no large veins; the incision is 
then continued upwards and downwards, in such directions as to 
avoid bleeding. If, notwithstanding, a vein is divided, the bleeding 
must be restrained by seizing the end of the incision with the clip- 
forceps. The traces of blood having been removed writh filter 
3aper, the muscles are divided in the same vertical line. This 
having been done, the intestine and mesentery are drawn out 
carefully, and laid on the anterior surface of the belly. The next 
step is to place the animal on a in Fig. 19. (For this, how¬ 
ever, a simple glass plate of similar size may be substituted, at 
the edge of which a cork is fixed, which should have an aperture 
corresponding to c, covered with a round cover-glass.) The frog 
having been pushed up against d, the intestine can be easily 
turned over on to b. The intestine then lies in the trough c, 
while the mesentery rests on the glass plate b. So much of the 
intestine as does not occupy the trough must be replaced. If 
the observation is prolonged (as in researches on inflammation), it 
is well to place in the trough, outside of the intestine, a layer of


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