218 PROFESSOR FRANK J. COLE 
be watched precipitating as it travels through the vessels,—serial sections can be cut of 
the tissues; and as far as the finer vessels are concerned, this injection is as satisfactory 
asany. An additional advantage is that it exercises no staining effect on the tissues, nor 
is it itself stained by histological dyes. The walls of the vessels can therefore be stained 
red, and preparations obtained which are both clear and convincing. The only objection 
to its use —and it is unfortunately a serious one—is its tendency to precipitate during 
the operation by combining with the organic fluids with which it is brought into contact, 
and therefore to block in the smaller vessels. This may be avoided by thoroughly 
washing out the vessels before throwing in the blue—an important precaution, since the 
precipitate is of a clinging, flocculent, obstructive nature. I find it convenient to use a 
cannula with a double lead. ‘Two different fluids can then be employed successively 
without unshipping the cannula. 
9. GENERAL ANATOMY OF THE Parts. 
The ventral or cardiac aorta of Myxine (fig. 1, c. ao.) courses directly forward from 
the ventricle of the heart (vent.), giving off on each side as it goes along the afferent 
branchial arteries (af. b7.). ‘The walls of the latter have capillaries, and are in fact 
richly vascular. ach afferent vessel passes straight up to its gill, and enters it below 
and slightly behind the exit of the efferent gill duct. 
Examination of a large number of specimens reveals peculiarities in the first and 
last afferent branchial arteries * which are of very common, even if not of universal, 
occurrence. The former, on its way up to the gill, gives off a very short anterior twig 
(fig. 1, *), which varies somewhat in its structure, but is always blind and connected 
with the neighbouring tissues by one or more fine but strong threads. We know from 
StockaRrp’s work that a hyomandibular and two post-hyomandibular clefts develop and 
then degenerate between the mouth and the first functional gill of Bdellostoma, and it 
is therefore possible that this twig may represent the vestiges of the arterial supply of 
these structures. An additional reason for this view is found in the variations: of the 
twig itself. Sometimes there is more than one arising from the arterial trunk, and when 
that occurs they soon meet and fuse. Or the twig may give off some branches large 
enough to be easily recognisable. Or, most important of all, it may terminate in a 
capillary network: or rete marable, which thus represents all that is left of the gill. 
This network, when present, is situated in a pear-shaped expansion at the extremity of 
the twig, and the network itself is easily demonstrable by injection. I have never found 
any traces of an opening to this twig, and we note that it is situated further down on 
the arch than the vascular papille. I therefore consider it to represent a different type 
of structure, although it may not be homologous in all specimens. 
J. Miuier, who noticed this structure both in Bdellostoma and Myzxine,t finds in 
the Cape Bdellostoma a connection between it and the carotid system by means of a— 
* The most anterior or first gill is supplied by the first afferent branchial artery, and so on. 
t Abh. Ak. Berlin, Jahr 1839, p. 191. 
« Wheat (ck, > 4. 
