MAGAZINE OF SCIENCE AND AFT. 
134 
Tiie poison gland will next occupy our attention, j 
and as tlis specimens which I have examined differ j 
in many respects from the structure of the gland as i 
described by Professor Muller, in his great work on 
the glandular system, I have extracted the para- 
graph in which he explains it. He says—“ It 
consists of a number of elongated narrow lobes, i 
extending from the main duct, which runs along 
the lower border of the gland; each lobe gives oil 
lobules throughout its exteut, thus presenting a 
pimiatifled structure: and each lobule is divided 
into secerning cosea, which constitutes the ultimate 
structure of the gland." 
The poison gland lies immediately under the 
skin, on the side of live bead posterior to the eye, 
as seen in fig. 1, and its duct passes forward under 
the orbit, to the anterior and external surface of the 
aponeurotic fang sheath; each gland is,in an adult 
death adder, about tlie size and shape of a small 
almond, the apex being placed anteriorly; the pos¬ 
terior half is covered by the muscles of mastication 
and the compressor muscle, which also extends 
diagonally across the roof of the mouth ; it posseses 
a dense aponeurotic sheath, of wavy, shining, and 
fibrous tissue (Fig. 1, /.), between which and tile 
skin is a close network of rather large blood vessels. 
The gland itself is highly vascular; when a trans¬ 
verse section of an injected specimen is magnified, 
it has tile appearance of a sponge. The structure, 
as found in the snakes of this country, is simple, 
and may be explained in a few words. Tracing the 
duct backwards into the body of the gland, it is 
seen to divide into tubes, which agaiu divide; this 
subdivision continues until the terminal tubules 
end in a minute closed sac ; these are con¬ 
nected by a fibrous matrix, in which capillary 
blood vessels are most freely distributed. The 
terminal tubules are, by means of a high power, 
seen to he lined with a structure-less thin mem¬ 
brane, under which basement cells are placed, 
forming the mass of the walls. 
It is evident, from the nature of this structure, 
the large supply of blood it is capable of receiving, 
and the elastic nature of its aponeurotic covering, 
that it is formed to secrete a large, quantity of its 
peculiar fluid in a short space of time. 
The aponeurotic fang sheath (Fig. is readily 
seen, upon opening the mouth of a venomous snake; 
it covers the fangs, encloses the loose mucous tis¬ 
sue, which surrounds the supplemental and rudi¬ 
mentary fangs, and possesses a wide base. In some 
specimens, as the death adder, its fimbriated open¬ 
ing is confined to the apex; in others, a fissured 
opening extends posteriorly from the apex to the 
base; the central coat is composed of elastic, 
fibrous tissue, and is attached only at the base, 
being covered, on both the external and internal 
surfaces, by a continuation of the mucous membrane 
of the mouth. 
'When this aponeurotic sheath is reflected back, 
in a well injected specimen, the lax and highly 
vascular mucous membrane, in which the supple¬ 
mental and rudimentary fangs lie embedded, comes 
into view, and forms a beautiful object, when seen 
under the microscope with a with a full light and a 
low power: it is then found to consist ot a mass of in¬ 
tensely vascular mucous membrane, reflected from 
the internal surface of the aponeurotic fang-bag and 
freely covering, by ample folds, the rudimentary 
and supplemental fangs ; the functional fang is not 
embedded in this loose mass of membrane. 
The duct is externally large, and unattached in 
its course to the fang bag, with the exception of a 
loose connection with the upper lip; the walls are 
very thick, leaving the canal in the centre, for the 
transmission of the poison, very small; the struc¬ 
ture is elastic tissue. Anteriorly it expand 
upon the lower portion of the external ami anterior 
surface of the fling sheath, becoming blended, if 
not continuous, with its structure. 
The manner in which the duct communicates 
with the functional fang tube, as well as with those 
of the supplemental and rudimentary fangs, lias 
not been yet made out; hut 1 hope, in my next 
paper, to be able to explain this. 
The retractor maxillaris (Fig. 1 and 2, <1.) muscle 
is a portion of the poison apparatus, which does 
not appear to have received the attention which its 
importance deserves. It arises from the base of the 
side and inferior portion of the head and lower jaw, 
and is inserted principally into the ptcregoid bone, 
but also into the external surface of the palatine 
bones. The comparative dimensions of this muscle 
are very great, and its action is powerfully to retract 
the superior maxillary and palatine bones, and 
through them their fangs and teeth. 
flaying now completed the general and structural 
devseription of the poison apparatus, I must invite 
attention to the relative character of the superior 
maxillary hones in snakes more or less venomous. 
Fig. 3 is the superior maxillary bone of a small 
ringed snake ; fig. 4, of a black snake; and fig. 5, 
of a death adder. 
In these, there is a gradual transition, more or 
less, from a short and broad, to a long and narrow 
hone, as well as from a broad and horizontal, to a 
narrow and diagonal articulating surface. 
So far as I have observed, these are instances of 
a general rule, viz., that iu proportion to the veno¬ 
mous quality of the snake, is the shortness and 
breadth of this bone, as well as tlie large size and 
horizontal position of its articulating sui face. 
Let us now observe tlie position of the fang in 
relation to its maxillary hone, as seen in fig. 6, and 
the character and position of the above-mentioned 
articulating surface, when placed in its relative 
position with the other parts of the head. It will 
then appear evident, that any amount of anterior 
and posterior movement of the maxillary upon the 
malar bone, can, in no material degree, influence 
the position of the point of the fang, in relation to 
any substance that-may be in the mouth; and, fur¬ 
ther, that if in the less poisonous serpents, a move- 
I ment of the maxillary hone forwards would, from 
the slight curve of the articulating surface, render 
the fang slightly more perpendicular, its position, 
when retracted, would still be such, that the point 
must enter whatever the mouth contained, if pressed 
upon it. But we, moreover, And, that the more 
venomous the snake, tlie more perfectly flat, hori¬ 
zontal, and extensive is the articulating surface, 
and, therefore, the less does the fang tend, in any 
movement of the maxillary hone, to alter its rela¬ 
tive position. 
When describing the structure of the poison 
gland, we were led to the conclusion that it was 
formed to secrete a large quantity of fluid in a short 
space of time; we also found that the means for the 
exit of this, viz., the fang tube was small, and we 
know that the offensive bite of a snake is instan¬ 
taneous. 
We have seen that the retractor maxillaris mus¬ 
cle is very large and powerful in venomous snakes, 
and that their action is directed, so as to retract 
