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AN-END—ANEURISM. 
  
  
  
its chances of double fare. A new mouth, furnished 
with two rows of numerous tentacula, was opened 
up on what had been the base, and led to the under- 
stomach : the individual had indeed become a sort 
of Siamese twin, but with greater intimacy and 
extent in its unions. (Brittsh Zoophytes, i. 235.) 
As inmates of the aquarium, sea-anemones are 
apt to prey upon their fellow-prisoners. ¢Simple 
contact of the tentacula,’ says Sir J. G. Dalyell, ¢is 
the prelude of destruction. Some animals, as if 
conscious of their inevitable fate, seem paralysed by 
the touch, and yield without a struggle. thers, 
whose size and strength should insure indemnity, are 
held in the relentless grasp; the tentacula crowding 
faster and faster around, until the victim is speedily 
swallowéd alive” There appears to be in other 
marine animals an instinctive horror of the tenta- 
cula of the sea-A. The hermit-crab will instan- 
taneously flee out of its shell, if the shell is caught 
by them. It is now believed that, like the Acalephe 
(q- v.) and the Hydras (q. v.), the sea-anemones 
possess a power of benumbing their prey. Sea- 
worms (Nereides) have been observed first to writhe, 
and then to become paralysed. Little elliptical 
capsules are in some species scattered over the 
whole surface of the body; in others, confined 
to the tentacula, or even to their tips. These are 
furnished with spicula or minute spears, by which it 
is probable that not only are wounds inflicted, but 
poison is also conveyed into them. The sensations 
produced by the touch of the tentacula appear to be 
very different in the case of different persons, from 
a mere ‘rasping feeling’ on the withdrawal of the 
hand, to a slight tingling, and even to a stinging as 
by a nettle. The Anthea Cereus possesses the sting- 
ing power in a much greater degree than the ordin- 
ary Actinice. Probably the skin of the human hand 
is in general too thick or hard to be pierced by their 
fine spicula. Dr A. Waller of Birmingham has recently 
found, that, on submitting the tip of his tongue to 
the tentacula, a pungent pain and stinging, as by a 
nettle, were the constant result. He has also found 
that a thin India-rubber membrane grasped by the 
tentacula retains the microscopic ¢poison-darts’ 
sticking on its surface. Some of these are only two 
or three times the length of the capsule which con- 
tains them, or at most 100th part of an inch; but 
others are much longer, and when within the capsule, 
are coiled up after the manner of a watch-spring. 
The capsules are therefore called filiferous or thread 
capsules. This thread is highly elastic, and the 
expulsion of it, as of the shorter spicula, is effected, 
Mr Gosse tells us, by organs having this for their 
special office. 
AN-END, a maritime term relating to the posi- 
tion of any mast or boom when perpendicular to 
the plane of the deck or other level from which 
it springs. When a top-mast is in its proper place 
at the head of the lower mast, it is said to be 
‘an-end.’ 
A'NEROID (formed in an anomalous way from 
Gr. a, priv., and néros, wet), the name given to abaro- 
meter invented by M. Vidi of Paris, in which the 
pressure of the air is measured without the use 
of liquid, as in ordinary instruments. The face of the 
A. barometer, represented in fig. 1, has a diameter 
of about 5 inches, and the case behind, which con- 
tains the mechanism, a general idea of which is 
given in fig. 2, is about 2 inches deep. The pressure 
of the atmosphere acts upon a circular metal box, 
AA, about 3 inches in diameter, and  of an inch 
deep, which has been nearly exhausted of air, and 
then soldered air-tight. The sides are corrugated 
in concentric rings, 8o as to increase their elasticity, 
case which contains the whole. The amount of 
exhaustion is such that if the sides of the box were 
FIGC. 2. 
4/VE RO \© 
   
WD) 
7, \ 
4/ S 
9€/IH[H‘ \91' 
  
  
  
  
  
  
  
Aneroid Barometer. 
allowed to take their natural position, they would 
be pressed in upon each other, and to prevent this 
they are kept distended, to a certain extent, by 
a strong spring, S, fixed to the case, which acts upon 
the head of the stalk, B, attached to the side 
next the face. When the pressure of the air 
increases, there being little or no air inside the box 
to resist it, the corrugated sides are forced inwards, 
and when it diminishes again, their elasticity restores 
them to their former place; and thus the little 
box becomes a spring extremely sensitive to the 
varying pressure of the external atmosphere. Sup- 
posing the two sides pressed inwards, the end of 
the spring, E, will be drawn towards the back of 
the case, and carry with it the rod, EG, which is 
firmly fixed into it. EG, by the link GH, acts on 
the bent lever, HKL, which has its axis at K, so 
that, while the arm, XH, is pushed to the right, 
LK is moved downwards. By this motion, a watch- 
chain, O, attached at L, is drawn off the little drum, 
M, and the index-hand, PP, which is fixed to it, 
would move from the position represented in fig. 1 
to one towards the right. When the contrary 
motion takes place, a hair-spring moves the drum 
and the hand in the opposite way. By this mechan- 
ism, a very small motion of the corrugated sides 
produces alarge deviation of the index-hand, 5}5 of 
an inch causing it to turn through 3 inches. The A. 
barometer is graduated to represent the inches of 
the mercurial barometer, with which, when carefully 
adjusted, it almost accurately corresponds. Both 
from its small size and construction, it is extremely 
portable, and it can in consequence give indigations 
1n circumstances where the ordinary barometer is of 
no service. The ¢ Metallic Barometer’ of M. Bourdon 
is a modification of the ‘A. principle. --See Manual 
of Barometers, by J. H. Belville. 
A'NEURISM (Gr. anewrysma, a dilatation) is a 
pulsating tumour consisting of a sac or pouch into 
which blood flows through an opening in an artery. 
The sac of an arterial A. may be formed in the first 
instance by one or more of the tunics of the vessel, 
generally the outer one, the two inner having given 
way. This is called a true A., in contradistinction 
to the false, in which the sac is formed of cellular 
tissue condensed by the blood flowing into it after 
a wound has been inflicted on the artery from 
without. Should the sac give way, and the blood 
escape among the tissues, the A. is said to be 
diffused. Varicose A. is when the sac communicates 
both with an artery and a vein; Aneurismal Varix, 
when these vessels communicate without any sac 
  
and one of them is fixed to the back of the brass 
intervening ; both of these are generally the results 
251 
  
  
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