188 
NATURE 
[Fuly 6, 1871 

(as shown in Fig. 1) a faint surface of demarcation ap- 
pears, constituting the boundary between liquid and gas, 
but at first wholly devoid of curvature. We must, how- 
ever, take care not to ‘suppose that a cloud necessarily 
precedes the formation of true liquid. Ifthe pressure be 
sufficiently great, no cloud of any kind will form.” 
After describing the results obtained by the lecturer 
with carbonic acid under varied conditions of tempera- 
ture and pressure, of which a full account has already 
appeared in NATURE,* Dr. Andrews remarked that it 
would be erroneous to say that between liquid and gas 
there exists one intermediate state of matter, but that it 
is correct to say that between ordinary liquid and ordinary 
gas there isan infinite number of intermediate conditions 
of matter, establishing perfect continuity between the two 
states. Under great pressures the passage from the 
liquid to the gaseous state is effected on the application 
of heat without any break or breach of continuity. A 
solid model, constructed by Prof. J. Thomson, from the 
data furnished by the experiments of the lecturer, exhi- 
bited very clearly the different paths which connect the 
liquid and gaseous states, showing the ordinary passage 
by break from the liquid, as well as the continuous pas- 
sages above the critical point. 
After referring to the experiments of Frankland on the 
change produced by pressure in the spectrum of hydro- 
gen, and to those of the same able chemist and Lockyer 
on the spectrum of the spark in compressed gases, Dr. 
Andrews described the remarkable change from a trans- 
lucent to an opaque body, which occurs when bromine is 
heated above the critical point; and then drew attention 
to the general fact that when the critical point is reached, 
the density of the liquid and gas become identical. 
In order to establish the continuity of the solid and 
liquid states, it would be necessary in like manner, by 
the combined action of heat and pressure, to obtain the 
solid and liquid of the same density and of like physical 
properties. To accomplish this result would probably re- 
quire pressures far beyond any which can be reached in 
transparent tubes, but future experiment may show that 
the solid and liquid can be made to approach to the re- 
quired conditions. 

ON AN ADDITIONAL TRUE RIB IN THE 
HUMAN SUBF ECT 
HE almost absolute rule that there are seven true ribs 
in the human subject has, like every other rule, its 
exceptions. Occasionally instances are met with in which 
there are eight sternal ribs on one or both sides. But 
Nature does not effect her evolutions by fer sa/tum transi- 
tions between extreme points, but steadily makes pro- 
gress by degrees almost imperceptible to human intelli- 
gence. So in the matter of rib transition, there are various 
grades met with between the presence of a complete eighth 
sternal rib on the one hand, and its absence on the other. 
In the sternum of a female subject recently dissected at the 
Royal College of Surgeons, the right seventh and eighth 
rib cartilages blended together about a quarter of an inch 
distant from the mesosternum. On the left side the eighth 
rib cartilage was arrested about an inch and a half from 
the mesosternum. The latter was free at its sternal end. 
In anvther subject—a moderately muscular male—the 
eighth rib cartilage on the right side extended within an 
inch of the mesosternum, its extremity being free. On 
the left it was aborted at the distance of two and a half 
inches from the mesosternum. In the latter subject the 
sternum was exceedingly large; all the rib cartilages, 
especially the seventh on the left side, were well developed, 
and the xiphisternum was very much elongated, spatulate, 
and curved in an anterior direction, Occasionally 
See NaTuRE, vol. ii. p. 278, 


specimens are met with in which the sixth rib cartilage is 
implanted upon the distal extremity of the mesosternum 
(rather than upon its distal lateral aspect), lying in front of © 
the xiphisternum, and separated from its fellow of the 
opposite side bya small interval. In the receding angle 
formed by their divergence, the seventh sternal ribs are 
placed, lying directly upon the xiphisternum, and articu- 
lating with it, barely attaining an attachment to the meso- 
sternum. This closely simulates the arrangement met 
with when the eighth sternal rib is present. 
In another adult male skeleton, I found a complete speci- 
men of an eighth sternal rib, but only on the right side. It 
articulated with the xiphisternum, and not with the meso- 
sternum. On the left side the seventh sternal rib cartilage 
was larger than the corresponding one on the right side, 
and articulated with both the mesosternum and xiphi- 
sternum.* 
On examining the skeletons (human) in the Hunterian 
Museum, I noticed another instanceof an eighth sternal rib 
in an adult male African negro, occurring on the right side 
only. It was in every respect similar to the preceding. This 
is the only instance out of the fifteen skeletons (human) con- 
tained in the museum which deviated from the average 
standard number of seven true ribs. It is just possible 
that it may be more frequently present and remain unde- 
tected. In maceration the cartilages are very frequently 
removed, and articulators prepare artificial ones in their 
place corresponding to the average seven. 
On examining the higher quadrumana, &c., I noticed 
that this additional true rib was present only in one young 
chimpanzee, but not in the gorillas and orangs. It was 
present in the gibbon and silvery gibbon, the pig-tailed mon- 
key, Macacus Rhesus, Galeopithecus, and Indri. The aye- 
aye, the slender lemur, and the squirrel monkey, have each 
nine true ribs, The grand galago, the awantilo, the slender 
loris, the douroucouli, and the potto, have each ten true 
ribs. Prof. Flower very kindly called my attention toa 
paper on the axial skeleton of the Primates by Mr. St. 
George Mivart,} in which these rib variations are de- 
scribed as follows: — “In the highest forms of the 
Primates, the number of true ribs is seven, but in 
Hylobates there are sometimes eight pairs. In Sem- 
nopithecus and Colobus there are generally seven, 
but sometimes eight pairs of true ribs. In the Cyno- 
pithecinze the normal number is eight. In the Cebidze 
there are generally seven or eight pairs, but in Ateles 
sometimes nine. In Hapale there are sometimes as few 
as six, sometimes as many as eight; seven or eight in 
Galago, Lemur, and Indris; nine in Cheiromys. The 
highest number, as might be expected, is found in the 
Nycticebine, there being as many as ten pairs of true 
ribs in Perodicticus and Loris.” 
Professor Flower remarks { that “in the higher Simiina 
the ribs do not differ very notably from those of man, 
except in number ; but in the lower forms, and especially 
in the Lemurina, they more resemble those of the Car- 
nivora.” 
In the Carnivora the number of nine sternal ribs is 
fairly constant. There are some exceptions, however, e.g. 
the Esquimaux dog—the Arctic wolf and Proteles have 
only eight true ribs. The common badger (eles taxus) 
has ten true ribs—the tenth rib being implanted on the 
apex of the xiphisternum. The ninth rib in all these 
animals is more or less intimately associated with the 
xiphisternum, but rarely forming so decided an articula- 
tion with it as in the badger. - 
In a dog’s sternum lately in my possession, the xiphi- 
sternum had the ninth rib articulated directly with it. 
* This does not obviate the rule laid down by Prof. Flower in his recent 
admirable book on the Osteology of the Mammalia, that the xiphisternum 
never carries any true rbs. This isthe average rule. But variations are 
frequent, although they cannot be considered in a text-book on average, and 
notirregular, Osteology. 
+ Proceedings of the Zoological Society of London June 27, 1865. 
1 Osteology of the Mammalia, p. 89. 
a 
