CLELAND ON RIES AND TRANSVERSE PROCESSES. 
127 
Seen from this point of view, the question whether the inferior 
limb of origin of the mammalian cervical transverse process is to be 
accounted transverse process or rib, is little more than a dispute of 
words. The fact stands simply thus: that the structure in question 
belongs to the primary circle, and that, as was particularly observed 
by Meckel, it sometimes contains a special centre of ossification. In 
the sacrum there are centres of ossification so independent and con¬ 
stant that they may be with much less hesitation compared to ribs. 
We are now enabled also clearly to see that, although, as has 
been shown, the mammillary, accessory and transverse process of the 
lumbar region are all represented, in the human subject, in the 
extremity of the transverse process of the dorsal region, the main part 
of the latter is purely transverse in its nature, inasmuch as the cha¬ 
racteristic property of a transverse process of the trunk is to take 
part in the formation of the primary circle. 
It may still be objected by the upholders of August Muller’s 
theory, that, after all, the mammalian ribs and transverse processes 
correspond to the upper row of ribs and transverse processes in 
fishes; that what constitutes the lining wall of the fish’s abdomen is 
to be sought in higher animals in the fascia on the ventral aspect of 
the muscles inside the ribs; which muscles, he considers, represent 
the mass inferior to the lateral intermuscular septum in fishes. 
This view of the correspondences of muscles, however, will not 
stand close scrutiny. In the Saurian tail the lateral intermuscular 
septum is found as in fishes. The muscles superior to it are, as 
August Muller rightly observes, continued into the muscles of the 
back ; but the muscles below that line cannot be justly described as 
continued into the interior of the visceral cavity; the superficial ones 
are attached to the pelvis, and continuous with them in front of the 
pelvis are those muscles of the abdomen which lie superficial to the 
ribs; among others the rectus, which can already be easily distin¬ 
guished in some fishes. When the forepart of the tail is laid open, 
we find, indeed, two masses of muscle continued into the abdominal 
cavity, and which, as was shown by Professor Groodsir,* are enclosed 
in the continuation backwards of the lining membrane of the abdo¬ 
men ; but that that membrane corresponds not to the lateral inter¬ 
muscular septum of the fish, but to the lining membrane of the fish’s 
abdomen, is proved by the co-existence of the lateral intermuscular 
septum, which finds its way to the skin as in fishes.fi Porward in 
the trunk there are both infra-costal and transversi-abdominis muscles 
* Edin. New Philos. Journal, Jan. 1857, p. 128. 
t In some reptiles, the prolongation backwards of the abdominal membrane so 
well seen in the crocodile is not brought to a point, but is lost among the muscles of 
the tail with whose segmented mass the included muscles are also blended. Thus 
also, the abdominal cavity in birds and mammals is always incompletely bounded 
behind. 
