19093} ANATOMY OF CERTAIN UNGULATA. 171 
of a peculiar muscle arising from the vertebral column in the 
middle line and running to be inserted on to the cesophagus. 
The direction of the muscle is almost transverse, and it arises 
from the centre of either or both of the seventh and eighth dorsal 
vertebre. It les opposite to the second branch of the azygos 
vein, which in this animal is developed only upon the left side. 
A nearer examination of this muscle where it ends upon the 
cesophagus shows that it is continuous with a distinct and easily 
separable muscular sheath of the esophagus. The muscle is so 
large that it could hardly escape being seen if the thorax of the 
species were examined by anyone. I 1 imagine, therefore, that the 
reason why it is not described by Dr. Garson is that he ‘intended 
to describe it later in the second part of his memoir dealing with 
the bones, the muscles, and nerves of Porcula salvania. After 
finding this peculiar and very obvious muscle in the Pygmy Hog, 
I looked for it in some other Suide, but so far with negative 
results. I did not find the vertebro-cesophageal muscle in 
Dicotyles tajacu, or in Phacocherus cthiopicus. It was also 
apparently absent in a young Sws cristatus, which completes the 
list of Suidee which I have examined up to the present date for 
this particular structure. Nor has a superficial examination of 
other mammals shown anything of the kind to be present. I am 
at least convinced that no such large muscle in the same situation 
or hard by exists in a large number of mammals. Unfortunately 
I neglected to note the minute structure of this muscle. I pre- 
sume, however, from its large size that 1t consists of striated fibres. 
I have described in the heading to this section of the present 
communication to the Society the muscle just described as ‘ new.” 
I believe it to be so. But at the same time something of the 
kind has long been known to exist at any rate in man. 
Thus Prof. Birmingham writes * :—‘ The longitudinal fibres 
[z. e. of the cesophagus] are often joined by slips of unstriped 
muscle, or elastic fibres, which spring from various sources, 
including the left pleura Consaep Cunningham), the bronchi, 
back of trachea, pericardium, aorta, &c. These slips assist in 
fixing the cesophagus to the surrounding structures in its passage 
through the thorax, and have been aptly compared to the tendrils 
of a climbing plant.” It is plain that these shps of muscular 
tissue also correspond to similar slips often very numerous and 
closely adjacent which occur in the corresponding and in other 
situations in the mesenteries of Saurians. A massing of these 
would produce a muscle like that which I have just described in 
Porculay salvania. This subject, however, evidently requires 
further study. All that I can say at present is that there are 
certainly some mammals in which a large vertebro-cesophageal 
muscle like that of Porcula salvania does not exist. 
* Textbook of Anatomy; edited by D. J. Cunningham. London & Edinburgh, 
1902, p. 991. 
+ It is true that Dr. Garson saw no reason in view of the structure of the animal 
for retaining the generic name. I have, however, described a new character which 
may go towards justifying its retention. 
