574 
trachea, the inferior thyroid venous 
plexus, on a level with which would be found, 
in rare cases, the middle thyroid artery (of 
Neubauer) ascending from the aortic arch : 
these vessels are covered by a layer of fascia 
dividing them from the sterno-thyroid muscles, 
These are variously involved in the two 
remaining modes of bronchotomy; one of 
which—the tracheal—consists in dividing three 
or four rings of the tube, below the isthmus of 
the thyroid gland; the other—the crico-tracheal 
—in dividing its upper rings and with them the 
cricoid cartilage of he larynx. The first—tra- 
cheotomy—{after a vertical division of the 
tegumentary parts and a separation of the 
muscles from the lower part of the larynx to 
the sternum) exposes the tube in that portion 
of its extent in which it is deepest and most 
nearly related to vessels. The operator is 
required to bear in mind the possible presence 
of a middle-inferior thyroid artery, lest he 
wound it inadvertently; he must avoid, or, 
before opening the air-tube, must secure the 
inferior thyroid veins ; in recollecting the great 
lateral mobility of the trachea and its close 
parallelism to the carotid arteries in the lower 
part of the neck, he must guard against any 
oblique glancing of his knife, by which these 
great vessels might be injured ; in proceeding to 
divide the cartilaginous rings, he must com- 
mence below and on a completely exposed 
part of the tube, and with the blunt border 
of his knife toward the middle line of the 
sternum, and with its point directed slightly 
upward, lest (as might happen in neglect of 
these precautions) the great vena innominata, 
transversely crossing the tube just below the 
level of the sternum, or the large arterial trunks, 
which are there diverging from the median line, 
should sustain injury: nor must he rudely 
transfix the tube and encounter the risk of 
pee ate arts, normally or abnormally be- 
ind it.* The second operation, crico-tracheo- 
tomy, first proposed by Boyer,+ pretends to 
preference over that just mentioned, on the 
ground of obtaining an equally free opening 
with less invasion of important parts. Indeed, 
although M. Boyer, in proposing it, seems to 
have considered the section of the thyroid 
isthmus inevitable, and accordingly included 
its division in his estimate of risks,—perhaps 
even that objection might be withdrawn from 
the operation, if performed in exact agreement 
with his description ; since the finger may de- 
press the thyroid body to an extent which 
* In suggesting the possibility of injuring organs 
abnormally situated behind the trachea, the text 
particularly refers to the occasional passage of a 
right subclavian artery, from the left part of the 
arch, either between the cesophagus and trachea, 
or behind both those tubes. The anomaly is not a 
very rare one ; and a case is reported, in which the 
artery, so running, was pierced by a bone, arrested 
in and perforating the esophagus. ( in Hos- 
pital , vol. ii.) The irregularities of the 
aorta itself, quoted by Tiedemann from Hommel 
and Malacarne, are of almost uniqne occurrence, 
hardly furnishing an additional argument for that 
uniform caution, which the above less infrequent 
abnormality makes imperative. 
+t Maladies Chirurgicales, vol. vii. p. 131. 
NECK. 
. | 
admits a safe division of the first two rings 
the trachea. But it seems to have pi 
notice, while theorising on the operation, t 
a section of the cricoid cartilage must be use. 
less, unless abused ; that a rigid ring, dividi 
at one point of its circumference, remains 1 
loosened ; that a single section of the erie 
cartilage could not made available a 
means for increased access to the air-tube, ov 
and above that afforded by division of th 
chea, except by employing onita disruptivefo 
that should effect a counter-fracture at s 
other part of its circumference. Such viol 
on such an organ M. Boyer was far too ju 
cious a surgeon to have sanctioned ; and { 
the single instance, appended (p.142 bi 
speculations on the subject, it appears probak 
that the upward extension of his opening in 
air-tube was useless; that an incision throu 
the upper rings of the trachea sufficed for | 
escape of the foreign body; and that, in- 
essential particulars, the crico-tracheal ope 
tion is but tracheotomy at a higher than 
nary level, complicated with an unadvantage 
and therefore objectionable intrusion on — 
larynx. 
2. The antero-inferior triangle djoins | 
wardly the space last described, is boun 
outwardly by the decussation of the omo-hy 
muscle (which separates it from the supt 
compartment of the great anterior trial 
with the imaginary diagonal, which demar 
from the postero-inferior or supra-clavic 
space. Its various parts and contents rec 
some separate description. As regards thei 
guments, it will be remembered that the 
tysma only pee? covers this space, and 
the anterior jugular vein, when it exists, is 
tained here in the lower part of its course. - 
sterno-cleido-mastoideus follows the outer 
of the triangle, but extend over it by its 
border, so as to cover a large portion ¢ 
area. Beneath this muscle, the stronge 
layer of the cervical fascia is extende 
splits internally to enclose the sterno- 
deus, which likewise encroaches on the 
by its inner side. Under this fascia the eo: 
carotid artery (beside which are the ji 
vein and the pneumogastric nerve) asee 
tically, and is slightly overlapped from 
by the thyroid body. The anatomy of th 
is well developed, in considering the b 
of reaching the carotid artery: a vertici 
sion falling on the sterno-clavicular j¢ 
poses the superficial fascia and part of t 
tysma; these being divided, the she 
sterno-mastoid is seen, and on its being © 
the sternal fibres of the muscle present 
selves, obliquely ascending outward: 
vision and displacement exposes the p 
layer of their fascial investment, which 
seen to ensheath the sterno-thyroid muse 
descending branch of the lingual nerve 
scendens noni) seems almost embedded 1 
deep layer of the aponeurosis, and reach 
outer edge of this muscle in the upper pi 
the space:—beneath the stratum of par 
constituted, the carotid lies with the associ 
organs: the jugular vein is on its outer” 
