348 CONTRIBUTIONS TO ZOOLOGICAL PATHOLOGY. 
oesophagus, must be carefully removed ; and with a pair of Pares 
forceps, or strong common scissors, the os hyoides should be divided 
at the junction of the cornua with the body, as also the wing of the 
thyroid cartilage external to its mesial ridge. These parts should 
then be removed carefully, without injuring the soft tissues that lie 
immediately within them, and especially taking care of the thyro- 
arytenoideus transversus muscle, which should first be examined 
by drawing the superior border of the thyroid from the cricoid 
cartilage, and after which its origin from the former cartilage 
should be divided so as to enable the parts which have been cut 
through to be removed entirely. This dissection will enable the stu- 
dent to observe the external relations of all the internal set of the 
intrinsic group ; which having been noticed and removed, he can 
then easily examine the arrangement of the various folds of mu- 
cous membrane on the obverse side of the larynx, the chordae 
vocales and the ventricle of the larynx, with the ultimate arrange- 
ment and distribution of the bloodvessels and nerves. 
The crico-thyroideus muscle is situated along the external and 
posterior aspect of the larynx, and arises from the external surface 
of the ring of the cricoid, and, passing obliquely upwards and back- 
wards, is inserted into the inner margin of the posterior border of 
the thyroid cartilage. 
The thyro-hyoideus muscle is placed immediately above and 
before the preceding muscle, and arises from the oblique ridge on 
the external surface of the great wing of the thyroid cartilage, and, 
passing forwards and upwards, is inserted into the inner margin of 
the posterior border of the body and greater cornu of the os 
hyoides. 
The crico-arytenoideus superior, or posticus muscle, is situated 
on the superior surface of the cricoid cartilage beneath the angle of 
junction between the pharynx and the oesophagus, and consists of 
a strong and radiating band of muscular fibres that fill up the fossa 
on either side of its mesial ridge, to which the posterior constrict- 
ors of the pharynx and the anterior fibres of the oesophagus are 
attached. From this broad origin the muscle passes forwards and 
slightly outwards to become inserted into the base of the arytenoid 
cartilage, and also into the tuberculated posterior extremity of the 
prominent ridge along its superior surface. 
The crico-arytenoideus inferior, or lateralis muscle, is situated 
in the upper part of the crico-thyroid space, and arises from the 
anterior margin of the ring-like process of the cricoid cartilage and 
the edge of the crico-thyroid membrane. From these points it pro- 
ceeds upwards and backwards to be inserted into the ridge of the 
arytenoid cartilage along with the former muscle, as also into the 
external arytenoid fossa. 
