9 8 
MAMMALIAN ANATOMY 
Note that a fragment of lung tissue from which the air has been 
driven by pressure between the fingers, still contains so much air 
in its alveoli that it will float when placed in water. Finally 
detach the lungs and trachea from the heart and its large blood 
vessels by severing carefully, one by one, the pulmonary veins 
and arteries at a point as far distant from the heart as possible. 
Discard the lungs and preserve the heart for later study, either 
in cold storage or in 5% formalin. 
Examine with the microscope (Dem. SI. Coll.) cross sections 
of the trachea showing the cartilaginous rings of the walls and 
the ciliated epithelial lining; and sections through the lung 
showing the alveoli inflated, and their relation to the bronchioles 
which lead into them. Draw whatever you are able to identify in 
the way of details from these sections. 
B. THE LARYNX. (Cf. compare with dissections and models 
of the human larynx.) 
Note that the larynx is a differentiation of the anterior region 
of the trachea. In the walls of the larynx locate, by palpation, 
the broad thyreoid cartilage on the ventral and lateral sides, the 
signet-ring shaped cricoid cartilage with its narrow portion 
posterior to the thyreoid and its broad portion dorsal to it, and 
the pair of arytasnoids which project anteriorly, one upon each 
side, between the lateral borders of the thyreoid and the broad 
dorsal region of the cricoid. 
Note that the hyoid bone lies immediately anterior to the 
thyreoid cartilage, and serves as attachment for numerous muscles 
which are not associated with the larynx; the cut ends of these 
muscles are here seen, and should be carefully removed so as to 
expose the external surface of the hyoid bone, the relation of which 
to the thyreoid cartilage will then be made clear. In this dissec¬ 
tion preserve, if possible, the chain of ligaments and cartilages 
which serves to attach each of the lesser cornua of the hyoid to 
the skull, thus suspending the tongue and the larynx from the 
skull (see p. 95). 
By the usual method of dissection of muscles work out the 
musculature of the external (ventral and lateral) surface of the 
larynx, identifying (1) the pair of thyreohyoid muscles which lie 
