SCHULTE, SKI WHALE. 409 



tion. Yet in strictness as this is a foetal lung, this could be considered indicative only of the 

 primitive type of breathing of the species and not absolutely of its adult condition which might 

 be adaptively modified. What the adult condition is, both in respect to respiration and to 

 bronchial type is unfortunately not known in such detailed exactitude as is required by this 

 kind of a problem. In this connection a suggestion made by Dr. John C. Vaughan of this 

 department is not without interest and with his permission I state it. When the animal has 

 filled its lungs at the surface and then dives, its thorax and diaphragm are in the position of 

 full inspiration. The position of the diaphragm during submergence is of course a matter of 

 conjecture. But on the assumption that it does not maintain its contraction, it is evident 

 that the pressure of the water upon the abdomen would force the relaxed muscle rostrad in the 

 thorax, and that this would necessitate a redistribution of the air in the lungs entailing a passive 

 movement of the ribs beyond their position in full inspiration. As with the exception of the 

 first, the ribs are free of sternal connections it is conceivable that their ventral extremities might 

 be displaced laterad to a marked degree, even so far as to take up the slack in the ventral pouch, 

 which in this foetus is by no means so baggy over the thorax and abdomen as in the intermandi- 

 bular region. It would seem therefore that Andrews's association of the ventral furrows on 

 thorax and abdomen with respiratory movements has much in its favor and that its plausibilitv 

 is increased by Vaughan 's suggestion of passive distention following a hypothetical relaxation 

 of the diaphragm. 



Sterno-mandibularis and associated muscles. The side of the neck is occupied by a very 

 large muscle mass of complex arrangement which extends from the thorax to the mandible and 

 to the postglenoid region of the cranium, its fasciculi having an obliquely dorso-rostral direc- 

 tion. This muscle which for want of a better name may be called sterno-mandibularis, lies 

 under cover of the panniculus carnosus; its dorsal margin is in apposition with the mastohu- 

 meralis and trapezius; mesad it enters into the boundary of the cavum ventrale and by its deep 

 surface conceals the sterno-mastoid and farther rostrad overlies the caudal portion of the mylo- 

 hoid near the origin of the latter muscle. From its mesal border fasciculi are added to the 

 longitudinal stratum of the ventral pouch, in this as in its nerve supply revealing its provenience 

 from the cervico-hypoglossal musculature. It is not however a modified and extended sterno- 

 hyodeus, for that muscle is present with its usual attachments; it should rather be considered 

 a cleavage product of the infrahyoid group, resulting in the formation of a superficial stratum 

 which has attained enormous size and acquired extensive new origins and insertions. At its 

 origin it is obscurely divided into two heads, partially separated by the rostral border of the 

 pectoralis. The mesal fasciculi arise from the aponeurosis covering the pectoral muscle and 

 on their deep surface receive additional bundles from a narrow strip of sternum between the 

 origins of the pectoralis and sternomastoid. The lateral fasciculi arise from the rostral margin 

 of the first rib near its sternal extremity, here being continuous with the deep origin of the mesal 

 head, further from the fascia of the posterior triangle of the neck, from the sheath of the sterno- 

 mastoid and mesal to this from the sheath of the sterno-hyoid. From this extensive origin 

 the fasciculi are directed dorsad and rostrad, spreading out to form a thick fan shaped sheet 

 which splits into two layers to give passage to the facial nerve. Of the superficial stratum the 

 most mesal fasciculi are continuous with the longitudinal stratum of the ventral pouch. The 

 next pass over the lower border of the rrandible join the panniculus and are inserted into the 

 lower lip, into the floor of the furrow which prolongs the vestibule below the eye, while the most 



