38 DR D. WATERSTON AND DR A. CAMPBELL GEDDES ON EMBRYO PENGUINS 



SECTION I. SOME PECULIARITIES OF THE CERVICAL PORTION OF THE 



VERTEBRAL COLUMN. 



The cervical vertebrae are thirteen in number : the portion of the vertebral column 

 which they make up is remarkable for the development of its antero-posterior curves. 

 In the lower half there is an extraordinary antero-posterior curve the convexity of 

 which is directed forward ; in the upper half there is a second antero-posterior curve the 

 convexity of which is directed backward. 



These curves are present in all birds ; in none, however, do they approach in intensity 

 the curvatures found in the penguin. The lower curvature is so pronounced that the 

 bodies of the vertebrae come in contact with and fill up the angle formed by the limbs 

 of the clavicle, and, in the living bird, actually cause a projection on the front of the 

 neck. As a result the trachea and oesophagus, instead of passing into the thorax in 

 front of the vertebral column, are pushed away to the right side and actually lie on a 

 plane posterior to the vertebrae of the convexity. The knowledge of this extraordinary 

 condition is not new ; it is fully described by Professor WATSON, but the point seems to 

 have been entirely overlooked, for in all the specimens in museums that we have had 

 the opportunity of seeing the cervical vertebrae are incorrectly mounted. 



Professor MORRISON WATSON was of opinion that these curvatures were associated 

 with the maintenance by these birds when on land of the erect attitude, and that they 

 served to bring the centre of gravity of the head and neck over the base of support 

 formed by the feet. To us it appears more probable that the curvature is useful to the 

 bird when in the water, giving it a greatly increased displacement forward and reducing to 

 a minimum the fatigue of carrying the head and heavy beak in the long ocean voyages 

 which it undertakes. These may apparently be very prolonged, for the birds have been 

 seen no less than 600 miles from land. 



SECTION II. SOME PECULIARITIES IN THE ARRANGEMENT OF THE FASCIAL LAYERS 

 IN RELATION TO THE PECTORAL MUSCLES. 



The most striking feature with regard to the pectoral muscles is their enormous 

 size and power. There are four muscles belonging to this group : first, the pectoralis 

 major; second, the dermo-humeralis (muscle des parures) ; third, the pectoralis medius ; 

 fourth, the pectoralis minor. The origins and insertions of these muscles are given in 

 detail and with great accuracy by Professor MORRISON WATSON. Their action is not 

 without interest. The pectoralis major is divided into two distinct parts : an anterior 

 which arises from the clavicle and from the outer surface of a strong aponeurosis 

 which separates it from the medius and is inserted through a special tendon into the 

 whole length of the anterior or radial margin of the bones of the wing, and by an 

 aponeurotic extension from the tendon which covers both surfaces of the wing and 

 conceals the blood-vessels and nerves, and a posterior which terminates in a V-shaped 



(ROY. 8OC. EDIN. TRANS., VOL. XLVIL, 224.) 



