332 DISCOVERY REPORTS 



outwards from the major vessels to various parts of the retial mass. Nowhere, how- 

 ever, was the free flow of blood through any part of the thoracic vascular system, 

 arterial or venous, in any way impeded by the anastomosing strands of the rete. The 

 rete communicated freely with the blood vessels with which it stood in relation, but 

 did not form an integral part of them. 



Wilson (1879) in describing the thoracic rete of the Narwhal distinguished three 

 types of constituent vessels : 



Vasa maxima — vessels of large calibre with thin puckered walls. These were mainly 

 situated in the inferior aspect of the rete towards its posterior extent. 



Vasa media — smaller in calibre than the vasa maxima and more generally distributed 

 throughout the mass. The walls of these were also puckered. 



Vasa minima — much smaller than the preceding with proportionately thick walls. 

 They were found deeply embedded in the rete. 



In the Fin Whale it was not possible to divide the constituent vessels of the rete 

 into three such definite classes: indeed, Wilson stated that intermediate sizes between 

 the three named were found also in the Narwhal. However, in the Fin Whale large 

 venous channels with thin walls were certainly found running through the substance 

 of the mass and these, as will be seen later, tended to converge towards the posterior 

 thoracic vein and thus lay somewhat posterior and inferior in position. These perhaps 

 were the vasa maxima of Wilson. Secondary smaller venous twigs were also seen which 

 may correspond to the vasa media and the main mass of the retia was made up of much 

 smaller vessels with thick walls which may be looked upon as vasa minima. There were, 

 however, an infinity of gradations between the three sizes. The sinuosities of the 

 component vessels of the retia were much too complicated to unravel by dissection. 



POSITION AND RELATION TO MUSCLES 



Some account of the anatomy of the ventral aspect of the neck must be given in order 

 to explain the positions of the various parts of the rete and their relationships. 



The arrangement of the muscles of the neck was found to be the same as that 

 described by Schulte for the Sei Whale (Balaenoptera borealis). 



Schulte says (p. 425) : " In the neck a great muscle complex is formed. . . . The complex 

 is of great size and extends its insertion far upon the basis cranii as well as its origin 

 upon the ribs and spine. From these two sources the fasciculi converge and unite inside 

 the arch of the first rib thus extending as a single mass" — on each side — "to the skull. 

 So that the whole complex has the form of an inverted Y" — on each side — "the 

 diverging arms of which embrace the dome of the pleura and limit its extension 

 rostrad" (Fig. 1). The lateral arm of the Y is the scalene muscle and arises chiefly from 

 the external surfaces of the first three ribs and also in part from the fourth and fifth 

 (Fig. 1). The mesial arm of the Y is divisible into a massive "superficial portion 

 extending from the thoracic (dorsal) vertebrae to the basi-occipital " and a dorsal portion 

 confined to the spine. The superficial and more ventral portion enters into relation 

 with the scalene to form the stem of the Y continuing on to the skull. It was identified 



