DISTRIBUTION OF LYMPHATICS IN SCOK I'. 1. \ K IITII YS 53 



larger (Figs, i, 2, ia and 4, I.P.S.). It follows along the 

 base of the fin between the superficial and profundus adductor 

 muscles, having blind sacs that pass between the profundus 

 adductor muscles, but which send up short branches between 

 the middle rays that soon fork to anastomose with the corres- 

 ponding branches of its fellow, thus forming a circle over the 

 bases of the middle rays (Fig. 2). These circular vessels re- 

 ceive short pectoral-ray vessels (Figs. 2 and 2a, P.F.L. V. 0) ), 

 which run along the inner surface of the rays. They are much 

 shorter than the main pectoral fin or pectoral fin-ray vessels, 

 but appear in a well-injected specimen to have communicating 

 branches with the main pectoral-ray vessels. The outer pec- 

 toral sinus (Figs. 1 and 2a, O.P.S.) occupies a similar posi- 

 tion between the superficial and profundus pectoral abductor 

 muscles. It also sends back little pockets between the bundles 

 of the profundus muscle, and receives dorsad a large branch 

 that has its origin from the superficial and profundus abductor 

 muscles (see Fig. 1). The outer pectoral sinus, after curving 

 over the most dorsal ray, joins the inner pectoral sinus in form- 

 ing a common trunk that empties into the main pectoral sinus. 

 In addition to these 2 pectoral sinuses there is a third or median 

 pectoral sinus (Fig. 2a, M.P.S.), which traverses the basal 

 canal of the pectoral rays. 1 This trunk receives the main pec- 

 toral Jin or the main pectoral Jin-ray vessels (Figs. 2 and 2a, 

 P.F.L. V.). Two such vessels accompany each ray and receive 

 the network from the pectoral fin membrane. As is shown in 

 Fig. 2a numerous cross-branches pass between the rays from 

 the median pectoral sinus to both the inner and the outer pec- 

 toral sinuses. 



Very little is to be found in the literature on the lymphatics 

 of the pectoral fin. Hyrtl (7, p. 234) says that a pectoral sinus 

 and its branches are filled in a successful injection of the lateral 

 trunk. Stannius (24, p. 253) briefly describes a sinus at the 

 base of the pectoral which receives numerous branches from the 

 pectoral fin muscles. Hopkins simply states with Amia. (8, 

 p. 371) that the lateral trunk receives the pectoral sinus. Trois 

 (28, p. 8, and 29, p. 25) says that in Lophius and Uranoscopus 



1 See note, page 45. 



