248 LECTURE X. 



wards to the interspace of the pectoral fins, where tlie size of the 

 vessel best favours the insertion of the injecting pipe. It receives 

 the lymphatics of the pectorals, and (in thoracic and jugular fishes) 

 of the ventral fins ; then, advancing forwards through the coracoid 

 arch, it spreads out into a rich network, which almost surrounds the 

 pericardium. The lymphatic plexus which covers the heart of the 

 Sturgeon and Paddle-fish presents a spongy and almost glandular 

 appearance when uninjected: large lymphatic trunks from the upper 

 (dorsal) part of this plexus receive the lymphatics of the myocommata 

 by a deep-seated trunk which runs along the ribs, and the lymphatics 

 of the mucous ducts and integuments by a superficial trunk, which ex- 

 tends along the lateral line, and gets a penniform character by the 

 regular mode in which its tributary lymphatics join it. The lym- 

 phatics of the head form minor plexuses at the bases of the orbits, 

 and in the Carp they extend into the basi-cranial canal ; those from 

 the cellular arachnoid pass through the occipital foramen to join the 

 lymphatics of the spinal canal, and terminate in the cervical and 

 sub-occipital trunks, which I'eceive the lymphatics from the upper 

 extremities of the gills : these, with the deep-seated lymphatics from 

 the kidneys, join the single or double trunks at the under part of the 

 vertebral column, which combine with the lacteal plexiform trunks 

 continued forwards along each side of the stomach and oesophagus, 

 to form a large, short, common lacteo-lymphatic trunk on each side, 

 which terminates in the jugular vein near its junction with the short 

 precaval vein. The lymphatic system of the caudal portion of the 

 body is chiefly received by two caudal sinuses, intercommunicating 

 by a transverse canal, which sometimes perforates the base of the 

 anchylosed compressed terminal tail-vertebra, and, converging to 

 enter the ha;mal canal, terminates there in the commencement of the 

 ' vena caudalis.' Dr. M. Hall discovered that the caudal lymphatic 

 sinus, in the Eel, possessed a contractile pulsating power.* P^ohmanf 

 describes other and minor communications between the absorbent 

 and venous system of Fishes. 



The lymphatics of Fishes consist generally of a single tunic ; a 

 most delicate epithelial lining may be distinguished in the larger 

 trunks. The only situations where valves have been seen in these 

 vessels are at the terminations of the trunks in the caudal and the 

 jugular veins. There are no lymphatic glands : these are i-epre- 

 sented by the large and numerous plexuses ; and the whole absor- 

 bent system presents, as might be expected in Fishes, the first step 

 beyond the primitive condition of the common areolar or cellular 

 receptacle of the lymph in the Invertebrata. The chyle, as well as tlie 



* XXXIX. ii. p. 217. -J- cm. 



