THE VASCULAR SYSTEM 251 



(10—15 mins.) the operation was stopped and all the points of exit 

 sealed (with pyroxylin) so as to prevent leakage, and the animal 

 immersed in 5-10 per cent, formalin overnight to assist in 'setting' 

 the jelly. 



3. Description (Pis. XVIII and XIX). 



For convenience of description the lymphatic system may be 

 divided into the following sections : 



A. Subcutaneous network. 



B. Lymphatics of the limbs. 



C. ,, „ „ pelvic region and tail. 



D. ,, „ ,, trunk and viscera. 



E. ,, ,5 55 pectoral region. 



F. „ „ „ head. 



G. Lymph hearts and their relation to the blood-vessels. 



A. Subcutaneous network. 



In contrast to the Frog there are no extensive lymph-sacs imme- 

 diately under the skin, but, with the exception of a few more or 

 less well-defined areas, the subcutaneous lymphatics form a rich 

 reticulum with irregular meshes. The mesio-ventral portion of the 

 abdomen is very sparsely supplied with lymphatics, which are 

 almost confined to two small longitudinal vessels running along 

 the mesial edges of the M. rectus abdominis superficialis, and re- 

 ceiving lateral tributaries segmentallyat each myoseptum. Posteriorly 

 these vessels join the sub-pelvic plexus, and anteriorly they enter 

 the pectoral network. They represent the trunci lymphatici longitu- 

 dinales parahdominales (Grodzinski in Amblystoma). Lymphatics 

 are also nearly absent from the dorsum of the trunk and tail, but are 

 rich along the sides of the body. 



The sub-pelvic plexus is a rich, subcutaneous network with 

 irregular meshes, extending forwards from the cloaca on the ventral 

 side of the body, between the legs, as far as the anterior end of the 

 ypsiloid cartilage. It covers the pelvic sinuses (see p. 1^'^ and to 

 some extent the inguinal sinuses also. It communicates with the 

 former sinuses on their ventro-mesial aspects at about the level of the 

 transverse axis of the limbs. 



The sub-pectoral plexus similarly underlies the pectoral girdle, and 

 extends from the sternum to the gular fold. It becomes richer and 

 sinusoidal laterally in the region of the arms. 



The sub-maxillary plexus covers the whole of the skin of the mouth- 

 floor, and becomes sinusoidal in the region of the gular fold. In 



