THE VASCULAR SYSTEM 255 



The TT. lymph, long, laterales extend right along either side of the 

 body from a short distance behind the sacrum to the posterior border 

 of the scapula. They lie in the sulci laterales. In the larva they form 

 fairly straight and well-defined vessels, but in the adult they assume 

 a more zigzag course and are only distinguishable as larger vessels 

 among the general lateral network. They are associated with the 

 lateral lymph hearts, and through them discharge their lymph into 

 the lateral veins. They are in communication posteriorly with the 

 iliac sinuses by means of the subcutaneous network, while anteriorly 

 they enter the subscapular sinuses. The relations between these 

 trunks and the lymph hearts is further discussed on p. 260. 



The TT. lymph, long, suhvertehrales. Panizza supposed that the 

 subvertebral lymphatic stem consisted of but a single trunk. Rus- 

 coni assented to this and said that the dorsal aorta and the vessels 

 arising therefrom were totally surrounded by a lymph space as a 

 finger is by a glove, and that the arterial walls were attached to the 

 walls of the lymphatic vessel by fibrous bands. Meyer was of the 

 same opinion. The dorsal aorta was thus supposed to be freely sus- 

 pended in a lymph sinus. These earlier authors had not seen the 

 caudal section, which was discovered later by Favaro. 



By studying the larva Hoyer and Udziela showed that the sub- 

 vertebral space is really to be regarded as a double trunk lying on 

 either side of the aorta, the two elements of which are in frequent 

 communication with one another by means of bridging vessels which 

 pass both dorsal and ventral to the aorta. In the section between the 

 kidneys the latter become so extensive as to give the appearance de- 

 scribed by Rusconi. At about the level of the posterior extremity of 

 the stomach, i.e. at the level of the pylorus, there is a large lymph sac 

 extending ventrally between the mesenteric laminae — the cisterna 

 linfatica (Panizza), while one limb of it extends into the ligamentum 

 gastro-lienale. Into this sac the lymph from the whole gut drains, 

 being carried thither by a number of small lymphatic vessels which 

 run on either side of the blood-vessels. The lymph capillaries within 

 the gut-wall are definitely external to the blood-vessels and they are 

 arranged in different patterns, each characteristic of some particular 

 region of the gut. On the stomach they form a fairly coarse, irregular, 

 brick-like meshwork; on the duodenum and intestine they are 

 arranged in a number of more or less parallel rows connected by 

 bridge pieces so as to give a ladder-like appearance, while on the 

 rectum the pattern assumes that of a rich small-meshed network. 



From the subvertebral stem there are extensive lateral communi- 

 cations with what may be described as the renal sinuses. 



