86 Florence R. Sabin. 



jugular sac is particularly striking. In one section, one of these 

 ducts measures 2.75 x .5 mm. When it is considered that these 

 vessels are really capillaries, being lined by a single layer of endo- 

 thelium, one sees that they are really enormous in size, almost as 



Fig. 17. Sagittal section of a human embryo measuring 50 mm., Mall 

 collection, No. 96, showing the posterior lymph sac within the pelvis and 

 its extension along the femoral vein, x about 8. F., femur ; Lg., lympho- 

 glandula (femoralis) ; O. s.,.os sacrum; S. 1. p., saccus lymphaticus posterior 

 with lymph node in the border ; V. s., vena sciatica ; V. 1. v., vertebra lum- 

 balis V. 



big as the inferior vena cava itself. In general, the Ijonphatic 

 vessels are considerably larger than the blood capillaries. 



The cisterna chyli could not be found in IvTo. 95, but there is a 

 small lymph node near its usual location and there is a thoracic 

 duct. The second embryo (No. 96) was damaged at the area; the 



