360 



Development of the Lymphatic Nodes in the Pig 



same series taken at the level marked h on Fig. 4. Tt corresponds with 

 Fig. 3, and shows a similar relation to the internal jugular vein and the 

 sterno-cleido-nuistoid muscle. It shows that the sac comes nearest the 

 surface between that muscle and the trapezius. It also shows the ex- 

 ternal jugular vein at the anterior border of the sterno-cleido-mastoid 

 muscle and the neighboring plexus of lymph ducts. A section about half 

 way between the letters a and h on Fig. 4 shows the heart near the surface 

 and the duct adjacent to the vein as two distinct cavities. 



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t o 



Keart 



scm 



d/ 



L snvn 



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Fig. 3. Transverse section through the neck of an embryo pig, 2 cm. long, 

 showing the anterior lymph hearts, x 15. Ijv. internal jugular vein; I, 

 larynx; p. pharynx; son, storno-cleido-mastoid muscle; sh, sympathetic nerve; 

 rn. vagus nerve. 



Fig. G is aiiotlier specimen made transparent in potash. It is from a 

 pig 6 cm. ](Mig and is to 1)0 compared with Fig. 5, Vol. Ill, p. 188, which 

 is from a pig 5.5 cm. long. The former shows the lymjDhatics in the 

 depth and tlie latter those of the surface at al)0ut the same stage. The 

 injection for this specimen was made in two places: one just back of the 

 fore leg as marked by the extravasation ; from this injection the ducts 

 over the shoulder, the lymph sac, and two lapge ducts running to the 

 long plexus were filled. The second injection was made l)etween the eye 



