184 George 8. Huntington and Charles F. W. MeClure. 
We now pass to a consideration of Lewis’ investigations upon the 
development of the mammalian jugular lymph sacs. 
Lewis is unquestionably the first investigator to furnish the 
clue for the proper interpretation of the development of the 
mammalian jugular lymph sae. In the summary of -his paper 
(p. 110) he states that the lymphatic system begins along the in- 
ternal jugular vein as a detached sac formed by the coalescence 
of several venous outgrowths. This sac, after uniting with other 
independently derived lymphatics to form a continuous system, 
acquires a new and permanent opening into the vein near the 
subclavian termination. 
Lewis’ paper deals chiefly with a description of stages in which 
the jugular lymph sacs have already been formed. Only two em- 
bryos are figured and described by him in which there appears to 
be any evidence whatever that the lymph sac is derived from the 
veins, and, on the basis of these two embryos his above-mentioned 
conclusions concerning the development of the jugular sac were 
apparently formed. These are two rabbit embryos measuring 
9.5 and 10 mm., respectively, in length and concerning which he 
writes as follows: 
In a rabbit of 13 days,9.5 mm., no lymphatics could be found. The 
reconstruction, fig. 1, shows the veins along which the first lymphatics 
are soon to appear. The internal jugular vein receives a great many small 
branches. One of these, nearly parallel with the dorsal border of the 
vein and wider than the others, opens into the vein at either end. It is 
in relation with the third cervical nerve. From its position and appear- 
ance it is believed that this branch of the vein becomes a lymphatic 
vessel (p. 98). 
The second reconstruction is a 10 mm. embryo of 14 days. In this 
specimen a chain of lymphatic spaces has appeared along the internal 
jugular and the dorsal root of the primitive ulnar veins. The most an- 
terior segment of the chain extends back to the third cervical nerve. It 
sends out short blind sprouts like a vein and contains many blood cor- 
puscles. The partition between it and the jugular vein is very thin, and 
at one point there is a suggestion of communication between the two, as 
shown in the figure. No opening into the vein can be demonstrated, 
9 Loe. cit. 
