122 Journal of Comparative Neurology and Psychology. 



In other regions, the cord is seen very early, including the 

 greater part of the ridge (Fig. 3, Sy.), and appears to be push- 

 ed outward and upward by the ridge, as the latter becomes bet- 

 ter developed; while more frequently the cord is not seen dis- 

 tinctly till the ridge has grown to about half the size to which 

 it finally attains. Between the second nerve and the point 

 where the median dorsal aorta begins (Fig. 9, *), the ridge lies 

 against the aorta (Fig. 5, Rt.). In the region of the kidneys, 

 it extends outward and upward, lying between this organ and 



/T;^. ^. — Transverse section of an 18.5 mm. toad, through the third spinal 

 nerve (see Fig. 10), showing the relation between the sympathetic cord, Sy., and 

 the third spinal nerve, S/>. N. j. The dotted parallel lines indicate the nerve as 

 reconstructed from sections just anterior to the one here represented. For devel- 

 opment of ramus, cf. Fig. 12. Other reference marks, same as in preceding fig- 

 ures. X246. Camera lucida. Reichert, oc. 2, obj. 7 a. 



the notochord (Fig. 6, Rt.). In the structure with which the 

 sympathetic ridge is connected (Fig. 9, Ma.), two changes need 

 to be noted ; first, a general increase in size and second, the ob- 

 scuring of the sympathetic ridge in the region of the fourth 

 nerve, due to relationship with a structure referred to in the 

 preceding stage as being possibly adrenal. 



In regard to the relation between the spinal nerves and the 

 sympathetic, we find short rami in connection with the fourth. 



