Earliest Blood Vessels in Anterior Limb Buds. 



313 



embryos of tlie pig. Embryos young enough to show the earliest 

 conditions in the arm bud are not common, and to supplement this 

 material I have been fortunate enough to examine several perfect 

 series of rabbit embryos from the Harvard Embryological Collec- 

 tion through the kindness of Professor Minot. The latter embryos 

 are all the more interesting since they were the types chosen in the 

 compilation of the "Normal Plates on the Development of the 

 Rabbit" by Minot and Taylor. ^^ Thus the stages of development 



Fig. 17. — Reconstruction of the position and conrse of the segmental sub- 

 clavian arteries present in a rabbit embryo of the tenth day, No. 559 Harvard 

 Embryological Collection. 



may be accurately known from the various details listed opposite 

 them in the latter, work. They comprised embryos designated as 

 E"os. 562, 559 and 556 and in the "Normal Plates" are given the 

 table numbers, 10, 11 and 12. I shall describe these very briefly. 



Embryo 562 has the limb buds as mere swellings of the soma- 

 topleure. On the left side, one could not be certain of the existence 

 of any subclavian capillaries, but on the right side, a subclavian 

 is present midway between the sixth cervical and the seventh cervical 

 segmental vessels. 



"Minot and Taylor. "Normal Phites on the Development of the Rabbit." In 

 the series edited by Keibel. 



