390 



Harbiet Lehmann, 



Text-Fig. C is taken. This figure is interesting, historically, as being the 

 first to illustrate the transformations of five pairs of aortic arches. It may- 

 be compared with the diagram of Buschke (Text-Fig. B), and Thompson 

 (Text-Fig. E), especially with reference to the origin of the subclavians 

 and the pulmonary arteries. None of these figures show external carotids. 

 Again, in 1837, von Baee published a diagram (Text-Fig. D) 

 showing the transformations of the aortic arches in mammals. 



Ufit^ 



Fig. D. 



Fig. E. 



Fie-. C 



Fig. C. Earliest published Fig. designed 

 to show the transformation of the aortic arches 

 in the bird. After von Baer, in: Buedach, 

 Physiologie, 1827—28. 



Fig. D. Von Baer's diagram, published 

 1837, showing transformation of the aortic 

 arches in mammals, a aortic stem, ft, h aortic 

 roots, c carotid, a, e arteries to the head. 



Fig. E. Thompson's diagram, published 

 1830, to show the transformation of the aortic 

 arches in mammals. A ductus arteriosus just 

 formed. 



In 1830 Allen Thompson illustrated the aortic arches in mammals 

 as shown in Text-Fig. E. This diagram is similar to that of VON Baer 

 for the bird, but presents an original view of the formation of the ductus 

 arteriosus, "by a communication which remains in the bulb of the aorta 

 between the roots of the pulmonic and systemic trunks". This feature of 

 Thompson's diagram is based upon observations of Meckel, and in a 

 note appended to his paper, he states that studies of his own have led 

 him to believe this view to be incorrect, and that the ductus arteriosus 

 in mammals is formed from the left fifth arch. He also confirms from 

 his own observations, the statement of Serres and other observers, that 

 in the early history of the chick embryo, the two aortae are separate 

 throughout their course. 



Thompson's paper consists chiefly of a review of the knowledge on 

 the development of the vascular system to that date, and a large number 

 of his figures are copied from other authors. His statement that five 

 pairs of vascular arches exist for some time simultaneously, in mammals, 

 is rather notable. 



Bathke (1843, 1857), by covering the entire field in his observations, 

 contributed greatly to our knowledge of the aortic arches in the higher 



