DEVELOPMENT OE THE BLOOD VESSELS IN THE EKOG. 187 



we have chiefly employed borax carmine, but in some cases have 

 obtained very excellent results with aniline blue-black, after harden- 

 ing with corrosive sublimate. 



The figures illustrating this paper are in almost all cases dia- 

 grammatic, inasmuch as each has been constructed by combining a 

 number of camera drawings of separate sections, so as to include 

 parts situated at different levels. Considerable pains have been 

 .taken in each case to represent the shapes and positions of the 

 parts shown as correctly as possible. 



HISTORICAL ACCOUNT. 



"We do not propose to attempt an exhaustive consideration of the 

 literature bearing on our subject. A few of the more important 

 memoirs will alone be noticed here, and reference will be made from 

 time to time in the text to the statements and conclusions of other 

 investigators. 



Of the earlier accounts of the development of the blood vessels in 

 Anura, by far the most important is that of Eusconi,* who, relying 

 entirely on dissections and on examination of living specimens, 

 succeeded in determining a number of difficult points, and whose 

 descriptions have afforded the basis for the accounts given by all 

 writers until very recent times. Eusconi distinguished between the 

 afferent and efferent branchial vessels in each arch, naming them 

 " arteres transitoires " and " arteres permanentes " respectively, and 

 describing carefully and correctly their positions in the arches and 

 in the gill loops, and their relations to the vessels of the adult frog. 

 He described and named the "filters " on the gill arches, and noted 

 the comparatively late appearance of the fourth aortic arch, and 

 the development from it of the pulmonary artery. He was wrong, 

 however, in describing the afferent and efferent branchial vessels 

 of each arch as remaining in direct communication with each other 

 throughout tin; whole larval period. 



Ecker,1 in his " Icones Thysiologicic," gives a couple of figures, 

 but no detailed description of the blood vessels of the tadpole. 



* Rusconi, M., "DeYeloppement dela Grenouille commune depuia le moment de 



la Dai iinni: jus'|u<: :i on rtut, pa [Tail ," Milan, IH2G, pp. 47-55. 



| Ecker, " Icones Pbysiologicte," Leipzig, 1851-09, 



