1883.] ^^^ i^^^ Morphology of Arteries, especially of the Limbs. 505 



Fig. 15. Canthocamptus, sp. n,, stylets of female. 



" 16. " antenna. 



" 17. " fifth foot of female. 



" 18. Diaptomus ^^ sanguineus,^'' fifth feet of larva ((^). 



" 19. " ^ fifthfeet of larva (9). 



" 20, " abdomen of larva (9). 



•' 21. « fifth foot of adult (^). 



" 22. *' antenna of adult. 



" 23. Diaptomus '■^ castor^'' margin of last segment ((j^). 



" 24. " margin of last segment (9)* 



" 25-28. Cyclops pedinatus. 



" 29. Diaptomus pallidus, inner ramus of fifth foot ( 9 •) 



REMARKS ON THE MORPHOLOGY. OF ARTERIES, 

 ESPECIALLY THOSE OF THE LIMBS.^ 



BY FRANK BAKER, M.D. 



IT is generally taken for granted that the variability of arteries 

 is such that they are of but little use in morphological studies. 

 Anatomists are usually of the opinion that since the function of 

 the arteries is to nourish the tissues, their course from the heart 

 to their destination is of too slight importance to the race to have 

 become a fixed character, and all search for law is abandoned. 

 But it is questionable whether some biologists have not too 

 hastily come to this conclusion. 



Morphological laws are always obscure when studied in the 

 adult individual alone. To trace them we must examine the dif- 

 ferent phases of individual development and investigate the anat- 

 omy of related forms. 



There is a period when the embryo of a vertebrate animal is 

 not provided with a proper vascular system. During the early 

 stages of the segmentation of the ovum, no vessels exist, the 

 young cells receiving the necessary nutriment from an interstitial 

 plasma, as do those of the lowest Protozoa. 



This stage is of short duration. Throughout the minute disk- 

 shaped object which is hereafter to be a fully developed verte- 

 brate, certain cells appear, of a slightly reddish color, dotting 

 the disk in a peculiar marbled manner. From their appearance 

 and isolation these are known as blood-islands. They touch each 

 other finally as they increase in number, either at some part of 



* Abstract of a paper read before the Montreal meeting of the Amer. Assoc, for 

 the Advancement of Science. 



