PART I 



THE DEVELOPMENT OF THE SYSTEMIC LYMPHATIC 

 VESSELS, IN THEIR RELATION TO THE BLOOD- 

 VASCULAR SYSTEM 



The question as to the origin of the lymphatic vessels has, 

 especially since 1902, occupied the attention of a number of 

 American observers. These investigations have followed the 

 older work on the same subject of Langer ('68), Budge ('80-'87), 

 Gulland ('94), Ranvier ('95-'97) and Sala (1900), and the results 

 have been published chiefly in the American Journal of Anatomy 1 

 and in the Anatomical Record. 4 



During the progress of these researches a number of facts of 

 primary importance bearing on the problem of lymphatic develop- 

 ment and organization have been discovered. Some of these 

 facts have been worked out in detail and are based on sufficiently 

 extensive material and accurate observation to carry con- 

 viction by their constancy and consistency and to warrant their 

 acceptance as definitely established ontogenetic conditions in 

 the mammalian embryo. Other observations still lack complete 

 confirmation, and in some others the methods employed in their 

 determination create a doubt as to their validity, and tend to 

 confuse the subject. Finally there are other conditions concern- 

 ing which there still exists an honest difference of opinion, and 

 which hence require further study and definite determination. 

 On the whole, however, the American work of the last six or 

 seven years has led to considerable and permanent advance in 



1 Vol. i, 1902; vol. iii, 1904; vol. iv, 1904; vol. v, 1905; vol. vi, 1907; vol. ix, 1909; 

 vol. x, 1910 

 4 Vol. ii. 1908: vol, iv, 1910. 



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